JP7535722B2 - Manufacturing method and manufacturing device for solder precoated substrate - Google Patents

Description

This disclosure relates to a method and apparatus for manufacturing a solder precoated substrate.

Conventionally, a method of forming a solder precoat on the lands of a substrate is known (for example, see Patent Document 1). In the method of this document, the openings of a mask are aligned with the lands to cover the substrate, and solder paste is then supplied to the openings to transfer the solder paste onto the lands. The transferred solder paste is melted to form a solder precoat.

Japanese Patent Application Publication No. 7-302972

However, as electronic components mounted on a board become smaller, the distance between adjacent lands also tends to become shorter. When the distance between lands is short, it is possible to prevent adjacent solder precoats from connecting with each other (hereinafter referred to as the bridging phenomenon) by forming a solder precoat using a solder paste that contains solder particles with a very small particle diameter.

However, solder paste containing solder particles with small particle diameters is expensive, and its use leads to increased manufacturing costs for substrates on which a solder precoat is formed (hereinafter, solder precoated substrates). In this situation, one of the objectives of the present disclosure is to provide a method for manufacturing a solder precoated substrate that can reduce manufacturing costs.

One aspect of the present disclosure relates to a method for manufacturing a solder precoated substrate by forming a solder precoat on a plurality of lands provided on a surface of a substrate. The method for manufacturing the solder precoated substrate includes a supplying step of supplying solder paste to the plurality of lands, and a heating step of heating the substrate so that the temperature of the plurality of lands reaches the melting point of the solder particles contained in the solder paste faster than the surface temperature of the substrate around the lands.

Another aspect of the present disclosure relates to an apparatus for manufacturing a solder precoated substrate by forming a solder precoat on a plurality of lands provided on the surface of a substrate. The apparatus for manufacturing a solder precoated substrate includes a supply unit that supplies solder paste to the plurality of lands, and a heating unit that heats the substrate so that the temperature of the plurality of lands reaches the melting point of the solder particles contained in the solder paste faster than the surface temperature of the substrate around the lands.

This disclosure provides a method and apparatus for manufacturing solder precoated substrates that can reduce manufacturing costs.

1 is a front view showing an example of a manufacturing apparatus for a solder precoated substrate according to a first embodiment. FIG. 1 is a side view showing a part of a manufacturing apparatus for a solder precoated substrate according to a first embodiment. 1 is a side view showing a part of a manufacturing apparatus for a solder precoated substrate according to a first embodiment. FIG. 2 is a schematic diagram for explaining a heating unit and a heating step according to the first embodiment. 10 is a schematic diagram for explaining a heating unit and a heating step according to a modified example of the first embodiment. FIG. FIG. 11 is a perspective view showing a part of a manufacturing apparatus for a solder precoated substrate according to a second embodiment. 11 is a schematic diagram for explaining a heating unit and a heating step according to a second embodiment. FIG.

The following describes an embodiment of a manufacturing method and manufacturing apparatus for a solder precoated substrate according to the present disclosure. However, the present disclosure is not limited to the examples described below.

The method for manufacturing a solder precoated substrate according to the present disclosure is a method for manufacturing a solder precoated substrate by forming a solder precoat on a plurality of lands provided on the surface of a substrate, and includes a supplying step of supplying solder paste to the plurality of lands, and a heating step of heating the substrate so that the temperature of the plurality of lands reaches the melting point of the solder particles contained in the solder paste faster than the surface temperature of the substrate around the lands.

In the supplying process, solder paste is supplied to a number of lands provided on the surface of the substrate. Any method can be used for this supply. For example, the solder paste can be supplied by a screen printing method, but this is not limiting.

In the heating process, the substrate is heated, and the temperature of the lands reaches the melting point of the solder particles contained in the solder paste faster than the surface temperature of the substrate around them. This causes the solder particles to melt and gather on the surface of the lands. In this disclosure, these melted solder particles are referred to as molten solder nuclei. As the substrate is heated, the molten solder nuclei grow by attracting the surrounding solder particles contained in the solder paste. In this way, the solder particles contained in the solder paste gather on the lands, and the solder precoat formed thereafter also remains on the lands. As a result, the occurrence of the bridge phenomenon can be suppressed even when a solder paste containing solder particles with a large particle size is used.

In this case, any heating method can be used in the heating step. For example, the substrate may be heated using a reflow furnace, a heating plate, or an induction heating device, but is not limited to these.

In the heating process, the substrate may be heated more strongly from the back side of the substrate than from the front side of the substrate. This causes the temperature of the lands to rise faster than the surface temperature of the substrate around them. This is because the lands made of metal have a higher thermal conductivity than the substrate around them, and the strong heat from the back side of the substrate is relatively easily transmitted.

In the heating process, the substrate may be heated only from the back side of the substrate. This causes the temperature of the lands to rise faster than the surface temperature of the surrounding substrate. This is because the lands made of metal have a higher thermal conductivity than the surrounding substrate, and heat from the back side of the substrate is relatively more easily transferred thereto.

In the heating step, the substrate may be heated so that the temperature of the substrate surface increases at a rate of increase of 4°C/sec or more. By increasing the substrate surface temperature at such a rate of increase, the occurrence of the bridge phenomenon can be further suppressed.

In the heating step, the substrate may be heated using a heating plate that contacts the rear surface of the substrate. The heat of the heating plate is easily transferred to the land, which has high thermal conductivity. Therefore, the temperature of the land rises faster than the surface temperature of the substrate around it.

In the heating step, the substrate may be heated with a sheet sandwiched between the substrate and the heating plate. By sandwiching the sheet, it is possible to prevent the substrate from being scratched or soiled by contact with the heating plate.

The sheet may be made of a material (e.g., silicon) that is softer than the substrate and the heating plate. The soft sheet can be deformed to conform to the surface shapes of the substrate and the heating plate, improving heat transfer from the heating plate to the substrate.

In the heating step, the substrate may be heated while being held down at multiple points. This can prevent the substrate from warping due to heating.

The method for manufacturing a solder precoated substrate may further include a cooling step of cooling the substrate while pressing the substrate at multiple points after the heating step. This can prevent the substrate from warping due to cooling.

The manufacturing apparatus for solder precoated substrates according to the present disclosure is an apparatus for manufacturing solder precoated substrates by forming a solder precoat on a plurality of lands provided on the surface of a substrate, and includes a supply unit that supplies solder paste to the plurality of lands, and a heating unit that heats the substrate so that the temperature of the plurality of lands reaches the melting point of the solder particles contained in the solder paste faster than the surface temperature of the substrate around the lands.

The supply unit supplies solder paste to multiple lands provided on the surface of the board. Any type of supply unit can be used. For example, a squeegee for screen printing could be used, but this is not a limitation.

The heating unit heats the board so that the temperature of the multiple lands reaches the melting point of the solder particles contained in the solder paste faster than the surface temperature of the surrounding board. This causes the solder particles to melt and gather on the surface of the land to form a molten solder nucleus. As the board is heated, the molten solder nucleus grows by attracting the surrounding solder particles contained in the solder paste. In this way, the solder particles contained in the solder paste gather on the land, and the solder precoat formed thereafter also remains on the land. As a result, the occurrence of the bridge phenomenon can be suppressed even when using a solder paste containing solder particles with a large particle size.

Here, any type of heating unit can be used. For example, a reflow furnace, a heating plate, or an induction heating device can be used, but is not limited to these.

The heating unit may heat the substrate more strongly from the back side of the substrate than from the front side of the substrate. This causes the temperature of the lands to rise faster than the surface temperature of the substrate around them. This is because the lands made of metal have a higher thermal conductivity than the substrate around them, and the strong heat from the back side of the substrate is relatively easily transmitted.

The heating section may heat the substrate only from the back side of the substrate. This causes the temperature of the lands to rise faster than the surface temperature of the substrate around them. This is because the lands made of metal have a higher thermal conductivity than the substrate around them, and heat from the back side of the substrate is relatively more easily transferred to them.

The heating section may heat the substrate so that the temperature of the substrate surface increases at a rate of increase of 4°C/sec or more. By increasing the substrate surface temperature at such a rate of increase, the occurrence of the bridge phenomenon can be further suppressed.

The heating section may have a heating plate that contacts the back surface of the substrate to heat the substrate. The heat of the heating plate is easily transferred to the land, which has a high thermal conductivity. Therefore, the temperature of the land rises faster than the surface temperature of the substrate around it.

The manufacturing apparatus for solder precoated substrates may further include a sheet that is sandwiched between the substrate and the heating plate when the substrate is heated. By sandwiching the sheet, it is possible to prevent the substrate from being scratched or soiled by contact with the heating plate.

The manufacturing device for solder precoated substrates may further include a heating holding section that holds the substrate at multiple points when the substrate is heated. Such a heating holding section can prevent the substrate from warping due to heating.

The manufacturing device for solder precoated substrates may further include a cooling section that cools the heated substrate, and a cooling holding section that holds the substrate at multiple points while the substrate is being cooled. Such a cooling holding section can prevent the substrate from warping due to cooling.

Below, examples of the manufacturing method and manufacturing apparatus for solder precoated substrates according to the present disclosure will be specifically described with reference to the drawings. The above-mentioned processes and components can be applied to the steps of the manufacturing method and components of the manufacturing apparatus for solder precoated substrates described below. The steps of the manufacturing method and components of the manufacturing apparatus for solder precoated substrates described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiment. Among the steps of the manufacturing method and components of the manufacturing apparatus for solder precoated substrates described below, steps and components that are not essential to the manufacturing method and manufacturing apparatus for solder precoated substrates according to the present disclosure may be omitted.

First Embodiment
A description will be given of a first embodiment of the present disclosure. First, the configuration of a manufacturing apparatus 10 for a solder precoated substrate (hereinafter, also simply referred to as a "manufacturing apparatus 10") will be described, and then a manufacturing method for a solder precoated substrate (hereinafter, also simply referred to as a "manufacturing method") will be described.

- Manufacturing equipment for solder precoated circuit boards -
1 to 3 is an apparatus for manufacturing a solder precoated substrate by forming a solder precoat on a plurality of lands 3 (see FIG. 4) provided on the surface of a substrate 1. In this specification, the direction in which the substrate 1 is transported is defined as the X direction, the vertical direction is defined as the Z direction, and the direction perpendicular to the X and Z directions is defined as the Y direction. The axes along each of these directions are defined as the X axis, the Y axis, and the Z axis.

As shown in FIG. 1, the manufacturing apparatus 10 includes a supply unit 100, a heating unit 210, a cooling unit 220, and a control unit 20. The supply unit 100, the heating unit 210, and the cooling unit 220 are arranged in a row in the X direction on the base 101. For ease of understanding, FIG. 1 shows an example in which a substrate 1 is arranged in each of the supply unit 100, the heating unit 210, and the cooling unit 220.

(Supply Department)
The supply unit 100 supplies the solder paste P to the lands 3 of the substrate 1 by screen printing. Note that the supply unit 100 may supply the solder paste P to the lands 3 by a method other than screen printing.

The supply section 100 has a moving table 102, a lifting mechanism 103, a printing stage 104, a printing head 113, a mask plate 116, a printing stage conveyor 231, a substrate input conveyor 234, and a substrate relay conveyor 232.

The moving table 102 is disposed between a pair of support frames 11 that are spaced apart in the X direction on the base 101. A lifting mechanism 103 that raises and lowers the print stage 104 is disposed on the moving table 102.

The printing stage 104 has a base 104a that is connected to the lifting mechanism 103. A support pillar 104b is provided on the upper surface of the base 104a. A board guide 104c that extends along the X-axis is connected to the upper end of the support pillar 104b. A printing stage conveyor 231 including a belt for transporting the board 1 is arranged inside the board guide 104c.

The moving table 102 moves the lifting mechanism 103 horizontally, i.e., along the X-axis and Y-axis, thereby moving the printing stage 104 horizontally. The moving table 102 rotates the lifting mechanism 103 around the Z-axis, thereby rotating the printing stage 104 around the Z-axis. The lifting mechanism 103 moves the printing stage 104 along the Z-axis, i.e., raises and lowers it.

The printing stage conveyor 231 is configured to transfer the substrate 1 between the substrate carry-in conveyor 234 arranged to pass through the opening of one of the support frames 11 and the substrate relay conveyor 232 arranged to pass through the opening of the other support frame 11. The substrate 1 carried in by the substrate carry-in conveyor 234 is transferred to the printing stage conveyor 231 and transported to the solder paste supply area PA, where it is held by the printing stage 104. The substrate 1 to which the solder paste P has been supplied by the printing stage 104 is transferred out of the solder paste supply area PA of the printing stage conveyor 231 and transferred to the substrate relay conveyor 232.

A backup lifting mechanism 104e is disposed on the upper surface of the base 104a. The backup lifting mechanism 104e raises and lowers the backup section 104f, which supports the substrate 1 from below. When the substrate 1 is carried into the solder paste supply area PA of the print stage conveyor 231, the backup section 104f is raised to support the lower surface of the substrate 1.

A side clamper 104d extending along the X-axis is provided on the upper surface of each of the pair of board guides 104c. The side clamper 104d is opened and closed by a drive mechanism (not shown). The backup section 104f supports the lower surface of the board 1 while raising the board 1 to a height where the upper surface of the board 1 and the upper surface of the side clamper 104d are substantially flush with each other. When the board 1 and the side clamper 104d are at the same height, the side clamper 104d closes, whereby both side surfaces of the board 1 are sandwiched between the side clampers 104d and the board 1 is fixed. In this way, the printing stage 104 holds the board 1.

A support beam 113a that supports the print head 113 is disposed at the upper ends of the pair of support frames 11 so as to be movable along the Y axis via a linear guide mechanism 11a. One end of the support beam 113a is connected to a well-known print head moving mechanism 11b that is composed of a feed screw and a motor that rotates the feed screw. When the print head moving mechanism 11b is driven, the print head 113 moves back and forth (squeezing operation) along the Y axis.

As shown in FIG. 2, the print head 113 has a rear squeegee 113b and a front squeegee 113c that extend downward from the support beam 113a. When the squeegee driver 113d provided on the upper surface of the support beam 113a is driven, either the rear squeegee 113b or the front squeegee 113c descends depending on the direction of the squeegeeing operation.

A mask plate 116 is disposed horizontally below the print head 113. The mask plate 116 is formed with pattern holes (not shown) penetrating in the thickness direction. The pattern holes are formed to correspond to the arrangement and shape of the multiple lands 3 on the substrate 1. The supply unit 100 performs screen printing to supply the solder paste P onto the substrate 1 in a predetermined printing pattern by moving the solder paste P (see FIG. 3) supplied to the upper surface of the mask plate 116 with the rear squeegee 113b or the front squeegee 113c.

(Heating section)
The heating unit 210 heats the solder paste P supplied to the lands 3 to melt the solder particles PL contained in the solder paste P. The heating unit 210 has a housing 213 that covers the downstream side of the board relay conveyor 232 extending from the supply unit 100, and a first heater 211 and a second heater 212 arranged inside the housing 213. The housing 213 is formed with an air hole 215 for exhausting volatile components from the solder paste P that are generated by heating.

The first heater 211 is disposed below the substrate relay conveyor 232. When viewed from below, the first heater 211 covers the entire substrate 1 located in the heating area HA. The first heater 211 heats the entire substrate 1 located in the heating area HA from below (i.e., from the back side of the substrate 1).

In this embodiment, the board relay conveyor 232 is composed of a metal chain extending along the transport direction of the board 1 (see FIG. 4), but is not limited to this.

The second heater 212 is disposed above the substrate relay conveyor 232. When viewed from above, the second heater 212 covers the entire substrate 1 located in the heating area HA. The second heater 212 heats the entire substrate 1 located in the heating area HA from above (i.e., from the front surface side of the substrate 1). Alternatively, the second heater 212 does not have to heat the substrate 1 located in the heating area HA (i.e., it may be turned off).

The first heater 211 and the second heater 212 preferably heat the substrate 1 so that the surface temperature of the substrate 1 rises at a rate of increase of 4°C/sec or more. By heating the substrate 1 at such a rate of increase, the occurrence of the bridge phenomenon can be further suppressed. As the rate of increase, it is possible to use the value of (200-100)/Δt (unit: °C/sec), where Δt (unit: seconds) is the time required for the surface temperature of the substrate 1 to rise from 100°C to 200°C, but this is not limiting.

(Cooling section)
The cooling section 220 cools and solidifies the molten solder particles PL (hereinafter also referred to as "molten solder"). The cooling section 220 has a housing 224 that covers the board discharge conveyor 233, and a cooling fan 221 arranged inside the housing 224. The housing 224 has vent holes 220a, 220b for introducing and discharging cooling air. The cooling fan 221 cools the board 1 on the board discharge conveyor 233. This cools and solidifies the molten solder.

(Control Unit)
The control unit 20 controls the supply unit 100, the heating unit 210, the cooling unit 220, and each of the conveyors 231 to 234 to cause the manufacturing apparatus 10 to execute the operation of forming a solder precoat on the substrate 1. The control unit 20 is provided inside the base 101. The control unit 20 is composed of a central processing unit (CPU), a storage device (memory) that stores a program executable by the central processing unit, and the like.

- Circuit board configuration -
Next, a description will be given of the configuration of the substrate 1. As shown in Fig. 4, the substrate 1 of this embodiment has a substrate body 2, a plurality of lands 3 provided on the obverse surface (upper surface) of the substrate body 2, and a plurality of wiring patterns 4 connected to the lands 3 and exposed on the reverse surface (lower surface) of the substrate body 2. The substrate body 2 is made of an insulator, while the plurality of lands 3 and the wiring patterns 4 are made of conductors.

Thus, the substrate 1 of this embodiment is a double-sided printed circuit board, but the type of substrate 1 is not limited to this. For example, the substrate 1 may be a single-sided printed circuit board or a multilayer printed circuit board. The manufacturing apparatus and manufacturing method disclosed herein can be applied to any type of substrate 1.

-Method for manufacturing solder precoated substrate-
Next, a manufacturing method of this embodiment will be described. The manufacturing method includes a supplying step, a heating step, and a cooling step.

(Supply process)
In the supply step, solder paste P is supplied to a plurality of lands 3 provided on the surface of the substrate 1. Specifically, the control unit 20 operates the substrate carry-in conveyor 234 and the printing stage conveyor 231 to transport the substrate 1 on which no solder precoat has been formed to the solder paste supply area PA. Next, the control unit 20 operates the backup lifting mechanism 104e to cause the backup unit 104f to support the substrate 1, and causes the side clamper 104d to clamp the substrate 1. As a result, the printing stage 104 holds the substrate 1.

Next, the control unit 20 aligns the horizontal position of the substrate 1 relative to the mask plate 116, and then drives the lifting mechanism 103 to raise the substrate 1 and bring it into contact with the underside of the mask plate 116. The control unit 20 then operates the print head 113 to screen print the solder paste P onto the substrate 1.

Next, the control unit 20 drives the lifting mechanism 103 to separate the substrate 1 from the mask plate 116 (plate release). The control unit 20 then operates the side clamper 104d and the backup lifting mechanism 104e to release the substrate 1 from the side clamper 104d, and lowers the backup unit 104f to place the substrate 1 on the print stage conveyor 231. The control unit 20 then operates the print stage conveyor 231 and the substrate relay conveyor 232 to transport the substrate 1 to the heating area HA in the heating unit 210.

(Heating process)
In the heating step, the substrate 1 with the solder paste P supplied onto the lands 3 is heated by the first heater 211 and the second heater 212, or by only the first heater 211. Specifically, as shown in Fig. 4, the control unit 20 operates the first heater 211 at a high temperature to heat the substrate 1 from the back surface side (lower surface side). The control unit 20 operates the second heater 212 at a low temperature to heat the substrate 1 from the front surface side (upper surface side), or does not operate the second heater 212.

When the first heater 211 and the second heater 212 are controlled in this manner, the first heater 211, which has a relatively high output, becomes the main heat source, and the substrate 1 is heated more strongly from the back side than from the front side in the heating area HA. The heat of the first heater 211, which serves as the main heat source, is transferred to the land 3 via the wiring pattern 4. As a result, the temperature of each land 3 reaches the melting point of the solder particles PL contained in the solder paste P more quickly than the surface temperature of the substrate 1 around that land 3.

When the temperature of the land 3 reaches the melting point of the solder particles PL, a molten solder nucleus C is generated on the surface of the land 3, as shown in the middle of FIG. 4. The molten solder nucleus C then grows while attracting the surrounding solder particles PL. At this time, the molten solder nucleus C on the right side of FIG. 4 also attracts the solder particles PL between the adjacent lands 3. Eventually, as shown in the bottom of FIG. 4, substantially all of the solder particles PL, including the solder particles PL around the land 3, melt and gather on the land 3. The control unit 20 then operates the board relay conveyor 232 and the board discharge conveyor 233 to transport the board 1 to the cooling unit 220.

(Cooling process)
In the cooling process, the cooling fan 221 cools the substrate 1 having molten solder on the lands 3. Specifically, the control unit 20 operates the cooling fan 221 to cool the substrate 1 with air flow passing through the air vents 220a and 220b, thereby solidifying the molten solder. In this manner, a solder precoat is formed on the lands 3 of the substrate 1, and the solder precoated substrate is completed. Then, the control unit 20 operates the substrate discharge conveyor 233 to discharge the cooled substrate 1 (solder precoated substrate) from the cooling unit 220.

<Modification of the First Embodiment>
A modified example of the first embodiment of the present disclosure will be described. This modified example differs from the first embodiment in the configuration of the heating unit 210. Below, the differences from the first embodiment will be mainly described.

As shown in FIG. 5, the heating section 210 of this modified example does not include a second heater 212. Therefore, in the heating process of this modified example, the substrate 1 is heated only by the first heater 211. In other words, in the heating process of this modified example, the substrate 1 is heated only from the back side (lower side) of the substrate 1. Note that, even in this modified example, it is preferable to heat the substrate 1 so that the temperature of the surface of the substrate 1 increases at a rate of increase of 4° C./sec or more.

In this way, by not providing the second heater 212, in other words by providing only the first heater 211 as a heat source, it is possible to reduce the cost of the manufacturing apparatus 10 and simplify the structure.

Second Embodiment
A second embodiment of the present disclosure will be described. This embodiment differs from the first embodiment in the configurations of the heating unit 210 and the cooling unit 220. The following mainly describes the differences from the first embodiment.

(Heating section)
As shown in FIGS. 6 and 7 , the heating unit 210 of this embodiment includes a heating plate 214 , a sheet 216 , and a holding unit 217 during heating.

The heating plate 214 heats the substrate 1 by contacting the rear surface (lower surface) of the substrate 1 located in the heating area HA. More specifically, the heating plate 214 heats the substrate 1 only from the rear surface side by generating heat while contacting the wiring pattern 4 of the substrate 1. As a result, as shown in FIG. 7, similar to the first embodiment described above, molten solder nuclei grow on the lands 3 of the substrate 1 due to heating, and eventually, a state is achieved in which molten solder gathers on the lands 3.

The sheet 216 is sandwiched between the substrate 1 and the heating plate 214 when the substrate 1 is heated by the heating plate 214. The sheet 216 is made of a material (e.g., silicon) that is softer than the substrate 1 and the heating plate 214. The sheet 216 is preferably replaced every time a predetermined number of substrates 1 (e.g., one substrate) are replaced by a supply roller 216a that feeds out the sheet 216 and a recovery roller 216b that takes up the sheet 216. In the heating step of this embodiment, the substrate 1 is heated by the heating plate 214 with the sheet 216 sandwiched between the substrate 1 and the heating plate 214.

The heating presser 217 presses the substrate 1 at multiple points (in this example, the four corners of the substrate 1) when the substrate 1 is heated by the heating plate 214. The heating presser 217 has multiple legs 217a that each press the substrate 1, and a frame 217b that connects the multiple legs 217a. The multiple legs 217a and the frame 217b are made of a highly insulating material. In the heating process of this embodiment, the substrate 1 is heated by the heating plate 214 while the substrate 1 is pressed at multiple points by the heating presser 217.

(Cooling section)
As shown in Fig. 6, the cooling section 220 of this embodiment has a cooling press section 222. The cooling press section 222 presses the substrate 1 at multiple locations (in this example, six locations along the opposing sides of the substrate 1) when the substrate 1 is cooled by the cooling fan 221. The cooling press section 222 has multiple lower rollers 222a that contact the back surface of the substrate 1, and multiple upper rollers 222b that sandwich the substrate 1 together with the multiple lower rollers 222a. Each of the lower rollers 222a and each of the upper rollers 222b is made of a highly insulating material. In the cooling step of this embodiment, the substrate 1 is cooled by the cooling fan 221 while the substrate 1 is pressed at multiple locations by the cooling press section 222.

The following describes the embodiment in more detail based on examples and comparative examples. The scope of the present disclosure is not to be construed as being limited by the examples.

Using a heating unit 210, a substrate 1, and a solder paste P configured as shown below, the probability of bridges occurring (hereinafter referred to as the "bridge occurrence rate") for 200 chips was measured for each measurement condition (Comparative Examples 1 and 2 and Examples 1 to 3). In this case, the bridge occurrence rate is a value expressed as (number of bridges occurring/200) x 100 (unit: %).

Specifically, a reflow furnace UNI-6116 manufactured by Antom was used as the heating unit 210. In the heating process, only the first heater 211 was operated, and the second heater 212 was turned off. The set temperatures of the first heater 211 were 230°C (Comparative Example 1), 260°C (Comparative Example 2), 300°C (Example 1), 330°C (Example 2), and 360°C (Example 3).

The substrate 1 used was rectangular, measuring 150 mm x 100 mm, and 0.8 mm thick. The layout of the lands 3 on the substrate 1 was designed to accommodate 0201 chip components mounted with a component-to-component distance of 70 μm.

Furthermore, solder paste type 5 (particle size: 15 to 25 μm) made by Senju Metal was used as the solder paste P.

The measurement results of Comparative Examples 1 and 2 and Examples 1 to 3 are shown in Table 1. Here, the rate of increase is a value expressed as (200-100)/Δt (unit: °C/sec), where Δt (unit: seconds) is the time required for the surface temperature of substrate 1 to increase from 100°C to 200°C.

As can be seen from Table 1, when the rate of increase was 4.00°C/sec or more, the bridging rate was 0%. On the other hand, when the rate of increase was less than 4.00°C/sec, the bridging rate was not 0%, and the occurrence of the bridging phenomenon was confirmed.

This disclosure can be used in manufacturing methods and manufacturing equipment for solder precoated substrates.

1: Substrate 2: Substrate body 3: Land 4: Wiring pattern 10: Manufacturing apparatus for solder precoated substrate 11: Support frame 11a: Linear guide mechanism 11b: Print head moving mechanism 20: Control unit 100: Supply unit 101: Base 102: Moving table 103: Lifting mechanism 104: Print stage 104a: Base 104b: Support 104c: Substrate guide 104d: Side clamper 104e: Backup lifting mechanism 104f: Backup unit 113: Print head 113a: Support beam 113b: Rear squeegee 113c: Front squeegee 113d: Squeegee drive unit 116: Mask plate 210: Heating unit 211: First heater 212: Second heater 213: Housing 214: Heating plate 215: Ventilation hole 216: Sheet 216a: Supply roller 216b: Recovery roller 217: Holding portion during heating 217a: Legs 217b: Frame 220: Cooling portion 220a: Vent 220b: Vent 221: Cooling fan 222: Holding portion during cooling 222a: Lower roller 222b: Upper roller 224: Housing 231: Printing stage conveyor 232: Board relay conveyor 233: Board unloading conveyor 234: Board loading conveyor C: Solder molten core HA: Heating area P: Solder paste PA: Solder paste supply area PL: Solder particle

Claims (14)

A method for manufacturing a solder precoated substrate by forming a solder precoat on a plurality of lands provided on a surface of a substrate, comprising:
a supplying step of supplying solder paste to the plurality of lands;
a heating step of heating the substrate so that a temperature of the lands reaches a melting point of solder particles contained in the solder paste faster than a surface temperature of the substrate around the lands;
a cooling step of cooling and solidifying the molten solder particles to form the solder precoat;
Equipped with
In the heating step, the substrate is heated so that the temperature of the substrate surface increases at a rate of increase of 4° C./sec or more. The method for manufacturing a solder precoated substrate according to claim 1, wherein in the heating step, the substrate is heated more strongly from the back side of the substrate than from the front side of the substrate. The method for manufacturing a solder precoated substrate according to claim 2, wherein the substrate is heated only from the back side of the substrate in the heating step. The method for manufacturing a solder precoated substrate according to any one of claims 1 to 3, wherein in the heating step, the substrate is heated using a heating plate that contacts the rear surface of the substrate. The method for manufacturing a solder precoated substrate according to claim 4, wherein in the heating step, the substrate is heated with a sheet sandwiched between the substrate and the heating plate. The method for manufacturing a solder precoated substrate according to any one of claims 1 to 5, wherein in the heating step, the substrate is heated while being held down at multiple points. The method for manufacturing a solder precoated substrate according to any one of claims 1 to 6 , wherein in the cooling step, the substrate is cooled while being pressed at a plurality of points . An apparatus for manufacturing a solder precoated substrate by forming a solder precoat on a plurality of lands provided on a surface of a substrate, comprising:
A supply unit that supplies solder paste to the lands;
a heating unit that heats the substrate so that a temperature of the lands reaches a melting point of solder particles contained in the solder paste faster than a surface temperature of the substrate around the lands;
a cooling section that cools and solidifies the molten solder particles to form the solder precoat;
Equipped with
The heating section heats the substrate so that the temperature of the substrate surface increases at a rate of increase of 4° C./sec or more. The manufacturing device for solder precoated substrates according to claim 8, wherein the heating unit heats the substrate more strongly from the back side of the substrate than from the front side of the substrate. The manufacturing device for solder precoated substrates according to claim 9, wherein the heating unit heats the substrate only from the rear surface side of the substrate. The manufacturing device for solder precoated substrates according to any one of claims 8 to 10, wherein the heating unit has a heating plate that contacts the rear surface of the substrate to heat the substrate. The manufacturing apparatus for solder precoated substrates according to claim 11, further comprising a sheet that is sandwiched between the substrate and the heating plate when the substrate is heated. The manufacturing device for solder precoated substrates according to any one of claims 8 to 12, further comprising a heating holding unit that holds the substrate at multiple points when the substrate is heated. The manufacturing apparatus for a solder precoated substrate according to any one of claims 8 to 13, further comprising a cooling pressing section that presses the substrate at a plurality of points when the substrate is cooled.

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