JP7682314B2 - Solder jet evaluation device and evaluation system - Google Patents

Description

This disclosure relates to a solder jet evaluation device and evaluation system.

Equipment that uses a jet of molten solder to solder electronic components to printed circuit boards is commonly used on production lines. With such soldering equipment, the contact state of the solder jet with the printed circuit board on which the electronic components are mounted affects the soldering quality. For this reason, in order to avoid the occurrence of defective products, it is necessary to properly evaluate the state of the solder jet when manufacturing printed circuit boards.

For example, Japanese Patent Laid-Open Publication No. 10-193092 (Patent Document 1) describes a solder jet control device that jets molten solder upward from a nozzle in a solder bath and photographs the contact state between the solder jet and the plate-shaped member while the jetted solder is in contact with a plate-shaped member placed above the nozzle. Furthermore, in Patent Document 1, the photographed image is subjected to signal processing to detect the contact width between the solder jet and the plate-shaped member, and the rotation speed of the solder jet pump is controlled to stabilize the detected contact width.

Japanese Patent Application Publication No. 10-193092

In Patent Document 1, the plate-shaped member is made of heat-resistant glass or heat-resistant resin. When heat-resistant glass is used, the image of the solder jet and the contact of the plate-shaped member is taken by a CCD (Charge Coupled Device) camera, and when heat-resistant resin is used, the image is taken by an infrared camera.

However, when the contact state between the heat-resistant glass plate and the solder jet is photographed using a CCD camera, partial halation may occur in the photographed image, making it difficult to evaluate the contact state between the heat-resistant glass plate and the solder jet through image processing. Specifically, partial halation is caused by the presence of air bubbles due to the flux between the heat-resistant glass plate and the solder jet, and spaces due to the three-dimensional undulating shape of the solder jet.

On the other hand, when capturing an image of the contact state between the heat-resistant resin and the solder jet using an infrared camera, there is a concern that due to the high thermal resistance of the heat-resistant resin, a time loss will occur before the temperature distribution on the image captured by the infrared camera shows the contact area between the heat-resistant resin and the solder jet. As a result, there is a risk that it will be difficult to evaluate the contact state between the heat-resistant resin and the solder jet using image processing.

This disclosure has been made to solve these problems, and the purpose of this disclosure is to provide an evaluation device and evaluation method that can stably evaluate the state of the solder jet, as well as to provide a stable method for manufacturing printed circuit boards that avoids soldering defects.

According to one aspect of the present disclosure, there is provided an evaluation device for a solder jet used in a soldering apparatus, the soldering apparatus comprising a molten solder bath from which a solder jet is ejected, a transport conveyor for transporting an object to be soldered so as to pass above the molten solder bath, and a temperature distribution measuring device for an object passing above the molten solder bath. The evaluation device has a transport member and a thin plate member transported on the transport conveyor. The thin plate member is attached to the transport member at a position above the molten solder bath where it comes into contact with the solder jet. The thin plate member is configured so that, when it comes into contact with the solder jet, the rate of heat transfer by thermal conduction within the thin plate member is higher than the rate of heat transfer by heat transfer from the solder jet to the thin plate member.

According to another aspect of the present disclosure, a method for evaluating a solder jet includes the steps of: acquiring a thermal image showing the temperature distribution within the surface of the thin plate member by measuring the thin plate member with a temperature distribution measuring device as the evaluation device according to the present disclosure passes above a molten solder bath; and judging whether the state of the solder jet is good or bad based on the state of the temperature distribution within the surface obtained by image processing of the thermal image.

According to yet another aspect of the present disclosure, a method for manufacturing a printed circuit board includes a step of evaluating a solder jet of a soldering device using a solder jet evaluation method according to the present disclosure, and a soldering step of passing a printed circuit board above a molten solder bath of the soldering device using a transport conveyor. The soldering step is performed after the quality of the solder jet state is determined in the evaluation step.

According to the present disclosure, an evaluation device and evaluation method are provided that can stably evaluate the state of a solder jet based on the temperature distribution in a horizontal plane of a thin plate member or a solder jet measured by a temperature distribution measuring device, and a stable manufacturing method for a printed circuit board that avoids soldering defects can be provided by providing a soldering process after the evaluation.

1 is a conceptual perspective view illustrating a configuration of a soldering apparatus to be evaluated by a solder jet evaluation apparatus according to an embodiment of the present invention. FIG. FIG. 13 is a conceptual perspective view for explaining the operation during an evaluation test of a solder jet according to the present embodiment. FIG. 13 is a block diagram illustrating an example of a configuration for image processing in an evaluation test of a solder jet according to the present embodiment. FIG. 3 is a perspective view illustrating a configuration example of the evaluation device shown in FIG. 2 . FIG. 4B is an exploded view of the evaluation device shown in FIG. 4A. FIG. 3 is a plan view illustrating a configuration example of the evaluation device shown in FIG. 2 . 1 is a graph showing an example of the relationship between the material and thickness of a thin plate and the Biot number. FIG. 2 is a conceptual first cross-sectional view of a thin plate in contact with a solder jet; FIG. 2 is a conceptual second cross-sectional view of the thin plate in contact with a solder jet. FIG. 13 is a perspective view showing a first modified example of the configuration of the conveying member. FIG. 11 is a perspective view showing a second modified example of the configuration of the conveying member. 1 is a first conceptual diagram illustrating an evaluation test performed by the solder jet evaluation device according to the first embodiment. FIG. 11 is a second conceptual diagram illustrating an evaluation test using the solder jet evaluation device according to the first embodiment. FIG. FIG. 9C is a conceptual diagram illustrating the temperature distribution in a thermal image obtained in the state of FIGS. 9A and 9B. 13 is a conceptual diagram illustrating an example of processing a thermal image obtained in an evaluation test of a solder jet according to the second embodiment. FIG. FIG. 13 is a conceptual diagram illustrating an example of setting an inspection frame within a processed thermal image. 11 is a conceptual diagram illustrating an example of setting a quantitative parameter value for evaluating the state of a secondary jet. FIG. 11A and 11B are conceptual diagrams for explaining examples of defective determination from thermal images. FIG. 2 is a conceptual perspective view of a soldering device to be evaluated. FIG. 15 is a cross-sectional view of FIG. 14 when the solder jet is normal. FIG. 16 is a first cross-sectional view taken at the same position as FIG. 15 for explaining a cause of an abnormality in solder jet. FIG. 16 is a second cross-sectional view taken at the same position as FIG. 15 for explaining the cause of an abnormality in solder jet. FIG. 16 is a third cross-sectional view taken at the same position as FIG. 15 for explaining the cause of an abnormality in solder jet. 11 is a flowchart illustrating a method for evaluating a solder jet and a method for manufacturing a printed circuit board according to a third embodiment. 13 is a conceptual diagram illustrating an example of an evaluation model used in the solder jet evaluation method according to the third embodiment. FIG. 13 is a conceptual diagram illustrating an example of regression prediction by the solder jet evaluation method according to the third embodiment. FIG. 11 is a conceptual cross-sectional view for explaining a first example of the shape of a solder jet in a vertical cross section in the transport direction. FIG. 13 is a conceptual cross-sectional view for explaining a second example of the shape of a solder jet in a vertical cross section in the transport direction. FIG. 13 is a conceptual cross-sectional view for explaining a third example of the shape of a solder jet in a vertical cross section in the transport direction. FIG. 1 is a conceptual cross-sectional view for explaining a first example of a cross-sectional shape of a solder jet when a printed circuit board is not passing through; FIG. 23B is a conceptual cross-sectional view for explaining the contact state between the solder jet and the printed circuit board shown in FIG. 23A. 11 is a conceptual cross-sectional view for explaining a second example of the cross-sectional shape of a solder jet when a printed circuit board is not passing through. FIG. 24B is a conceptual cross-sectional view for explaining the contact state between the solder jet and the printed circuit board shown in FIG. 24A. FIG. 2 shows a first example of a thermal image of a solder jet and corresponding cross-sectional profile. FIG. 13 shows a second example of a thermal image of a solder jet and corresponding cross-sectional profile. 1A and 1B are conceptual cross-sectional views illustrating the relationship between the cross-sectional shape of a solder jet and the radiant energy to an infrared camera. 1A and 1B are conceptual cross-sectional views illustrating the relationship between the cross-sectional shape of a solder jet and the temperature detected by an infrared camera. 10 is a conceptual cross-sectional view illustrating the relationship between the flow rate of a solder jet and the temperature detected by an infrared camera. 11 is a thermal image and a graph illustrating an example of a temperature distribution of a primary jet in a normal state. 11 is a thermal image and a graph illustrating an example of an abnormal temperature distribution of a primary jet. FIG. 13 is a conceptual diagram illustrating an example of monitoring a primary jet using an inspection frame. FIG. 13 is a conceptual diagram illustrating an example of monitoring a secondary jet using an inspection frame. 13 is a flowchart illustrating a method for evaluating a solder jet and a method for manufacturing a printed circuit board according to a fourth embodiment. 13 is a flowchart illustrating a method for evaluating a solder jet according to a modified example of the fourth embodiment.

The following describes in detail the embodiments of the present disclosure with reference to the drawings. Several embodiments are described below, but it is intended from the beginning of the application that the configurations described in each embodiment will be appropriately combined. In the following, the same or equivalent parts in the drawings are given the same reference numerals, and in principle, their description will not be repeated.

Embodiment 1.
FIG. 1 is a conceptual perspective view illustrating the configuration of a soldering apparatus to be evaluated by a solder jet evaluation apparatus according to the present embodiment.

Referring to FIG. 1, the soldering device 100 includes a housing 101, a molten solder bath 102 disposed inside the housing 101, a transport conveyor 104, a preheating device 106, and an infrared camera 107.

The molten solder bath 102 is equipped with a motor 108 that drives an impeller that causes the molten solder to flow. When the motor 108 causes the molten solder to flow, a solder jet is generated from the molten solder bath 102 toward the top.

The transport conveyor 104 transports the printed circuit board 103, which is shown as a representative example of an object to be soldered, inside the preheating device 106 and above the molten solder bath 102. The preheating device 106 includes a preheater 105. The preheater 105 heats the printed circuit board 103 prior to soldering in the molten solder bath 102. As the printed circuit board 103 passes above the molten solder bath 102 on the transport conveyor 104, it comes into contact with the solder jet, and the components at the contact points are soldered.

The infrared camera 107 is provided as one example of a "temperature distribution measuring device" that has the function of measuring or monitoring the temperature distribution within a specified field of view directed from above the molten solder bath 102 toward the transport conveyor 104 and the molten solder bath 102, including within an object passing over the molten solder bath 102.

Figure 2 is a conceptual perspective view illustrating the operation during an evaluation test of the solder jet according to this embodiment.

Referring to FIG. 2, during the solder jet evaluation test, in the soldering device 100 shown in FIG. 1, a solder jet evaluation device 200 is transported by the transport conveyor 104 instead of the printed circuit board 103.

2 shows the timing when the evaluation device 200 passes over the molten solder bath 102. At this timing, the solder jet 110 ejected from the molten solder bath 102 is partially in contact with the thin plate 201 of the evaluation device 200. At this timing, the thin plate 201 in contact with the solder jet 110 is photographed from above by the infrared camera 107, and an image showing the temperature distribution in the surface (planar direction) of the thin plate 201 (hereinafter also referred to as a "thermal image") is obtained. For example, the infrared camera 107 photographs multiple sheets in succession while the thin plate 201 is being transported at a predetermined constant speed. Furthermore, a display unit 109 for displaying the thermal image is provided. The display unit 109 is composed of a liquid crystal display or the like, and has a function of displaying information based on the image photographed by the infrared camera 107.

In this embodiment, the solder jet 110 is composed of a primary jet 111 and a secondary jet 112. The primary jet 111 has an uneven shape because it is jetted from a multi-hole jet port. In contrast, the secondary jet 112 has a uniform surface shape because it is jetted from a single large opening jet port.

In this embodiment, the state of the solder jet 110 is evaluated by image processing using a thermal image captured by the infrared camera 107. Note that it is also possible to realize the function of the "temperature distribution measuring instrument" using equipment other than the infrared camera 107, as long as it is possible to acquire a similar thermal image.

Figure 3 shows a block diagram illustrating an example of the configuration for image processing in the solder jet evaluation test according to this embodiment.

Referring to FIG. 3, thermal imaging data (e.g., data showing temperature measurement values for each of a plurality of pixels constituting the thermal image) constituting the thermal image captured by the infrared camera 107 is input to the controller 300. In addition, the thermal image captured by the infrared camera 107 can be directly displayed on the display unit 109 in a visible manner (e.g., in a manner in which the display color differs according to the detected temperature corresponding to each pixel).

The controller 300 can be configured, for example, as a function of a personal computer. Alternatively, although the controller 300 and the infrared camera 107 are depicted as separate devices in FIG. 3, the controller 300 can also be configured by a microcomputer or the like built into the infrared camera 107.

The controller 300 has an A/D (Analog to Digital) converter 310 and a D/A (Digital to Analog) converter 340 as an interface with the outside, a memory 320, a CPU (Central Processing Unit) 330, and a bus 350 as a data transmission path.

The A/D converter 310, memory 320, CPU 330, and D/A converter 340 can exchange data and signals with each other via bus 350. The memory 320 is configured to include a ROM (Read Only Memory) and a RAM (Random Access Memory), etc. For example, the memory 320 stores a program for executing the solder jet evaluation test according to this embodiment and data used by the program. Alternatively, the memory 320 can store calculated data (various parameter values, judgment results, processed image data, etc.) obtained as a result of the evaluation test.

The D/A converter 340 converts a digital signal indicating the calculation data calculated by the CPU 320 into an analog voltage signal and outputs it to the outside of the controller 300. As a result, the calculation data is supplied to an external device of the controller 300 as output data of the controller 300. For example, the display unit 109 can display various parameter values, judgment results, and images (including images after processing) obtained by the evaluation test of the solder jet 110 according to the output signal of the controller 300.

Next, a configuration example of the evaluation device 200 shown in FIG. 2 will be described with reference to FIGS. 4A to 4C.
4A shows a perspective view of the evaluation device 200 when it is assembled. The evaluation device 200 is constructed by attaching a thin plate member (hereinafter, simply referred to as a “thin plate”) 201 to a conveying member 210.

Figure 4B shows an exploded view of Figure 4A to explain an example configuration of the conveying member 210, and Figure 4C shows a plan view of the evaluation device 200 seen from above.

The conveying member 210 has an upper jig 211, a lower jig 212, a spacer 213, and a knurled screw 214, a positioning pin 215, and a hexagon socket bolt 216 as "fixing members."

The lower jig 212 has a rectangular shape, and the upper jig 211 has a so-called "U" shape with an opening on the rear side in the conveying direction on the conveyor 104. The thin plate 201 is attached to the first side 212a of the two opposing sides of the lower jig 212. That is, in the surface direction of the thin plate 201, a space 219 is provided between the thin plate 201 and the second side 212b of the two sides. The first side 212a is conveyed in the conveying direction ahead of the second side 212b on the conveyor 104.

The positional relationship between the upper jig 211 and the lower jig 212 and the spacer 213 is determined by two positioning pins 215. The thin plate 201 is placed in the space formed by the spacer 213 between the upper jig 211 and the lower jig 212. The thin plate 201 is fixed to the lower jig 212 (first side 212a) by one knurled screw 214. Furthermore, the upper jig 211, the lower jig 212, and the spacer 213 are fastened together by nine hexagon socket bolts 216 without the thin plate 201 being interposed.

The thickness of the spacer 213 is greater than the thickness of the thin plate 201, and the thin plate 201 is fixed to the lower jig 212 while being arranged so that there is a gap (corresponding to the "first gap") between the spacer 213 and the upper jig 211 in the thickness direction of the thin plate 201 to allow for thermal expansion of the thin plate 201.

Furthermore, as shown in FIG. 4C, the thin plate 201 is arranged in a positional relationship with respect to the spacer 213 such that there is a gap 217 between the thin plate 201 and the spacer 213 even in the in-plane direction of the thin plate 201. That is, the thin plate 201 is placed on the lower jig 212 in a positional relationship such that there is a gap 217 between the thin plate 201 and the spacer 213, and is fixed to the lower jig 212 (first side 212a) by a knurled screw 214 that passes through the upper jig 211.

The length (in the plane direction) of the gap 217 is designed to be greater than (linear expansion coefficient of the thin plate 201) x (temperature difference between the room and the solder jet 101) x (width of the thin plate 201). This prevents the thin plate 201 from warping, as it is restrained by the spacer 213, even if the thin plate 201 thermally expands when it comes into contact with the solder jet 110. The gap 217 corresponds to the "second gap."

On the other hand, in order to prevent deformation of the thin plate 201 due to thermal expansion, the conveying member 210 is structured to support the thin plate 201 only at its periphery, which raises concerns about the thin plate 201 bending due to its own weight. For this reason, it is preferable to select a highly rigid material (e.g., tungsten) for the thin plate 201 to reduce the effects of bending due to its own weight.

By constructing the evaluation device 200 in this manner, the thin plate 201 is restrained only at the point where the knurled screw 214 is tightened, so that the thin plate 201 is not restrained from expanding or contracting due to thermal expansion when it comes into contact with the solder jet 110. As a result, when it comes into contact with the solder jet 110, the thin plate 201 can maintain a flat state without warping. As a result, the temperature distribution within the surface of the thin plate 201 on the thermal image captured by the infrared camera 107 can be obtained with high reproducibility as an accurate reflection of the contact area between the thin plate 201 and the solder jet 110.

The thin plate 201 is preferably made of a material with high thermal conductivity, and can be made of a tungsten plate with a thickness of 0.2 mm and dimensions of 200 mm width x 200 mm length. The surface of the thin plate 201 (tungsten plate) photographed by the infrared camera 107 is preferably sprayed with a black body spray to increase the emissivity of that surface. The thin plate 201 is made of dimensions and materials such that, when it comes into contact with the solder jet 110, the rate of heat transfer by thermal conduction inside the thin plate 201 is higher than the rate of heat transfer by heat transfer from the solder jet 110 to the thin plate 201.

The thickness and material of the thin plate 201 can be selected based on the Biot number. The Biot number is generally used as a parameter that indicates the speed of heat transfer in thermal conduction. Since the thickness of the thin plate 201 is significantly smaller than the surface size (0.2<<200), in this embodiment, the Biot number can be calculated as follows: (Biot number) = (heat transfer coefficient of solder jet 110) x (plate thickness) ÷ (thermal conductivity of thin plate 201).

If the Biot number is greater than 0.1, this means that the transfer of heat by internal thermal conduction tends to be slower than the transfer of heat by thermal conduction of the solder jet 110. In this case, there will be a time delay before the state of the solder jet 110 appears as a temperature distribution on the surface of the thin plate 201 photographed by the infrared camera 107. Therefore, in this embodiment, it is preferable to select the material and thickness of the thin plate 201 so that the Biot number is 0.1 or less.

Figure 5 shows an example of a graph showing the relationship between the Biot number and the material and thickness of a thin plate, in which the Biot number was calculated for a tungsten plate and a titanium plate, with the plate thickness used as a parameter.

The horizontal and vertical axes of Fig. 5 indicate the plate thickness and Biot number, respectively. Fig. 5 shows characteristic C1 when the thin plate 201 is a titanium plate, and characteristic C2 when it is a tungsten plate. The thermal conductivity of tungsten is 174 [W/m/K], and the thermal conductivity of titanium is 21.9 [W/m/K]. On the other hand, the thermal conductivity of the solder jet 110 is 10,000 [W/ ^m2 /K].

From Figure 5, it can be seen that with a tungsten plate (C2), the Biot number does not reach 0.1 even when the plate thickness is 1 mm. On the other hand, with a titanium plate (C1), the Biot number exceeds 0.1 when the plate thickness exceeds 0.2 mm. Therefore, when the thin plate 201 is made of a titanium plate, the plate thickness should be selected to be 0.2 mm or less.

By making such a selection based on the Biot number, it is possible to use metals other than tungsten and titanium (e.g., aluminum, iron, etc.) as the material for the thin plate 201. Alternatively, the thin plate 201 can be made of ceramics such as aluminum nitride and silicon nitride.

A hole with a diameter of 4 mm is drilled in the thin plate 201 (e.g., a tungsten plate). A knurled screw 214 with a diameter of 3 mm is passed through the hole and fixed to the lower jig 212, so that the thin plate 201 is connected to the conveying member 210 in a link-like manner without being in close contact. The diameter of the hole in the thin plate 201 is designed to be larger than the diameter of the knurled screw 214. The difference in diameter between the two is designed so that the gap between the hole and the knurled screw 214 does not hinder the thermal expansion of the thin plate 201 when it comes into contact with the solder jet 110. Specifically, the size of the gap is determined so that the thin plate 201 is not deformed by the thermal expansion of the knurled screw 214 in the planar direction.

In the example of Figures 4A to 4C, only one hole is drilled in the thin plate 201, but if a gap is secured between the fixing knurled screw 214 and the hole in the thin plate (tungsten plate) 201 that can absorb the amount of expansion and contraction due to thermal expansion, multiple holes may be provided in the thin plate (tungsten plate) 201, and the thin plate 201 may be linked to the conveying member 210 at multiple points using the knurled screw 214.

On the other hand, the upper jig 211, the lower jig 212, and the spacer 213 can be manufactured by processing a heat-resistant resin in which glass cloth is impregnated with epoxy resin. Alternatively, the upper jig 211, the lower jig 212, and the spacer 213 can be made of heat-resistant resins such as polyether, ether, ketone-based resins, and polyimide-based resins, metals such as aluminum and stainless steel, or ceramics such as aluminum oxide, aluminum nitride, and silicon nitride.

The space 219 between the thin plate 201 and the second edge 212b of the lower jig 212, located on the rear side of the thin plate 201 in the transport direction, is required to prevent the shape of the solder jet 110 from being obstructed.

Figures 6A and 6B show conceptual cross-sectional views of a thin plate 201 in contact with a solder jet 110. Figures 6A and 6B show cross-sectional views including the VI-VI section of the evaluation device 200 shown in Figure 4A.

Figure 6A shows a cross-sectional view of the conveying member 210 in a contact state where the space 219 is provided and the shape of the solder jet 110 is not obstructed. On the other hand, Figure 6B shows a cross-sectional view of the conveying member 210 in a contact state where the space 219 is not provided and the shape of the solder jet 110 is obstructed.

Referring to Figures 6A and 6B, the lower jig 212 protrudes from the thin plate 201 in the direction (downward) from the thin plate 201 toward the solder jet 110. For this reason, in a structure in which the thin plate 201 is attached to the transport member 210 without providing a space 219 as in Figure 6B, the shape of the solder jet 110 is disturbed when the thin plate 201 and the solder jet 110 come into contact with each other, i.e., when a thermal image is taken. This raises concerns that it may be difficult to obtain a thermal image that accurately reflects the shape of the solder jet 110.

In response to this, as shown in FIG. 6A, by appropriately ensuring the length W1 of the space 219 along the transport direction relative to the length WS of the nozzle of the solder jet 110 along the transport direction, the shape of the solder jet 110 is not disturbed while the thin plate 201 is in contact with the solder jet 110. As a result, it becomes possible for the infrared camera 107 to acquire a thermal image that accurately reflects the shape of the solder jet 110.

For example, if a space 219 is provided between W1 and WS so that W1>(WS/2) holds, it is possible to avoid distortion of the shape of the solder jet 110 and obtain a thermal image of the thin plate 201. Note that the above WS can be set in accordance with the width of the solder jet 110 (e.g., the width of the secondary jet 112) that is generated when the motor 108 of the molten solder bath 102 is driven at maximum output in the soldering device 100.

6A and 6B also show the mounting structure of the thin plate 201 to the upper jig 211, the lower jig 212, and the spacer 213 using the knurled screw 214 and the bolt 216, as described in FIGS. 4A to 4C. That is, the thin plate 201 is fixed to both the upper jig 211 and the lower jig 212 without being in close contact with them due to the presence of the spacer 213, and a gap 218 is provided between the thin plate 201 and the upper jig 211 in the plate thickness direction. Also, a gap 221 is provided between the knurled screw 214 and the hole in the thin plate 201 through which the knurled screw 214 passes due to the difference in diameter between the two. The gap 218 corresponds to an example of the "first gap", and the gap 221 corresponds to an example of the "third gap". In this way, the thin plate 201 is fixed with gaps in both the thickness direction and the surface direction, so the thin plate 201 can come into contact with the solder jet 110 while maintaining a flat surface without being deformed by thermal expansion.

In Figures 4A to 4C, an example of the configuration of the conveying member 210 in which the lower jig 212 is shaped like the letter "R", is described, but the configuration of the conveying member 210 is not limited to this example.

7 and 8 show modified configurations of the conveying member 210. FIG.
7, in the first modified example, the lower jig 212 of the transport member 210 has a so-called "U" shape with an opening on the rear side in the transport direction, similar to the upper jig 211. In this way, it is possible to transport the evaluation device 200 while avoiding the disturbance of the shape of the solder jet 110 without providing the space 219 described in FIG. 6A. This also makes it possible to reduce the size of the evaluation device 200. On the other hand, in the structure of FIG. 7, the structural strength of the lower jig 212 is reduced compared to the "U" shape of FIGS. 4A to 4C.

Referring to FIG. 8, in the second modified example, the conveying member 210, which is configured in a U-shape like the first modified example, further includes a reinforcing member 220 that is a separate member from the upper jig 211 and the lower jig 212. The lower jig 212 is created so as to have a portion 212c that is longer than the upper jig 211 on the rear side in the conveying direction, i.e., on the opening side. Furthermore, the reinforcing member 220 is fixed by bolts 222 to the portions 212c on both sides that face each other in a direction that intersects the conveying direction.

In the structure of FIG. 8, the reinforcing material 220 is located above the thin plate 201 with respect to the outlet of the solder jet 110, so the shape of the solder jet 110 that contacts the thin plate 201 is not disturbed by the reinforcing material 220. Therefore, it is possible to perform an evaluation test using the evaluation device 200 without providing a space 219 and avoid disturbance of the shape of the solder jet 110. Also, compared to FIG. 7, the structural strength of the transport member 210 can be ensured. In FIG. 8, the lower jig 212 corresponds to an example of the "first member", and the reinforcing material 220 corresponds to an example of the "second member".

Next, an evaluation test using the solder jet evaluation device according to embodiment 1 will be described with reference to Figures 9A to 9C.

Figure 9A shows a conceptual perspective view of the evaluation device 200 passing above the solder jet 110. In this state, the solder jet 110, including the primary jet 111 and the secondary jet 112, partially contacts the underside of the thin plate 201.

In FIG. 9B, the contact state of the primary jet 111 and secondary jet 112 with the thin plate 201 in the state of FIG. 9A is conceptually shown by indicating the evaluation device 200 with a dotted line. In the thin plate 201, the temperature rises at the contact area with the solder jet 110 (primary jet 111 and secondary jet 112), which is hatched in FIG. 9B.

Therefore, by photographing the thin plate 201 in the state shown in Figure 9A with the infrared camera 107, a thermal image can be obtained that reflects the temperature rise in the blackened area shown in Figure 9B.

FIG. 9C shows a conceptual diagram illustrating the temperature distribution in the thermal image 250 using isothermal lines.
9C , in the thermal image 250, the portion of the thin plate 201 in contact with the solder jet 110 becomes hot. The isothermal line 111t shows a spotted temperature distribution corresponding to the contact portion with the primary jet 111. The isothermal line 112t shows a band-like temperature distribution corresponding to the contact portion with the secondary jet 112. That is, the isothermal lines 111t and 112t show the shapes of the primary jet 111 and the secondary jet 112 at the contact portion with the thin plate 201. That is, the states of the primary jet 111 and the secondary jet 112 can be evaluated based on the isothermal lines 111t and 112t.

For example, the thermal image 250 is divided into M x N pixel regions (M, N: natural numbers) so that the temperature on the surface of the thin plate 201 can be processed in association with coordinates. That is, the thermal image 250 is divided into M horizontal (width) regions (e.g., M = 640) and N vertical (transport) regions (e.g., N = 480), resulting in a two-dimensional matrix having 640 x 480 pixel regions.

As a result, the contact points with the solder jet 110, i.e., the primary jet 111 and secondary jet 112, as shown in FIG. 9C, can be identified from the temperature data in each of the multiple pixel regions in the thermal image 250. That is, by image processing of the thermal image 250, the shape of the cut surface of the solder jet 110 by the evaluation device 200 (thin plate 201) can be detected. As a result, the state of the solder jet 110 (primary jet 111 and secondary jet 112) can be grasped, and it can be stably evaluated whether or not it is in a state where a printed circuit board can be normally manufactured.

Embodiment 2.
In the second embodiment, an example of determining whether a solder jet is good or bad in an actual soldering apparatus 100 will be described.

In the soldering device 100 shown in FIG. 1, for example, in a molten solder bath 102 from which a solder jet 110 of lead-free solder (e.g., standard composition of Sn-3.0Ag-0.5Cu) is ejected, the temperature of the solder jet 110 is controlled to a target temperature (e.g., 250°C) by a solder heater (not shown).

In this state, the solder jet evaluation device 200 described in the first embodiment is passed above the molten solder bath 102, and when the solder jet 110 and the evaluation device 200 (thin plate 201) are in contact, the infrared camera 107 captures an image of the evaluation device 200 (thin plate 201). This results in the thermal image 250 shown in FIG. 9C.

FIG. 10 shows an example of image processing of a thermal image 250 .
10, as an example of image processing, a binarization process is performed with a threshold value of 240° C. for the temperature of solder jet 110 of 250° C. described above, and a processed image 252 is obtained in which areas at 240° C. or higher and areas below 240° C. are identified. Areas at 240° C. or higher are indicated by hatching in FIG. 10. Processed image 252 allows classification of each of the above-mentioned multiple pixel areas (e.g., 640×480 pixels) into areas at 240° C. or higher, i.e., areas in contact with solder jet 110, and areas below 240° C., i.e., areas not in contact with solder jet 110.

In the example image of FIG. 10, the contact area with the primary jet 111 gradually shrinks toward the top of the image because, as shown in FIG. 1, the transport conveyor 104 is inclined at a certain angle (e.g., about 5°) with respect to the horizontal plane.

In the processed image of FIG. 10, an inspection frame as shown in FIG. 11 is defined in advance.
11, an inspection frame 111c for the primary jet 111 and an inspection frame 112c for the secondary jet 112 can be provided in accordance with the jet shape of the solder jet 110 (primary jet 111 and secondary jet 112). Each of the inspection frames 111c and 112c can be defined in units of a plurality of pixel regions (e.g., 640×480 pixels) as described in FIG. 9C.

In each inspection frame 111c and inspection frame 112c, the contact area (hatched area) with the solder jet 110 and the non-contact area (white area) are distinguished by pixel area. As a result, for example, in each inspection frame 111c, the quality of the state of the primary jet 111 can be determined based on the area of the contact area with the solder jet 110 (the number of pixel areas) relative to the total area (the number of pixel areas). For example, when the ratio of the contact area to the total area is equal to or greater than a predetermined judgment value (e.g., 40 [%]), the state of the primary jet 111 corresponding to the inspection frame 111c is determined to be good (passed), while when the ratio is less than the judgment value, the state of the primary jet 111 can be determined to be poor (failed).

The state of the secondary jet 112 can be determined by introducing a quantitative value as described in Figure 12.

Referring to FIG. 12, in the inspection frame 112c of the secondary jet 112, the contact length can be calculated by counting the number of pixels in the contact area (hatched area) at each of multiple locations along the vertical direction of the screen (i.e., the line transport direction).

For example, in each inspection frame 112c, contact lengths L1 to L5 can be calculated at five locations. The average of contact lengths L1 to L5 can then be taken as the contact length of the secondary jet 112 in that inspection frame 112c. By determining whether the contact length (average value) is within a predetermined normal range (for example, 50% to 80% of the vertical length of the inspection frame 112c), it is possible to evaluate whether the condition of the secondary jet 112 is good (pass) or bad (fail).

In addition, by comparing the contact width between the multiple inspection frames 112c provided for the secondary jet 112, it is also possible to evaluate the variation (fluctuation) in the jet state along the direction perpendicular to the line conveying direction of the secondary jet 112 (width direction).

For example, in the example of FIG. 12, the contact lengths (average values) LAV1 to LAV5 of the solder jet (secondary jet 112) are calculated for each of the five inspection frames 112c provided, and then the maximum value LAVmax of LAV1 to LAV5 is calculated relative to the average value LAV* (overall average value) of LAV1 to LAV5, allowing the variation in the width direction of the secondary jet 112 to be evaluated. For example, if (LAV*/LAVmax) is equal to or greater than a predetermined judgment value (e.g., 80[%]), it can be judged that the variation in width of the solder jet 110 (secondary jet 112) is small and in a good condition.

As explained in the second embodiment, the thermal image obtained by photographing with the evaluation device of the first embodiment can be used to quantitatively determine the state (good/bad) of the solder jets 110 (primary jets 111 and secondary jets 112) through image processing that distinguishes between contact and non-contact with the solder jets 110 for each pixel area.

FIG. 13 shows an example of a defect determination based on a thermal image.
13, for the primary jet 111, the ratio of the contact area with the solder jet 110 in the inspection frames 111x, 111y, and 111z is lower than the judgment value, so that a defect is automatically detected. Also, from the position of the inspection frame 111c judged to be defective, the non-contact area or the area with insufficient contact of the primary jet 111 can be grasped. Similarly, for the secondary jet 112, the variation in the contact length with the solder jet 110 between the multiple inspection frames 112c is large, so that the secondary jet 112x having an uneven shape in the width direction can be grasped. As a result, an abnormality such as a blockage of the flow path of the solder jet 110, an inclination of the nozzle of the solder jet 110, or an insufficient flow rate of the solder jet 110 can be easily detected.

In this way, according to the second embodiment, the state of the solder jet 110 can be confirmed and evaluated using the solder jet evaluation device 200 before the start of the manufacturing process (mass production) of the printed circuit board 103 by the soldering device 100 or during the manufacturing process.

According to the second embodiment, if the condition of the solder jet 110 is determined to be defective by the quantitative evaluation described above, it is possible to estimate the cause of the defect from the actual thermal image.

In the second embodiment, inspection frames 111c and 112c are provided for the primary jet 111 and the secondary jet 112, respectively, and pass/fail judgment is performed based on the number of contact areas in each inspection frame 111c and 112c. However, pass/fail judgment is also possible without providing such an inspection frame.

For example, a reference thermal image of the solder jet 110 when it is good can be defined in advance for the processed image 252 in FIG. 10. In the reference thermal image, whether each of the multiple image regions (e.g., 640×480) defined in common with the processed image 252 (FIG. 10) is a contact region or a non-contact region is set in advance. Therefore, a quantitative determination of the quality of the solder jet 110 can be realized similar to that described above by comparing the match rate (number of matching pixel regions/total number of pixel regions) by pattern matching, which determines whether each of multiple pixel regions is a contact region or a non-contact region, between the processed image 252 (FIG. 10) obtained from the thermal image 250 and the reference region, with a determination value. The reference thermal image can be obtained in advance by an actual experiment in which a thermal image of the evaluation device 200 of the solder jet is taken in a soldering device 100 that is determined to be normal.

Furthermore, by outputting an abnormality detection signal in response to the occurrence of a defective state detected according to the second embodiment, it is possible to notify the manager and worker of the abnormality by an alarm and/or a screen display, etc. Through re-inspection and re-maintenance of the soldering device 100 in response to the abnormality notification, the solder jet 110 can be returned to a normal state, and then the printed circuit board 103 can be soldered.

The abnormality detection signal can also be sent to a control unit (not shown) of the soldering device 100 to control the transport conveyor 104 to automatically stop. This makes it possible to avoid soldering being continued for a long period of time while the solder jet 110 is in an abnormal state, thereby reducing the rate of soldering defects on the printed circuit board 103.

Embodiment 3.
In embodiment 3, a further description will be given of an evaluation method using the solder jet evaluation device according to embodiment 1. In embodiment 3, the method goes beyond automatic detection of defective states of solder jets using thermal images to automatically detect the causes of the defects.

First, we will explain typical examples of causes of abnormal occurrence of solder jet 110 using Figures 14 to 18.

Figure 14 shows a perspective view of the soldering device 100 that is the subject of anomaly detection in embodiment 3. The content of Figure 14 is the same as that of Figure 2, and the evaluation method for the solder jet according to embodiment 3 is executed by having the infrared camera 107 acquire a thermal image when the evaluation device 200 described in embodiment 1 passes above the molten solder bath 102 that is in a state of spraying the solder jet 110.

Figure 15 shows a cross-sectional view of the solder jet 110 taken along line XV-XV in Figure 14 when the solder jet 110 is normal. Meanwhile, Figures 16 to 18 show cross-sectional views taken at the same position as Figure 15 to explain typical causes of abnormalities in the solder jet 110.

Figure 15 shows the normal state of the solder jet 110, with the dotted lines in the figure indicating the flow of solder. The solder inside the molten solder bath 102 is heated by a solder heater 121, and is sucked into the flow path by the rotation of the impeller 124 driven by the motor 108. The solder sucked into the impeller 124 is ejected from the nozzle 123, forming the solder jet 110. Under normal conditions, in the width direction (i.e., within the XV-XV cross section), the surface of the solder at the nozzle 123 and the transport surface by the transport conveyor 104 are horizontal.

In contrast, the following five are typical causes of abnormalities in the solder jet 110:

(1) Occurrence of clogging in the flow path of the solder jet 110 (FIG. 16)
(2) Inclination of the solder nozzle 123 (FIG. 17)
(3) Inclination of the conveying surface caused by the conveyor 104 (FIG. 18)
16, foreign matter 122 is generated due to dross, which is an oxide of solder, or due to flux residue, and clogging caused by the foreign matter 122 causes abnormalities in the solder jet 110 (Cause 1). In this case, it is necessary to take measures to remove the clogging caused by the foreign matter 122 by cleaning (Measure 1).
17 , insufficient position adjustment of nozzle 123 of solder jet 110, or tilt of nozzle 123 caused by incorrect position adjustment, causes an abnormality in solder jet 110 (Cause 2). In this case, it is necessary to measure the position of the nozzle of solder jet 110 with a vernier caliper or the like, and adjust the position of the nozzle of solder jet 110 by operating height adjustment bolt 125, thereby returning nozzle 123 to the horizontal (Countermeasure 2).

Referring to FIG. 18, if tilting of the conveying surface occurs due to height differences or distortion between opposing conveyors 104, even if the ejected solder jet 110 is normal, there is a risk that the shape of the solder jet 110 will be abnormal when it comes into contact with the conveying surface evaluation device 200 or the printed circuit board 103. Therefore, tilting of the conveying surface caused by the conveyor 104 can also cause abnormalities in the solder jet 110 (Cause 3). In this case, adjustment is required to make the height of the conveyor 104 uniform (Measure 3).

Still another cause of the abnormality in the solder jet 110 is insufficient flow rate of the solder due to insufficient output adjustment, incorrect output setting, or damage to the motor 108 that drives the impeller 124 to move the solder jet 110 (Cause 4). In this case, adjustment of the output of the motor 108 or maintenance is required (Countermeasure 4).

Alternatively, insufficient temperature of the solder due to insufficient adjustment, incorrect setting, or damage to the temperature regulator (not shown) of the heater 121 for heating the solder may also cause an abnormality in the solder jet 110 (Cause 5). In this case, adjustment or maintenance of the temperature regulator of the heater 121 for heating is required (Countermeasure 5).
As described above, there are multiple causes of defects in solder jet 110, and the measures to be taken vary depending on the cause. Therefore, when a defect is detected in the evaluation test of solder jet 110 based on the thermal image captured by evaluation device 200 (thin plate 201) as described in the second embodiment, it is preferable to estimate the cause of the abnormality and provide "adjustment guidance" that guides adjustment items as a countermeasure.

Figure 19 is a flowchart explaining the method for evaluating solder jets and the method for manufacturing printed circuit boards according to embodiment 3.

Referring to FIG. 19, the manufacturing process of the printed circuit board according to this embodiment includes a solder jet evaluation process P100 and a soldering process P200. The solder jet evaluation process P100 includes steps S100 to S180 for executing the solder jet evaluation method according to this embodiment. The processing of steps S100 to S180 is performed, for example, by the controller 300 (FIG. 3).

Referring to FIG. 19, in step S100, the controller 300 acquires thermal imaging data captured by the infrared camera 107 when the thin plate 201 of the evaluation device 200 described in embodiment 1 is in contact with the solder jet 110 above the molten solder bath 102.

The controller 300 calculates evaluation parameter values indicating the feature quantities of the captured thermal image in S110. For example, the evaluation parameter values include numerical data indicating the absolute value of the temperature, the density of the isotherms, the shape of the isotherms, and the amount of change in the isotherms relative to the temperature distribution determined to be normal. Specifically, in an arbitrary region of the thermal image, the average temperature, the maximum temperature, the temperature gradient, the value obtained by dividing the area of the isotherm of an arbitrary temperature by its perimeter, the number of isothermal regions equal to or higher than an arbitrary temperature, the difference value between the temperature distribution in the captured thermal image and the temperature distribution previously determined to be normal, and the like can be used as the evaluation parameter values. In addition, the above feature quantities may be used as evaluation parameter values by synthesizing multiple parameters or extracting independent parameters using software for executing a principal component analysis method, which is a known technology, and software for executing an independent component analysis method.

The controller 300 executes a process of determining the quality of the state of the solder jet 110 based on the thermal image in S120. The quality determination process can be executed based on the surface area ratio of the contact area with the solder jet 110 within the inspection frames 111c, 112c shown in Figures 11 to 13 of the second embodiment. Alternatively, as explained in the second embodiment, the quality determination in S120 can also be executed by pattern matching between a predetermined reference thermal image and the processed image 252 of the thermal image (Figure 10).

The reference thermal image can be configured to specify the actual temperature distribution in addition to the contact and non-contact areas with the solder jet 110 for each pixel region. In this case, a pass/fail determination can be made by pattern matching the temperature distribution of the reference thermal image with the temperature distribution of the thermal image 250 using any known method.

Furthermore, in S120, a defect cause determination process for adjustment guidance is executed using the evaluation parameter values calculated in S110. The defect cause determination process is executed using past evaluation parameter values stored in database (DB) 360. As an example, the defect cause determination process can be executed by machine learning of the evaluation parameter values stored when the state of solder jet 110 was previously determined to be defective.

For example, defect cause determination can be performed by machine learning using a neural network, as shown in Figure 20.

Figure 20 is a conceptual diagram explaining a neural network used in an example of machine learning for defect cause determination processing.

Referring to FIG. 20, neural network 370 includes n neurons Ni1 to Nin (n: an integer of 2 or more) that constitute the input layer, m neurons No1 to Nom (m: a natural number of 2 or more) that constitute the output layer, and a plurality of neurons that constitute a hidden layer connected between the input layer and the output layer. The structure of neural network 370 can be set arbitrarily depending on the number of input layers, hidden layers, and output layers, and the number of neurons in each layer.

An activation function is input to each neuron represented by a circle symbol in FIG. 20. For example, a sigmoid function can be used as the activation function, but any known activation function can be applied. Furthermore, the weighting coefficients between each neuron can be determined by machine learning using multiple learning data obtained from past performance values, as described below.

The n neurons in the input layer are each input with a plurality (n) of evaluation data calculated in S110. On the other hand, the m neurons in the output layer are each associated in advance with a defect cause of the solder jet 110 (for example, each of the above-mentioned (Cause 1) to (Cause 5)).

The training data for the neural network 370 can be obtained by an experiment in which the soldering device 100 is intentionally created in a state in which the solder jet 110 is defective due to a specific cause. That is, an evaluation test is performed in which a thermal image of the evaluation device 200 is taken while creating such a specific cause of failure, and the evaluation parameter values obtained at this time are input to the neurons in the input layer. In the output layer, the value of the neuron corresponding to the specific cause of failure is set to "1", and the values of the other neurons are set to "0". By providing such values for the neurons in the input layer and output layer, a set of training data can be constructed.

By performing similar experiments and evaluation tests for each different cause of defects, it is possible to obtain training data that covers multiple causes of defects. In addition, by substituting the evaluation parameters obtained in the evaluation test when the solder jet 110 is in a normal state into the input layer and setting each neuron value in the output layer to "0", it is possible to obtain training data under normal conditions (when the solder jet 110 is in a good state).

In this way, the neural network 370 can be obtained by machine learning using training data obtained in advance from actual experiments with the soldering device 100 under normal and abnormal conditions. The structure of the neural network 370 and data indicating the weighting coefficients between each neuron can be stored in the database 360.

Referring again to FIG. 19, in S120, the controller 300 inputs the evaluation parameter values determined in S110 to each of the multiple (n) neurons constituting the input layer of the neural network 370 (FIG. 20). As a result, each of the multiple (m) neurons constituting the output layer outputs a value in the range of 0 to 1.0 representing the predicted probability of occurrence of the defect cause associated with the neuron.

Therefore, if the condition of the solder jet 110 is judged to be defective in the above-mentioned pass/fail judgment, a defect cause judgment process can be executed to extract the defect cause that is currently assumed to be occurring from multiple predetermined causes based on the output values of each neuron in the above-mentioned output layer. The controller 300 outputs the results of the pass/fail judgment process and the defect cause judgment process in S120 in S130.

When the controller 300 determines that the condition of the solder jet 110 is good (YES in S170), it ends the solder jet evaluation process P100. At this time, the controller 300 can output guidance using the display unit 109 to the effect that the condition of the solder jet 110 is good and that mass production of the printed circuit board 103 can be started by the soldering process P200 using the soldering device 100 as is.

As a result, in a soldering device 100 where the solder jet 110 is in good condition, the printed circuit board soldering process P200 is executed by passing the printed circuit board 103 sequentially over the molten solder bath 102 using the transport conveyor 104.

On the other hand, if the condition of the solder jet 110 is determined to be defective (NO in S170), the controller 300 outputs adjustment guidance on the display unit 109 in S180 and ends the solder jet evaluation process P100. In S180, the defect cause with a high probability of occurrence is extracted by the defect cause determination process in S120, and guidance is output to notify measures for the extracted defect cause. For example, from a number of messages for notifying each of (Measures 1) to (Measures 5) that are predetermined to correspond to each of the above-mentioned (Cause 1) to (Cause 5), a message corresponding to the extracted defect cause can be selectively output as adjustment guidance.

Alternatively, in S180, if it is necessary to adjust the output of the drive system that drives the solder jet 110 or the solder temperature of the molten solder bath 102 in conjunction with the estimation result, it is also possible to automatically adjust the output of the motor 108 or the heater 121 for heating the solder.

After the adjustment guidance is output, the worker can adjust or maintain the soldering device 100 according to the guidance, and then mass production can begin using the soldering process P200. Alternatively, the flow chart in FIG. 19 can be temporarily terminated without proceeding to the soldering process P200 in order to reevaluate the state of the solder jet 110 after the inspection or maintenance. In this case, the process related to the flow chart in FIG. 19 will be executed again.

The controller 300 can add the evaluation parameter values calculated in S110 as training data for machine learning each time the solder jet evaluation process P100 is performed. That is, machine learning can be performed continuously even when the soldering device 100 is actually used (after going online). For example, the controller 300 evaluates and confirms the results of the pass/fail judgment and defect cause judgment process output by S130 in S150 and S160, and converts them into training data. As described above, if the result is "good (S170 is YES)," the evaluation parameter values calculated in S120 are set as the values of the neurons in the input layer, and the values of each neuron in the output layer are set to 0, thereby creating training data.

On the other hand, if it is judged to be "defective (S170 is NO)," training data can be created by determining the value of the neurons in the output layer to reflect the cause of the defect identified through adjustment or maintenance of the soldering device 100 based on the adjustment guidance, etc.

The created training data is added and stored in the database 360. By adding the additional training data and re-running the machine learning, the neural network 370 used for the judgment in S120 can be updated using data from actual use of the soldering device 100.

Alternatively, in S130, it is possible to output time-series regression prediction information to grasp the tendency of the condition of the solder jet 110 becoming abnormal, regardless of the pass/fail judgment result, i.e., even if the solder jet 110 is judged to be in a good condition.

FIG. 21 shows a conceptual diagram illustrating an example of regression prediction.
21, the evaluation parameter values (i.e., temperature distribution feature quantities) calculated in S120 are stored in a database (DB) 360, and can be plotted as time-series data against a time axis. Therefore, a regression line 380 of the time-series change of each evaluation parameter value can be obtained by known statistical processing.

As a result, as shown in FIG. 21, even when an upper and lower limit are set for any of the evaluation parameter values for management, the tendency for the evaluation parameter value to rise or fall before reaching the upper or lower limit can be detected from the slope of the regression line 380, etc. As a result, even when the condition of the solder jet 110 is determined to be good, it is possible to grasp in advance the tendency for the solder jet 110 to gradually become abnormal. This allows equipment cleaning or maintenance to be carried out efficiently.

In this way, according to the third embodiment, by performing a solder jet evaluation test using the solder jet evaluation device 200 described in the first embodiment, the state of the solder jet can be stably determined using thermal images. Furthermore, after confirming that the state of the solder jet 110 is good, a manufacturing process can be realized in which the printed circuit board 103 is continuously soldered, thereby suppressing the occurrence of defective products.

In addition, if the condition of the solder jet 110 is determined to be defective, the cause of the defect can be estimated by machine learning of the accumulated heat distribution features (evaluation parameter values) on the thermal images obtained in the solder jet evaluation test. Furthermore, it is also possible to automatically output guidance for dealing with the estimated cause of the abnormality.

Furthermore, by performing an evaluation test of the solder jet 110 using the evaluation device 200 each time the soldering device 100 is used, a database is constructed that sequentially accumulates information related to the thermal images and the judgment results, and this information is reflected in machine learning, thereby improving the accuracy of estimating the cause of the abnormality.

Embodiment 4.
In the first to third embodiments, the state of the solder jet 110 is evaluated using a thermal image of the contact surface between the solder jet 110 and a thin plate 201 simulating an object to be soldered (printed circuit board 103). On the other hand, in evaluating the state of the solder jet 110, it is also important to evaluate the shape of the vertical cross section of the solder jet 110.

Figures 22A to 22C show examples of the shape of the secondary jet 112 of the solder jet 110 in a vertical cross section (hereinafter also referred to as the first vertical cross section) along the transport direction of the transport conveyor 104.

As shown in Figures 22A to 22C, the shape of the solder jet in the first vertical cross section varies depending on the angle of the nozzle 126 that forms the jet outlet 123 and the position of the backplate 127 that is located at the end of the nozzle 126.

For example, by rotating the nozzle 126 as shown in FIG. 22B or by raising the back plate 127 as shown in FIG. 22C, the shape of the secondary jet 112 in the first vertical cross section (hereinafter also simply referred to as the "cross-sectional shape") on the downstream side in the conveyor transport direction can be changed from the state shown in FIG. 22A.

Next, the effect of the cross-sectional shape of the solder jet on soldering will be described.
Fig. 23A shows the cross-sectional shape of the solder jet (secondary jet 112) when the printed circuit board 103 has not passed. In contrast, Fig. 23B shows the contact state between the solder jet (secondary jet 112) having the cross-sectional shape shown in Fig. 23A and the printed circuit board 103 when the printed circuit board 103 has passed.

Figure 23B shows the contact length L between the solder jet (secondary jet 112) and the printed circuit board 103 along the transport direction, as described in embodiment 2 (Figure 12). Even if the contact length L is the same, if the contact angle between the two is different, it will affect the quality of the soldering. The contact angle can be evaluated using the departure angle θwd shown in Figure 23B as a parameter.

The separation angle θwd is defined as the angle between the printed circuit board 103 and the contour surface (top surface) of the solder jet (secondary jet 112) at the end along the transport direction of the contact area between the printed circuit board 103 and the solder jet (secondary jet 112) in the first vertical cross section described above.

Figure 24A shows the cross-sectional shape of the solder jet (secondary jet 112) when the back plate 127 is raised with respect to Figure 23A. Furthermore, Figure 24B shows the contact state between the solder jet (secondary jet 112) of the cross-sectional shape shown in Figure 24A and the printed circuit board 103 when the printed circuit board 103 passes.

As can be seen from a comparison of Figures 23B and 24B, the separation angle θwd of the printed circuit board 103 can be changed by changing the cross-sectional shape of the solder jet 110 through the operation of the backplate 127.

As a general trend, when the separation angle θwd is large, there is an advantage in that a larger amount of solder can be attached to the printed circuit board 103, but there is a possibility that a disadvantage is that short-circuit defects are more likely to occur in components with narrow electrode spacing. In contrast, when the separation angle θwd is small, the advantages and disadvantages are reversed from when the separation angle θwd is large.

Therefore, the separation angle θwd is optimized by adjusting the cross-sectional shape of the solder jet in accordance with the specifications of the printed circuit board 103 to be soldered. For example, when soldering a printed circuit board 103 that has many components to be inserted into the through holes, the separation angle θwd is increased to ensure the amount of solder that adheres to the through-hole electrodes, thereby ensuring soldering quality. On the other hand, when soldering a printed circuit board 103 that has many components with narrow electrode spacing, such as QFPs (Quad Flat Packages) or connectors, the separation angle θwd is reduced to prevent short circuit defects between electrodes.

The cross-sectional shape of the solder jet can be controlled by adjusting the position of the back plate 127 as described in Figures 23A and 24A, as well as by adjusting the shape and angle of the nozzle 126 or the rotation speed of the motor 108. In the evaluation of the solder jet described in embodiments 1 to 3, the thin plate 201 is used to monitor the change in shape of the solder jet within the contact surface between the printed circuit board 103 and the solder jet, for example, by using the contact length, but it is difficult to evaluate the cross-sectional shape of the solder jet, which affects the above-mentioned separation angle θwd, etc.

Therefore, in the fourth embodiment, we will explain a method for evaluating a solder jet based on the shape of the vertical cross section of the solder jet.

Referring again to FIG. 2, in the fourth embodiment, the evaluation device 200 uses an infrared camera 107 to directly photograph the solder jet 110 without the evaluation device 200 (thin plate 201) being present, thereby photographing a thermal image of the solder jet itself in a horizontal plane. Hereinafter, the thermal image of the solder jet 110 will be given the reference number 400 to distinguish it from the thermal image 250 of the thin plate 201 described in the first to third embodiments. Note that the thermal image 250 and the thermal image 400 may be photographed by a common infrared camera 107, or may be photographed by infrared cameras 107 arranged separately.

25A and 25B show examples of the thermal image and cross-sectional shape (first vertical cross section along the transport direction) of the solder jet. FIG. 25A shows an example of a thermal image 400 in which the cross-sectional shape of the solder jet has a large change in slope, while FIG. 25B shows an example of a thermal image 400 in which the cross-sectional shape of the solder jet has a small change in slope.

In the following drawings of this application, thermal images 400 are shown as color images displayed in grayscale. For this reason, each thermal image 400 shows shades of light and dark that correspond to the temperature difference between adjacent regions, but points of the same brightness in the same image do not necessarily mean that they are at the same temperature.

The solder jet ejected from the nozzle 123 is mirror-like and has a low emissivity, so the temperature of the solder jet measured by the infrared camera 107 is lower than the actual temperature of the solder jet. Furthermore, the infrared camera 107 measures the temperature of the liquid surface of the solder that has flowed out of the nozzle 126 and is in a stagnant state higher than the temperature of the liquid surface of the flowing portion including the primary jet 111 and the secondary jet 112, but in reality, the two temperatures are the same. On the liquid surface of the stagnant solder, a relatively thick oxide film is formed, or solder oxide (dross) floats, which makes the emissivity from the liquid surface relatively high, so the temperature difference described above occurs in the temperature measured by the infrared camera 170. By utilizing this feature, it becomes easy to separate the solder jet 110, including the primary jet 111 and secondary jet 112, from the portion of the solder jet 110 that has flowed out of the nozzle 126 and is retained there, making it easier to grasp the state of the solder jet 110.

25A and 25B, the positions and planar shapes of the primary jet 111 and secondary jet 112 can be seen from the temperature distribution in the thermal image 400. Furthermore, in FIG. 25A, a band-shaped region 401 is observed in the center of the temperature distribution in the secondary jet 112 region, which is lower in temperature than the surrounding area (the areas before and after along the conveying direction). On the other hand, in FIG. 25B, there is no low-temperature region like the band-shaped region 401 in FIG. 25A in the center 401x.

Furthermore, Figures 25A and 25B show schematic cross-sectional views of secondary jets 112 of solder jets 110 corresponding to the respective thermal images 400.

As shown in FIG. 25A, the low-temperature band-like region 401 occurs in a region where the inclination of the cross-sectional shape of the solder jet (secondary jet 112) is greatly changed. In particular, in the thermal image 400 in FIG. 25A, the low-temperature band-like region 401 is located near the end (downstream end in the transport direction) of the jet outlet 123, which corresponds to the region where the printed circuit board 103 leaves the solder jet 110 as shown in FIG. 23B and FIG. 24B. If the cross-sectional shape of the solder jet 110 changes significantly in such a region, there is a concern that the above-mentioned departure angle θwd will change from the appropriate value, resulting in a decrease in soldering quality.

On the other hand, as shown in FIG. 25B, when the change in the inclination of the cross-sectional shape of the solder jet (secondary jet 112) is small, it is understood that the low-temperature area (band-shaped region 401) as shown in FIG. 25A does not appear in the thermal image 400.

Figure 26 shows a conceptual cross-sectional view illustrating the relationship between the cross-sectional shape of a solder jet and the radiant energy to an infrared camera. The vertical axis of Figure 26 indicates the vertical position (z), and the horizontal axis of Figure 26 corresponds to the x-axis, with the transport direction being positive. As described above, the transport direction is tilted at a certain angle (e.g., about 5°) with respect to the x-axis along the horizontal plane, but in the thermal image 400 of the horizontal plane, the x-axis direction and the transport direction are synonymous.

Referring to the cross-sectional shape of the solder jet (secondary jet 112) shown at the bottom of Figure 26, in the vertical cross section of the solder jet, infrared radiation energy of the solder jet is emitted from each point on the outer periphery of the cross-sectional shape in the normal direction of the shape. In contrast, the infrared radiation energy from each measurement point 115 on the outer periphery captured by the infrared camera 107 depends on the direction cosine (cos θv) of the angle θv between the normal direction and the straight line (shown by the dotted line in the figure) connecting the measurement point 115 and the infrared camera 107.

Therefore, it can be understood that even among measurement points 115 with the same temperature, the detected temperature of the infrared camera 107 corresponding to a measurement point 115 with a large direction cosine cosθv will be higher, and the detected temperature of the infrared camera 107 corresponding to a measurement point 115 with a small direction cosine cosθ will be lower.

The upper part of Figure 26 shows a graph of cosθv corresponding to the cross-sectional shape of the solder jet (secondary jet 112). From this graph, it can be seen that cosθv changes in response to changes in the cross-sectional shape of the solder jet (secondary jet 112).

As a result, as shown in FIG. 27, an analogy is established between the distribution shape of cosθv at each measurement point on the outer circumference of the cross-sectional shape of the solder jet 110 and the temperature profile showing the distribution of the detected temperature Tdet by the infrared camera 107 at the measurement point.

26 and 27, in the cross-sectional area corresponding to the band-shaped region 401 in FIG. 25A, the change in the inclination of the cross-sectional shape of the solder jet is large, and therefore cosθv is lower than in the adjacent regions. As a result, in the region where the cross-sectional shape of the solder jet (secondary jet 112) changes and the inclination angle changes, a band-shaped region 401 with a lower temperature is observed than before and after along the x-axis direction due to the lower cosθv.

Therefore, it can be understood that by checking the presence or absence of low-temperature areas such as band-shaped region 401, as well as the width and position of the low-temperature areas based on the temperature distribution (temperature profile) on a straight line (x-axis) along the transport direction in a horizontal plane in thermal image 400, it is possible to monitor whether or not there is a disturbance in the cross-sectional shape of the solder jet that affects the separation angle θwd (specifically, a large change in inclination). For example, the above-mentioned monitoring can be performed by visually checking thermal image 400 displayed as a color image on display unit 109.

Alternatively, it is possible to quantitatively perform the above-mentioned monitoring by calculating an evaluation parameter value for evaluating the cross-sectional shape of the solder jet in the first vertical cross section along the transport direction from the temperature distribution (temperature profile) of the detection temperature Tdet acquired by the thermal image 400, and comparing the evaluation parameter value with a predetermined judgment value.

In this way, it is possible to judge whether the cross-sectional shape of the solder jet is good or bad from the temperature distribution along the x-axis direction (transport direction) of the temperature Tdet detected by the infrared camera 107 in the horizontal plane of the thermal image 400, particularly in the area corresponding to the secondary jet 112. For example, it is possible to adjust the angle of the nozzle 126 or the rotation speed of the motor 108 based on the judgment result, thereby adjusting the separation angle θwd.

Furthermore, changes in the flow rate of the solder jet can also be monitored using the same temperature distribution.

The lower part of Figure 28 shows the change in the cross-sectional shape of the solder jet in response to changes in the flow rate of the solder jet. Compared to cross-sectional profile 461 at an appropriate flow rate, cross-sectional profile 460 at a large flow rate and cross-sectional profile 462 at a small flow rate have different outer peripheral shapes.

28, the temperature profile 450 when the flow rate is large expands in the x-axis direction and the valley of the temperature distribution moves in the positive x-axis direction with respect to the temperature profile 451 when the flow rate is appropriate, as shown in the upper part of FIG. 28. On the other hand, the temperature profile 452 when the flow rate is small contracts in the x-axis direction and the valley of the temperature distribution moves in the negative x-axis direction with respect to the temperature profile 451 when the flow rate is appropriate. Therefore, by monitoring the temperature profile of the solder jet 110 along the x-axis direction, it is possible to monitor the flow rate of the solder jet 110. For example, a reference flow rate thermal image at the appropriate flow rate when the temperature of the solder jet 110 is controlled at a predetermined temperature is determined in advance, and the flow rate change of the solder jet 110 is easily detected based on a comparison between the reference flow rate thermal image and the current thermal image 400 by visually observing the thermal image 400 or by monitoring based on the above-mentioned evaluation parameter value. By adjusting the rotation speed of the motor 108 etc. in response to the detection of such flow rate changes, it is possible to maintain and manage the same solder jet state.

Thermal image 400 can also be used to monitor the primary jet 111 of the solder jet 110.

Figures 29A and 29B show a thermal image 400 of the primary jet 111 of the solder jet 110, and a graph showing the distribution of the detected temperature Tdet in the width direction within the surface of the thermal image 400.

Figure 29A shows an example of temperature distribution under normal conditions when no nozzles are clogged, while Figure 29B shows an example of temperature distribution under abnormal conditions when some nozzles are clogged.

29A further shows a graph indicating the distribution of the detected temperature Tdet for positions on line A-A in the thermal image 400. Similarly, FIG. 29B shows a graph indicating the distribution of the detected temperature Tdet for positions on line B-B in the thermal image 400. The lines A-A and B-B are lines along a direction perpendicular to the transport direction (hereinafter also referred to as the "width direction") in a horizontal plane. The graphs in FIG. 29A and FIG. 29B are written with the horizontal and vertical axes rotated 90 degrees, and the horizontal axis indicates the position (y coordinate) on line A-A or line B-B. These graphs show the temperature profile of the solder jet (primary jet) 111 along the width direction.

In FIG. 29B, low temperature areas 470, 471 corresponding to the clogged nozzle are present in the thermal image 400, and in the widthwise temperature profile, an area of reduced detected temperature Tdet occurs corresponding to the low temperature area 470 located on line B-B. In the area where the nozzle is clogged, the shape of the solder jet (primary jet 111) becomes distorted and the infrared radiation energy decreases, causing a decrease in the detected temperature Tdet of that area by the infrared camera 107.

In contrast, in Figure 29A, there are no localized low temperature areas like the low temperature areas 470 and 471 in Figure 29B. In the temperature distribution (profile) on line A-A, there are no areas of temperature drop corresponding to nozzle clogging, like the area on line B-B in Figure 29B.

In this way, the primary jet 111 can also be monitored for the occurrence of nozzle clogging based on the temperature profile in the width direction in the thermal image 400. The determination of the occurrence of nozzle clogging is equivalent to the evaluation of the shape of the vertical cross section (hereinafter also referred to as the second vertical cross section) of the primary jet 111 (solder jet 110) along the width direction (the direction of the straight lines A-A and B-B in Figures 29A and 29B). This monitoring can also be performed by visually inspecting the thermal image 400, or based on evaluation parameter values that reflect the temperature distribution appearing in the thermal image 400. In this way, the vertical cross-sectional shape of the solder jet 110, more specifically, the shape of the secondary jet 112 in the first vertical cross section along the transport direction, and the shape of the primary jet 111 in the second vertical cross section along the width direction can be evaluated based on the temperature distribution within the surface of the thermal image 400.

The evaluation parameter values for quantitatively evaluating the temperature distribution appearing in such a thermal image 400 (thermal image of the solder jet 110) can also be efficiently calculated based on the temperature detection values in the inspection frames provided corresponding to the primary jet 111 and the secondary jet 112, similar to the thermal image 250 (thermal image of the thin plate 201) described in the second embodiment.

Figure 30A shows a conceptual diagram illustrating an example of setting an inspection frame for monitoring the primary jet 111.

As shown in FIG. 30A, multiple inspection frames 510 can be provided in the thermal image 400 to correspond to the ejection shape of the primary jet 111. In other words, the positions of the multiple inspection frames 510 can be determined in advance to correspond to the arrangement area of the nozzle that ejects the primary jet 111.

For example, in each inspection frame 510, the average value of the detected temperatures Tdet at multiple pixels contained in that inspection frame 510 can be calculated as the evaluation parameter value. Then, in an inspection frame 510 where the evaluation parameter value (average temperature) is lower than a predetermined judgment temperature, it can be determined that the corresponding nozzle is clogged. Alternatively, it is also possible to further calculate the average value (overall average value) of the evaluation parameter values of each of the multiple inspection frames 510, and compare it with the overall average value to detect nozzle clogging in an inspection frame 510 where the evaluation parameter value is lower by more than a certain value.

Figure 30B shows a conceptual diagram illustrating an example of setting an inspection frame for monitoring the secondary jet 112.

30B , in order to evaluate the departure angle θwd, the position of inspection frame 511 of secondary jet 112 can be set to correspond to the portion where printed circuit board 103 leaves solder jet 110. Then, the average value of detected temperatures Tdet at multiple pixels included in inspection frame 511 can be calculated as the evaluation parameter value.

For example, when the evaluation parameter value is lower than a judgment temperature determined based on the temperature of the solder jet 110, it can be determined that a change (Figure 25A) has occurred in the cross-sectional shape (vertical cross section along the transport direction) of the solder jet (secondary jet 112) that affects the separation angle θwd.

Alternatively, instead of comparing with the judgment value, it is also possible to further set a comparative inspection frame (not shown) adjacent to the inspection frame 511 in the transport direction, further calculate the evaluation parameter values (average temperature) of the comparative inspection frame and the inspection frame 511, and when a difference in average temperature occurs between the inspection frame 511 and the comparative inspection frame that is equal to or greater than a certain value, it is possible to determine that a change in the cross-sectional shape of the solder jet (secondary jet 112) described above has occurred.

Alternatively, similar to the thermal image 250 (thermal image of the thin plate 201) described in the second embodiment, it is also possible to determine whether the condition of the solder jet 110 is good or bad by comparing a predetermined normal thermal image of the thermal image 400 (solder jet 110) with the actual thermal image taken by the infrared camera 107 by pattern matching.

In addition, considering that the solder jet 110 is a fluid, in order to reduce fluctuations in the measurement data (temperature detection values) due to fluctuations in the liquid surface, it is also possible to obtain a thermal image for evaluating the solder jet, i.e., temperature distribution data, from the measurement data (temperature detection values) obtained by averaging thermal images 400 taken at different times.

Figure 31 is a flowchart explaining the method for evaluating solder jets and the method for manufacturing printed circuit boards according to embodiment 4.

Referring to FIG. 31, the manufacturing process of the printed circuit board according to the fourth embodiment includes a solder jet evaluation process P101 and a soldering process P200. The solder jet evaluation process P101 includes steps S101 and S111 relating to a thermal image 250 of the evaluation device (thin plate 201) in contact with the solder jet 110, steps S201 and S211 relating to a thermal image 400 of the solder jet 110, step S121, and steps S130 to S180 similar to those in FIG. 19. The processing of each step included in the solder jet evaluation process P101 is executed by, for example, the controller 300 (FIG. 3).

S101 and S111 are realized by the same process as S100 and S110 in FIG. 19. That is, in S101, the controller 300 photographs the thin plate 201 of the evaluation device 200 described in the first embodiment with the infrared camera 107 while the thin plate 201 is in contact with the solder jet 110 above the molten solder bath 102, thereby acquiring thermal imaging data (thermal image 250) showing the temperature distribution within the surface of the thin plate 201. As a result, the controller 300 acquires the temperature detection value by the infrared camera 107 in the thermal image 250 as the thermal imaging data. Furthermore, in step S102, a predetermined evaluation parameter value (corresponding to the "first evaluation parameter value") showing the feature amount of the captured thermal image 250 is calculated. As described above, various values for quantitatively expressing the temperature distribution can be used for the evaluation parameter value.

In S201, the controller 300 captures thermal imaging data (thermal image 400) showing the temperature distribution in the horizontal plane of the solder jet 110 by photographing the molten solder bath 102 with the infrared camera 107 without passing through the transported object on the transport conveyor 104. As a result, the controller 300 captures the temperature detection value by the infrared camera 107 at each pixel of the thermal image 400 as thermal imaging data. Furthermore, in S202, a predetermined evaluation parameter value (corresponding to the "second evaluation parameter value") showing the characteristic amount of the captured thermal image 400 is calculated. As described above, the evaluation parameter value can be various values for quantitatively expressing the temperature distribution in addition to the examples in the fourth embodiment.

The controller 300 can execute S101 and S111 in response to the infrared camera 107 capturing the thermal image 250 at the timing when the evaluation device 200 (thin plate 201) is transported by the transport conveyor 104 and passes over the solder jet.

Furthermore, the controller 300 can execute the processes of S201 and S211 in response to the infrared camera 107 capturing the thermal image 400 before or after the timing of capturing the thermal image 250. In this way, the processes of S101 and S111, and the processes of S201 and S211 can be executed in any order. Alternatively, depending on the capabilities of the controller 300, the processes of S111 and S211 can be executed in parallel.

In S121, the controller 300 executes a quality judgment process for the state of the solder jet 110 based on both the thermal image 250 and the thermal image 400. The quality judgment process based on the thermal image 250 can be executed in the same manner as described in FIG. 19. Furthermore, the quality judgment process for the thermal image 400 can also be executed by comparing the evaluation parameter value that quantitatively indicates the temperature distribution with the judgment value, or by pattern matching with a reference image.

In this way, in S121, it is possible to further evaluate the vertical cross-sectional shape of the solder jet 110 as described in the fourth embodiment, and to determine whether the state of the solder jet 110 is good or bad. This makes it possible to determine whether the state of the solder jet 110 is good or bad, taking into account the departure angle θwd, which is difficult to determine from the thermal image 250 of the thin plate 201.

In S121, the controller 300 can also execute the defect cause determination process using the evaluation parameter values described in FIG. 19 in a manner that further incorporates the defect cause of the vertical cross-sectional shape of the solder jet 110. For example, the machine learning model described in FIG. 20 can be configured to further incorporate the evaluation parameter values (input layer) and defect cause (output layer) related to the vertical cross-sectional shape of the solder jet 110.

In S130, the controller 300 outputs the results of the pass/fail judgment process and the defect cause judgment process in S121, including the judgment result related to the vertical cross-sectional shape of the solder jet 110 based on the thermal image 400. As a result, in FIG. 31, the pass/fail judgment of the solder jet is performed, including the vertical cross-sectional shape of the solder jet 110. In addition, in S130, the regression prediction shown in FIG. 21 is also performed on the evaluation parameter values based on the thermal image 400, and it is possible to further output time-series regression prediction information related to the vertical cross-sectional shape of the solder jet 110.

The processing of S170, S180 and the soldering process P200 for the pass/fail judgment result of the solder jet 110 are the same as those in FIG. 19, so detailed explanations will not be repeated. In addition to the explanation in FIG. 19, S180 can also output adjustment guidance related to the vertical cross-sectional shape of the solder jet 110 and perform automatic adjustment of the equipment (motor 108, nozzle 126, etc.).

In addition, in the processes of S150 and S160, the controller 300 can also convert the evaluation parameter values calculated from the thermal image 400 into training data and store them in the database 360 for machine learning.

In this way, according to the solder jet evaluation method of the fourth embodiment, in addition to the solder jet evaluation test using the evaluation device 200 described in the first to third embodiments, the vertical cross-sectional shape of the solder jet 110 (the first vertical cross section along the transport direction and the second vertical cross section along the width direction) is also evaluated, so that the solder jet evaluation test can be performed with higher accuracy. This makes it possible to suppress deterioration of soldering quality caused by defects in the separation angle θwd during soldering, in addition to the effects of the first to third embodiments. Furthermore, by confirming that the condition of the solder jet 110 is good using the solder jet evaluation method of the fourth embodiment, and then realizing a manufacturing process in which the printed circuit board 103 is continuously soldered, the occurrence of defective products can be further suppressed.

Figure 32 is a flowchart explaining a method for evaluating solder jets according to a modified example of embodiment 4.

As shown in FIG. 32, the solder jet evaluation method according to the modified embodiment of the fourth embodiment includes a solder jet evaluation process P102 and a soldering process P200. In the solder jet evaluation process P102, steps S101 and S111 are omitted from the solder jet evaluation process P101 in FIG. 31. As a result, in the solder jet evaluation process P102, a quality determination process (S122) of the state of the solder jet 110 is performed based only on the thermal image 400 of the solder jet 110. Therefore, based on the evaluation result of the vertical cross-sectional shape of the solder jet 110, adjustment guidance is output (S180), etc., to prevent the soldering process (P200) from being performed using a solder jet having an inappropriate cross-sectional shape.

The solder jet evaluation method shown in FIG. 32 can be performed in a short time without the need to transport the evaluation device 200 (thin plate 201). Therefore, the solder jet evaluation process P102 can be performed multiple times without requiring a long time, for example, after the start of the soldering process P200. This increases the frequency of checking the vertical cross-sectional shape of the solder jet 110, allowing for early detection of abnormalities in the solder jet 110, thereby further improving the quality of the soldering process.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

100 soldering device, 101 housing, 102 molten solder bath, 103 printed circuit board, 104 conveyor, 105 preheater, 106 preheater, 107 infrared camera, 108 motor, 109 display unit, 110 solder jet, 111 primary jet, 111c, 111x, 111y, 111z, 112c, 510, 511, 512 inspection frame, 111t, 112c isotherm, 112, 112x secondary jet, 121 heater, 122 foreign matter, 123 jet nozzle, 124 impeller, 125 adjustment bolt, 200 evaluation device, 201 thin plate, 210 conveying member, 211 upper jig, 212 lower jig, 213 spacer, 214 Knurled screw, 215 Positioning pin, 216, 222 Bolt, 217, 218, 221 Gap, 219 Space, 220 Reinforcement, 250 Thermal image (thin plate), 252 Processing image, 300 Controller, 320 Memory, 350 Bus, 360 Database, 370 Neural network, 380 Regression line, 400 Thermal image (solder jet), 401 Band area, 401x Center, 450, 451, 452 Temperature profile, 460, 461, 462 Cross-sectional profile, 470, 471 Low temperature area.

Claims (8)

A solder jet evaluation device for use in a soldering apparatus including a molten solder bath from which a solder jet is jetted, a transport conveyor for transporting an object to be soldered so as to pass above the molten solder bath, and a temperature distribution measuring device within a field of view directed from above the molten solder bath toward the transport conveyor and the molten solder bath, comprising:
A conveying member conveyed on the conveyor;
a thin plate member attached to the conveying member at a position above the molten solder bath where the thin plate member comes into contact with the solder jet,
The thin plate member is made of a material and has a plate thickness of 0.1 or less. the thin plate member is attached to the conveying member such that a first gap is provided between the thin plate member and the conveying member along a plate thickness direction of the thin plate member,
2. The solder jet evaluation device according to claim 1, wherein the first gap is larger than an amount of thermal expansion in the thickness direction that occurs in the thin plate member when the thin plate member comes into contact with the solder jet. the thin plate member is attached to the conveying member such that a second gap is provided between the thin plate member and the conveying member along a surface direction of the thin plate member,
3. The solder jet evaluation device according to claim 1, wherein the second gap is larger than an amount of thermal expansion in the planar direction that occurs in the thin plate member when the thin plate member comes into contact with the solder jet. the thin plate member is attached to the conveying member by a fixing member passing through a hole provided in the thin plate member,
A solder jet evaluation device as described in any one of claims 1 to 3, wherein a third gap in the surface direction of the thin plate member caused by the difference between the diameter of the hole and the diameter of the fixing member is larger than the amount of thermal expansion in the surface direction that occurs in the fixing member when it comes into contact with the solder jet. The transport member is configured to have a first side and a second side extending in a direction intersecting a transport direction of the transport conveyor,
the first side is transported on the transport conveyor in the transport direction ahead of the second side,
the thin plate member is attached to the conveying member such that a space is provided between the thin plate member and the second side,
5. The solder jet evaluation device according to claim 1, wherein the length of the space along the transport direction is longer than (1/2) the length of the solder jet along the transport direction. The solder jet evaluation device according to any one of claims 1 to 4, wherein the transport member is configured in a shape that opens on the rear side along the transport direction of the transport conveyor when the thin plate member is attached. The conveying member is
a first member to which the thin plate member is attached; and
a second member fixed to the first member,
the first member has a shape that opens at a rear side along a conveying direction of the conveyor when the thin plate member is attached,
The solder jet evaluation device according to any one of claims 1 to 4, wherein the second member is attached to the first member so as to be positioned above the thin plate member in correspondence with an opening portion of the first member. The solder jet evaluation device according to any one of claims 1 to 7,
the soldering device to be evaluated by the evaluation device;
and a controller that determines whether the state of the solder jet is good or bad based on the temperature distribution within the surface of the thin plate member obtained by image processing of a thermal image obtained by measuring the thin plate member in contact with the solder jet using the temperature distribution measuring device when the evaluation device passes above the molten solder bath.

Images