JP5589592B2 - Soldering method - Google Patents

Description

  The present invention relates to a soldering method capable of enhancing the durability of an electrical component soldered to a substrate such as a substrate.

  Patent Document 1 discloses a chip resistor in which an alloy protective layer is coated on a resistor layer provided on an insulating substrate, and the alloy protective layer is further coated with a glass protective layer. Patent Document 2 discloses a step of forming an electrode on an upper surface of an insulating substrate having slits for dividing and cutting, a step of forming a resistor so as to overlap the electrode, a step of covering the resistor with a glass layer, and a slit. The manufacturing method of the square chip fixed resistor including the process of dividing | segmenting an insulation board | substrate into many vias is disclosed. Patent Document 3 discloses a step of forming an upper surface electrode layer formed of a gold-based metal thin film on an upper surface of a substrate, a step of providing a NiCr-based resistance layer electrically connected to the upper surface electrode layer, A method for manufacturing a resistor is disclosed in which a step of forming a first protective layer made of resin so as to cover and a step of forming a second protective layer made of resin so as to cover the first protective layer are sequentially performed.

Japanese Patent Laid-Open No. 5-67501 JP-A-1-151204 Japanese Patent Laid-Open No. 11-204304

  The board manufactured by the above-described method has a plurality of electrical components mounted thereon by soldering. When soldering, a flux containing an activator is generally used to remove the oxide film from the molten solder, remove the oxide film from the soldered part, improve the wettability of the molten solder, etc. It is. However, the activator contained in the flux may remain on the substrate after soldering. If the flux contacts the hot molten solder during soldering, the activator contained in the flux is inactivated, so there is no problem.

  However, when the temperature of the solder in contact with the flux is low, the activator of the flux may remain on the substrate in a state where the inactivation of the activator contained in the flux is not promoted. In this case, if the substrate is used in an environment with high humidity that generates condensed water, such as for automobiles or the like, or if the substrate is used in an environment where external water enters, the activity remaining on the substrate There is a possibility that components contained in the agent may mix with water and generate corrosive ionic water. In this case, it may become a factor that a crack is generated on the joint surface between the protective coating layer covering the electrical component for waterproofing and moistureproofing and the substrate. In this way, the ionic water is a factor that damages and peels off the protective coating layer. As a result, it may become a factor for promoting the deterioration of the solder part and the electrical parts. In particular, when the component contained in the activator of the flux is a halogen element (eg, Br, Cl), the ionic water exhibits corrosiveness and causes the protective coating layer to be peeled off, resulting in deterioration of the solder part and electrical parts. It may become a factor to promote.

  In recent years, since lead-free solder is often used so as not to contain lead, the activity of the activator contained in the flux tends to be higher for improving the solderability. In this case, the corrosivity of ionic water tends to be improved.

  The present invention has been made in view of the above-described circumstances, and suppresses damage to the protective coat layer due to the active agent remaining on the substrate such as a substrate after soldering, thereby improving the durability of the protective coat layer. It is an object of the present invention to provide a soldering method that is advantageous for improving and extending the service life.

The soldering method according to the present invention includes: (i) a first solder that solders a first electrical component to a first region of a base via a solder layer laminated on a conductive layer provided on the base having electrical insulation. (Ii) Thereafter, the second electrical component is soldered in a state where the flux containing the activator is present in a second region different from the first region where the first electrical component is soldered in the base. (Iii) Thereafter, the base body to which the first electric component and the second electric component are soldered is set at the lower limit temperature Tmin of (a) and the upper limit temperature Tmax of (b) below. A heat treatment step for reducing the influence of the activator contained in the flux by heating in the region of the heat treatment temperature set within the specified range ; and
After the heat treatment step, performing a coating step of covering the first electrical component soldered to the base with a protective coating layer,
It said substrate and / or the protective coating layer is a soldering method for have a flow-contacting suppressing structure to suppress that the fluids to be attached to the substrate in contact with the junction surface between the protective coating layer and the substrate.
(A) Lower limit temperature Tmin of heat treatment temperature: 180 ° C. or higher (b) Upper limit temperature of heat treatment temperature Tmax: Temperature obtained by adding margin value α (0 to 10 ° C.) to solder melting temperature is defined as T1. The temperature on the lower side of the temperature T1 and the temperature T2 when the heat resistant temperature of the electric component on the lower heat resistant temperature side of the two electric components is T2 .
Here, the solder melting temperature can be grasped as a liquidus line in the solder state diagram. The reason why the solder melting temperature is used as the upper limit temperature Tmax of the heat treatment temperature is that when the heat treatment temperature is excessively high, the solder portion soldering the first electric component and the second electric component is excessively melted, This is because the first electrical component and the second electrical component may be displaced from their home positions. In the first soldering step, the first electrical component is soldered to the first region of the base via a solder layer laminated on the upper surface of the conductive layer of the base having electrical insulation. In this case, in order to improve solderability, it is preferable to employ a flux containing an activator.

  In the second soldering step, the second electric component is soldered in a state where the flux containing the activator is present in a second region different from the first region where the first electric component is soldered in the base. The flux improves the surface tension of the molten solder and improves the wettability of the solder. The activator contained in the flux serves to remove the melted oxide film of the solder, the oxide film of the conductive layer of the substrate, and the like, thereby improving the solderability of the electrical component such as the second electrical component. The activator generally contains a halogen compound and also contains an organic acid and / or an inorganic acid.

In the heat treatment step, the influence of the activator contained in the flux is reduced by heating the substrate on which the first electric component and the second electric component are soldered in the above temperature range. In this case, the activity of the halogen element contained in the flux activator is reduced by the heat treatment.
(A) Lower temperature limit Tmin of heat treatment temperature in heat treatment step: 180 ° C. or higher (b) Upper temperature limit Tmax of heat treatment temperature: temperature T1 obtained by adding margin value α (0-10 ° C.) to solder melting temperature, first electrical component, and When the heat resistant temperature of the electric component on the lower heat resistant temperature side of the second electric component is T, the lower temperature temperature T1 of the temperature T1 and the temperature T2 is set to the margin value α (0 To 10 ° C.). The margin value α takes into account factors such as the time required for heat transfer and the heat treatment process time. When the time of the heat treatment process is short, the margin value α is preferably increased within the range of 0 to 10 ° C. because the influence on the electrical components is small. When the time of the heat treatment step is long, it is preferable to reduce the margin value α within the range of 0 to 10 ° C. About the heat-resistant temperature T2 of an electrical component, it is set as the heat-resistant temperature of the side with the low heat-resistant temperature of a 1st electrical component and a 2nd electrical component. This is to improve the protection of the first electric component and the second electric component in the heat treatment process.

  According to the present invention, in the heat treatment step, the activator contained in the flux (especially the activator) is obtained by heating the base body to which the first electric component and the second electric component are soldered in the above temperature range. (Halogen element contained in) is reduced. For this reason, the occurrence of cracks due to the activator is suppressed during use after soldering. In particular, when a protective coating layer for covering an electrical component is formed, the occurrence of cracks at the joint surface between the protective coating layer and the substrate is suppressed. Therefore, it is advantageous for improving the durability and extending the life of the solder part and the electrical component.

It is a figure which concerns on Embodiment 1 and shows a manufacturing process. It is a graph which shows the relationship between the temperature of heat processing, and the amount of ions. It is a graph which shows the relationship between the amount of ions and the crack occurrence rate. FIG. 10 is a perspective view showing a state where an electrical component soldered on a substrate is covered with a protective coat layer according to the second embodiment. FIG. 5 is a cross-sectional view showing a state according to the second embodiment, cut along the Y direction of FIG. 4. FIG. 5 is a cross-sectional view showing the state according to the second embodiment by cutting along the X direction of FIG. 4. FIG. 10 is a perspective view showing a state where an electrical component soldered on a substrate is covered with a protective coat layer according to the third embodiment. FIG. 8 is a cross-sectional view showing a state according to the third embodiment by cutting along the X direction of FIG. 7. FIG. 8 is a cross-sectional view showing a state according to the third embodiment, cut along the Y direction of FIG. 7. FIG. 9 is a cross-sectional view of a state where an electrical component soldered on a substrate is covered with a protective coating layer according to the fourth embodiment. FIG. 10 is a cross-sectional view of a state where an electrical component soldered on a substrate is covered with a protective coating layer according to the fifth embodiment.

  Any substrate may be used as long as an electrical component can be mounted thereon. The substrate can be a plate-like substrate, but is not limited to a plate shape. The electrical component includes an electronic component. The heat treatment time maintained in the heat treatment temperature region in the heat treatment step is preferably within 180 seconds. This is to increase the productivity of the heat treatment process in order to avoid the influence of heat on the electrical components. Further, even if the heat treatment temperature is maintained for a longer time, the improvement effect by the heat treatment is saturated. Although it varies depending on the heat treatment temperature, the time for heating to the heat treatment temperature is generally preferably within 120 seconds, within 60 seconds, or within 30 seconds. In general, the higher the heat treatment temperature, the shorter the heat treatment time.

  Preferably, in the second soldering step, the lower surface of the base is brought close to or in contact with the molten solder in the solder bath in a state where the base is disposed on the upper side of the solder bath storing the molten solder, It is performed by supplying the surface side. Preferably, the base body has a through hole penetrating the base body in the thickness direction. In the second soldering step, the lower surface of the base body is placed in the solder tank while the base body is disposed above the solder tank storing the molten solder. The molten solder is brought close to or in contact with the molten solder, and the molten solder is supplied to the upper surface side of the substrate through the through hole. Although it does not specifically limit as a melting temperature (liquidus) of solder, 150-310 degreeC and 170-280 degreeC are illustrated.

  Depending on the application of the first electric component or the second electric component mounted on the substrate, components such as an activator contained in the flux remaining on the substrate may exist in the substrate as corrosive ionic water. . Further, when the activator remains on the substrate, condensed water in which moisture contained in the atmosphere is condensed may dissolve components such as the activator, and may exist in the substrate as corrosive ionic water. Therefore, the heat treatment step described above is performed to promote inactivation of the activator contained in the flux.

  Moreover, it is preferable that the coating | coated process which coat | covers the 1st electrical component soldered to the base | substrate with a protective coating layer after a heat treatment process is implemented. The protective coat can be formed of an inorganic material and / or a resin material. Examples of the inorganic material include ceramics such as alumina, alumina nitride, and silicon carbide. Examples of the resin material include a thermosetting resin and a thermoplastic resin. As the thermosetting resin, alkyd resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin and the like can be used. Examples of the thermoplastic resin include acrylic resin, polystyrene resin, polyamide resin, fluorine resin, polypropylene resin, polyvinyl acetate resin, methacrylic resin, and urethane resin. Natural resin rosin and / or modified rosin can also be used.

  Furthermore, it is preferable that the substrate and / or the protective coat layer have a fluid contact suppressing structure that suppresses the contact of the fluid attached to the substrate with the bonding surface between the protective coat layer and the substrate. It is preferable that the fluid contact suppression structure includes a downflow inclined surface that is formed on the upper surface of the substrate and allows the fluid present on the substrate to flow down. The fluid contact suppression structure preferably has a groove formed on the upper surface of the substrate to prevent the fluid existing on the substrate from coming into contact with the bonding surface between the protective coat layer and the substrate. Moreover, it is preferable that a fluid contact-inhibition structure has a rosin coating layer that covers the outside of the protective coating layer.

(Embodiment 1)
Hereinafter, an embodiment of the present invention will be described with reference to FIG. In the soldering method according to the present embodiment, in the first soldering step, as shown as the state (1) in FIG. 1, a substrate 1 having a base material made of an electrically insulating ceramic (for example, alumina or silicon carbide). In the first region 1f of the upper surface 1u that is the surface of the (base), the conductive layer 11 formed of a conductive material such as copper is formed as an electrode layer. Further, as shown as the state (2) in FIG. 1, the solder layer 2 is laminated on the upper surface of the conductive layer 11 on the substrate 1 by printing. Next, as shown as a state (3) in FIG. 1, the first electrical component 31 is disposed on the solder layer 2 on the substrate 1. The outer wall surface of the first electrical component 31 has a metal thin film 31c for improving solderability. As shown in the state (4) of FIG. 1, in this state, the substrate 1 is inserted into a heating furnace, the solder layer 2 is heated in the atmosphere to melt and solidify the solder layer 2, and the first electric component 31 is attached to the substrate. Soldering to the first region 1f of one. The solder layer 2 is filled. The first electrical component 31 is a component that uses electricity, and may be an electrical component or an electronic component, and examples include a resistor, a capacitor, a coil, a microcomputer, a memory, an interface, an input device, and an output device. The first electrical component 31 may be one in which an electronic element such as a resistor is mounted on an insulating substrate.

  Thereafter, a second soldering process is performed. In the second soldering step, as shown as the state (5) in FIG. 1, the second region different from the first region 1f in which the first electric component 31 is soldered in the substrate 1 with the substrate 1 turned upside down. A flux 4 containing an activator containing a halogen element is applied and present in the region 1s (lower position inverted up and down). The flux 4 includes an activator containing a halogen element (for example, Br, Cl).

  With the flux 4 applied, the second electrical component 32 is placed on the lower surface 1d (the surface that is on the upper side by inversion) of the substrate 1 as shown in state (6) in FIG. Here, the board | substrate 1 has the through hole 13 which is a through hole which penetrates this in the thickness direction. The through hole 13 is provided with a through hole conductive layer 11m made of a conductive material such as copper. The through-hole conductive layer 11m includes a cylindrical portion 110 coated on the inner peripheral wall surface of the through-hole 13, a conductive flange portion 112 serving as a first flange portion coated on one side of the substrate 1, and the substrate 1 It has the electroconductive collar part 114 as the 2nd collar part coat | covered on the other side. Legs 32 c serving as terminals of the second electrical component 32 are inserted into the through holes 13 so as to face the cylindrical portion 110.

  In the second soldering step, as shown in the state (7) of FIG. 1, the substrate 1 is brought close to the hot water surface 5s side of the solder bath 5, also called a Dip bath, in which the molten solder 50 (temperature: 300 to 440 ° C.) is stored. Let them be arranged. In this state, the operating source 52 provided in the solder bath 5 is operated, and a part of the molten solder 50 in the solder bath 5 is partially lifted toward the upper surface 1d on the lower side of the substrate 1. As a result, the raised molten solder 50 penetrates and penetrates through the through hole 13 together with a part of the flux 4 toward the second electric component 32 while contacting the through hole conductive layer 11m in the through hole 13 of the substrate 1. . This molten solder is disposed between the flange portion 112 of the conductive layer 11 m of the substrate 1 and the lower surface 32 d of the second electrical component 32. If the molten solder supplied through the through hole 13 of the substrate 1 is solidified, the second electric component 32 is the first of the substrates 1 with the legs 32c of the second electric component 32 inserted into the through hole 13. It is soldered and fixed to the side opposite to the electrical component 31. At this time, the molten solder in the through hole 13 also quickly solidifies, and the leg 32c of the second electrical component 32 is fixed in the through hole 13 of the substrate 1.

  Thereafter, the substrate 1 on which the first electrical component 31 and the second electrical component 32 are soldered is placed in a furnace chamber in an atmosphere of the heat treatment furnace 6 to perform a heat treatment process. Here, in the heat treatment step, the temperature Tmin on the lower limit temperature side of the heat treatment temperature is set to 180 ° C. or higher. In particular, 190 ° C or higher, 195 ° C or higher, and 200 ° C or higher are preferable. The temperature Tmax on the upper limit temperature side of the heat treatment temperature is less than the solder melting temperature + α. It is preferable to set α appropriately within a range of 0 to 10 ° C. and within a range of 0 to 5 ° C. depending on the solder material. However, it is preferable to consider the heat resistant temperature T2 of the electric component having the lower heat resistant temperature of the first electric component 31 and the second electric component 32. Therefore, the temperature Tmax on the upper limit temperature side of the heat treatment temperature can be either the temperature T1 lower than the solder melting temperature + α or the temperature T2 lower than the heat resistance temperature of the electrical component. Therefore, the lower one of the temperature T1 and the temperature T2 is adopted as the temperature Tmax on the upper limit temperature side. The heat treatment time can be within 180 seconds, within 120 seconds, within 60 seconds, or within 30 seconds. If the heat treatment time is excessively long, the electrical components 31 and 32 may be affected, and the heat treatment productivity decreases. If the heat treatment time is excessively short, heat transfer becomes insufficient, and the inactivation of the activator contained in the flux may be reduced.

  By such a heat treatment step, the influence of the activator (particularly halogen elements such as Br and Cl) contained in the flux is reduced. In this case, the activator (particularly halogen element) contained in the flux is inactivated. As a mechanism for inactivation by heat treatment, it is presumed that the active component of the activator (particularly a halogen element) forms a compound with other components constituting the flux in a high temperature atmosphere and is inactivated. There is no problem even if the inactive active agent remains. Thereafter, after the heat treatment step, a covering step of covering the first electric component 31 and / or the second electric component 32 soldered to the substrate 1 with a protective coating layer is performed. The protective coat layer may be a resin coat, an inorganic coat, or a combination of both.

  As described above, according to the present embodiment, the substrate 1 on which the first electric component 31 and the second electric component 32 are soldered is heated in the heat treatment temperature region described above in the heat treatment step. For this reason, even when the activator contained in the flux used in the second soldering process remains on the substrate 1, the activator (particularly halogen element) remaining on the substrate 1 is inactivated. It can be promoted in the heat treatment step. For this reason, in the protective coat layer which coat | covers the 1st electrical component 31 and / or the 2nd electrical component 32, it is suppressed that damages, such as a crack, resulting from an activator (especially halogen element) generate | occur | produce.

  That is, when the activator contained in the flux comes into contact with the high-temperature molten solder, the activator contained in the flux is inactivated by the heat of the molten solder. However, in the present embodiment, in the second soldering step, the molten solder lifted to the substrate 1 side is on the lower side of the substrate 1 due to surface tension or the like while being in contact with the flux 4 existing on the substrate 1. The upper surface 1u (surface) may flow toward the first electrical component 31 along the direction of arrow E (the state shown in (6) of FIG. 1). Such a temperature of the molten solder considerably reduces the temperature. When the solder whose temperature has been lowered in this manner flows along the surface of the substrate 1 while being in contact with the flux 4 of the substrate 1, even if the activator contained in the flux 4 comes into contact with the molten solder, the molten solder 50 Since the temperature is low, the activator is not easily inactivated. Therefore, the activator may remain on the upper surface 1u (the surface on which the first electrical component 31 is mounted) of the substrate 1 while maintaining the active state. When the activator that has not been deactivated as described above remains on the upper surface 1u (the surface on which the first electrical component 31 is mounted) of the substrate 1, the following problems may occur.

  That is, when the substrate 1 is installed in an environment where the humidity is high enough to generate condensed water, such as in-vehicle, or when the substrate 1 is installed in an environment where external water enters, the substrate 1 is used. Ingredients contained in the activator remaining in the water (insufficiently inactivated) may be mixed with water to produce corrosive ionic water. In this case, the ionized water causes the protective coat layer on the substrate 1 to be peeled off, and may cause the deterioration of the solder part and the electrical component covered with the protective coat layer. In particular, when the component contained in the flux activator is a halogen element such as Br or Cl, the ionic water exhibits corrosivity. In this case, the ionized water causes damage such as peeling to the protective coat layer and the like, and may promote deterioration of the solder part and the electrical parts.

  In this regard, according to the present embodiment, the substrate 1 to which the first electric component 31 and the second electric component 32 are soldered is heated in the heat treatment temperature region described above in the heat treatment step. For this reason, even when the activated activator contained in the flux 4 used in the second soldering process remains on the substrate 1, the upper surface 1 u (the first electric component 31 of the substrate 1). Inactivation of the activator (especially halogen element) remaining on the mounted surface) can be promoted in the heat treatment step. For this reason, in the protective coat layer covering the first electrical component 31 and / or the second electrical component 32, occurrence of damage such as cracks due to the activator (particularly halogen element) is suppressed. Therefore, it is possible to improve the durability and extend the life of the substrate 1 on which the first electrical component 31 and the second electrical component 32 are mounted.

  Note that a flux containing an activator is also used in the first soldering step. However, in the first soldering step, since the temperature of the molten solder that comes into contact with the flux is as high as 180 ° C. or more or 200 ° C. or more, the activator contained in the flux is inactivated. Therefore, the flux remaining in the first soldering process is not particularly troublesome. In addition, a well-known solder can be employ | adopted as solder used in a 1st soldering process and a 2nd soldering process, for example, Sn type | system | group, Sn-Ag type | system | group, Sn-Ag-Cu type | system | group, Depending on the case, the Sn-Pb system is exemplified.

(Example of actual machine test)
A test for confirming the effect of the first embodiment was performed as an actual machine test example. In this case, as the first soldering step, the electrical component 31 is made using a solder paste containing a solder paste and a flux (melting temperature: 210 to 220 ° C., model: TLF-204-SIS, Tamura Corporation). Was soldered to the substrate 1. Next, the electrical component 32 was soldered using the flux 4 in the second soldering step. (Electrical component 32 is soldered in the second soldering step.) The composition of the solder was Sn-3.0 mass% Ag-0.5 mass% Cu. The flux 4 used was a post flux (model: ES-1061, Senju Metal Co., Ltd.) containing an activator containing a halogen element (Br). If the substrate 1 is actually used over a long period of time in a humid atmosphere where there is a possibility of generating condensed water, cracks occur at the bonding surface between the protective coating layer made of resin and the substrate, and the protective coating layer is peeled off. Tended to occur. Furthermore, there was a tendency for Ag migration to occur under the peeled protective coat.

(Model test example)
In the case of the actual machine test, a long-term test of one year or more was required. Therefore, an accelerated test was performed by simulating the state of water and conducting the following model test. A model test piece (Panasonic Corporation, 1608 size (product number: 961010-45200, model number: ERJ3GEYJ104V)) was used, and an acceleration test was performed according to (i) to (iv).
(I) A post flux (model: ES-1061, Senju Metal Co., Ltd.) containing an activator containing a halogen element (Br) subjected to heat treatment was mixed with pure water. Thereby, a plurality of mixed waters in which the amount of ions (Br ions) was changed within the range of 0 to 1400 ppm was formed. After each mixed water was allowed to stand for 2 days or longer, the supernatant was collected as a test solution. A test solution with a low ion content was prepared by diluting with pure water.
(Ii) Twenty chip resistors were immersed as test pieces in a test solution (temperature: room temperature (25 ° C.)) formed from the supernatant, and left in a thermostatic bath for 2 weeks. Twenty chip resistors were immersed in each test solution adjusted to each concentration.
(Iii) Each test piece was taken out from each test solution, and the test piece was ultrasonically cleaned with a solvent (IPA) (10 minutes × 2 times). Furthermore, the test piece was dried at 60 ° C. for 1 hour.
(Iv) Optical microscope observation and electron microscope observation (SEM) were performed to detect cracks in the test piece. The crack occurrence rate was measured. Cracks were formed on the joint surface between the protective coat layer and the upper surface of the substrate.

  2 and 3 show the test results. The horizontal axis in FIG. 2 indicates the heat treatment temperature, and the vertical axis indicates the amount of ions (Br ions) in the test solution. The amount of ions was measured by gas chromatography. The horizontal axis in FIG. 3 indicates the amount of ions (Br ions), and the vertical axis indicates the crack generation rate in the test piece. 2 and 3, the A range is a preferred range, and the B range is a more preferred range. According to FIG. 2, the amount of ions decreases as the heat treatment temperature increases. In particular, when the heat treatment temperature is 180 ° C. or higher and 190 ° C. or higher, the amount of ions is significantly reduced. When the heat treatment temperature was 200 ° C., the amount of remaining ions was about 100 ppm, and when the heat treatment temperature was 250 ° C., it was substantially zero.

  According to FIG. 3, the crack generation rate in the test piece decreases as the ion amount decreases. In particular, in the accelerated test, if the ion content is 200 ppm, the crack generation rate is reduced to about 10%. Since this is an accelerated test, even 10% is considered to be satisfactory under practical use conditions. If the amount of ions is 100 ppm, the crack generation rate is reduced to 0%. Based on the test results shown in FIGS. 2 and 3, the heat treatment temperature is preferably 180 ° C. or higher, particularly 190 ° C. or higher, particularly 200 ° C. or higher in order to reduce the amount of ions.

(Embodiment 2)
4 to 6 show a first electrical component 31 according to the second embodiment. FIG. 4 is a perspective view of the first electric component 31. FIG. 5 shows a longitudinal section cut along the Y direction. FIG. 6 shows a cross section cut along the X direction. This embodiment has basically the same configuration and the same operation and effect as the first embodiment. The first electric component 31 has an insulating substrate 31a formed of ceramics or the like. The insulating substrate 31a is formed with a substrate exposed surface 31au on one side (upper surface in the illustration of FIG. 4) side from which the material of the insulating substrate 31a is exposed, and a substrate exposed surface 31ad on the other surface (lower surface in the illustration of FIG. 4) side. Yes. The insulating substrate 31a is covered with a metal thin film 31c. The metal thin film 31c is covered with a plating layer formed of copper, tin, or an alloy thereof.

Also in the present embodiment, as in the first embodiment, after the second soldering step is performed, the substrate 1 on which the first electric component 31 and the second electric component 32 are soldered is set to the lower limit temperature of (a) below. By heating in the temperature range set within the range of the upper limit temperature Tmax of Tmin, (b), the influence by the activator contained in the flux 4, especially the influence by the halogen element contained in the activator is reduced. A heat treatment step is performed. The heat treatment time varies depending on the flux 4 used, but is preferably within 180 seconds, within 120 seconds, and within 60 seconds.
(A) Lower limit temperature Tmin of heat treatment temperature: 180 ° C. or higher,
(B) Upper limit temperature Tmax of the heat treatment temperature: T1 is a temperature obtained by adding the margin value α (0 to 10 ° C.) to the solder melting temperature, and the heat resistance temperature side of the first electric component 31 and the second electric component 32 is lower When the heat-resistant temperature of the electrical component is T2, the temperature on the lower side of the temperatures T1 and T2 and, after the heat treatment step, the first electrical component 31 soldered on the substrate 1 is covered with the protective coat layer 7 A coating process has been carried out. As shown in FIG. 5, the protective coat layer 7 includes an inorganic coat layer 71 based on ceramics that covers the resistor 31 b (electronic element) of the first electrical component 31, and thermosetting that covers the inorganic coat layer 71. And a resin coat layer 72 having a base material made of an adhesive resin (for example, epoxy resin, phenol resin, etc.). In some cases, the inorganic coat layer 71 may be a resin coat layer. In FIG. 5, the resin coat layer 72 covers the resistor 31 b which is the main element of the first electric component 31. In FIG. 6, the resin coat layer 72 covers the upper surface of the insulating substrate 31a. The second electrical component 32 may or may not be covered with a protective coating layer. In FIG. 6, a lower surface 72d indicates the lower surface (end surface) of the resin coat layer 42, and 72x indicates a bonding surface between the resin coat layer 72 and the insulating substrate 1a.

(Embodiment 3)
7 to 9 show the third embodiment. FIG. 7 shows a perspective view of the first electrical component 31. FIG. 8 shows a longitudinal section cut along the X direction. FIG. 9 shows a cross section cut along the Y direction. This embodiment basically has the same configuration and the same function and effect as the first and second embodiments. The first electrical component 31 has an insulating substrate 31a formed of ceramic having electrical insulation. The surface of the insulating substrate 31a is covered with a metal thin film 31c, which is a conductive layer that forms an electrode layer. The metal thin film 31c is covered with a plating layer formed of copper, tin, or an alloy thereof.

Also in the present embodiment, as in the first and second embodiments, the substrate 1 on which the first electrical component 31 and the second electrical component 32 are soldered is subjected to the following lower limit temperature Tmin (a) and upper limit temperature (b). By performing heating in a temperature range set within the range of Tmax, a heat treatment step is performed to reduce the influence of the activator contained in the flux, particularly the influence of the halogen element contained in the activator.
(A) Lower limit temperature Tmin of heat treatment temperature: 180 ° C. or higher,
(B) Upper limit temperature Tmax of the heat treatment temperature: T1 is a temperature obtained by adding the margin value α (0 to 10 ° C.) to the solder melting temperature, and the heat resistance temperature side of the first electric component 31 and the second electric component 32 is lower When the heat-resistant temperature of the electrical component is T2, the lower temperature of the temperatures T1 and T2 By such a heat treatment step, the activator contained in the flux becomes inactive and has corrosive properties during use. Production of ionic water is suppressed. According to the present embodiment, after the heat treatment step, as shown in FIGS. 8 and 9, the resistor 31 b (electronic element) of the first electric component 31 soldered on the substrate 1 is covered with the protective coat layer 7 from the outside. A coating process for coating is performed. The protective coat layer 7 includes an inorganic coat layer 71 based on alumina or the like that covers the resistor 31b (electronic element) from the outside, and a thermosetting resin (such as an epoxy resin or a phenol resin) that covers the inorganic coat layer 71. ) As a base material. In some cases, the inorganic coat layer 71 may be a resin coat layer.

  In the present embodiment, as shown in FIGS. 7 to 9, the upper surface is opened by irradiating the substrate exposed surface 31au of the insulating substrate 31a before the first soldering process with a high energy density beam such as a laser beam or an electron beam. The first groove 101 is formed in a straight shape, and the second groove 102 intersecting the first groove 101 is formed in a straight shape so as to communicate with the middle portion in the length direction of the first groove 101. As shown in FIG. 7, the first grooves 101 have an upper surface opening 101u and are arranged in parallel so as to sandwich the resin coat layer 72 from both sides. The second groove 102 has an upper surface opening 102u opened upward and a side surface opening 102d opened laterally. The second groove 102 communicates with the first groove 101 and supplies water (a fluid such as ionic water) to the insulating substrate. It can discharge to the outer side of 31a. For example, the groove width of the first groove 101 and the second groove 102 can be 10 to 50 micrometers and the groove height can be 20 to 70 micrometers, but is not limited thereto.

  As shown in FIGS. 7 and 8, the first groove 101 is not covered with the resin coat layer 72 and is located on both sides of the resin coat layer 72 and insulated from the lower surface 72 d (end surface) of the resin coat layer 72. Adjacent to the entrance side of the joint surface 72x with the upper surface of the substrate 31a (the outer edge 72p side where the side surface 72s of the resin coat layer 72 intersects the substrate exposed surface 31au which is the upper surface of the insulating substrate 31a). . For this reason, corrosive ion water (fluid) is prevented from entering the bonding surface 72x between the lower surface 72d of the resin coat layer 72 and the upper surface of the insulating substrate 31a. The first groove 101 and the second groove 102 are formed on the upper surface of the insulating substrate 31a in a region other than the metal thin film 31c (the substrate exposed surface 31au where the substrate material on the upper surface of the insulating substrate 31a is exposed). This is because the metal thin film 31 c is formed on the upper surface of the insulating substrate 31 a so that the metal thin film 31 c does not contact the first groove 101 and the second groove 102. In the first groove 101 and the second groove 102, fluid such as ionic water that adheres to the substrate 1 or the insulating substrate 31a contacts the bonding surface 72x between the lower surface 72d of the resin coat layer 72 and the upper surface of the insulating substrate 31a. It can function as a fluid contact suppression structure that suppresses this.

  As described above, according to the present embodiment, in the manufacturing stage, the heat treatment process is performed so that the activator (particularly, halogen element) of the flux 4 does not remain on the mounting substrate 1. For this reason, even when there is a possibility that water may be applied to the substrate 1 depending on the use of the mounting component, or when moisture in the atmosphere condenses and becomes condensed water in the substrate 1, the water is corrosive. Generation of ionic water is suppressed. Therefore, the durability of the substrate 1 can be enhanced.

  However, ionic water (fluid) having corrosivity may be present in the substrate 1 due to some circumstances (for example, intrusion from the outside). Even in such a case, according to the present embodiment, since the first groove 101 and the second groove 102 are formed on the upper surface of the insulating substrate 31a of the first electrical component 31, the ionic water is used for the first electrical Damage to the component 31 is suppressed. Therefore, it is possible to suppress the occurrence of cracks due to ionic water on the bonding surface 72x between the lower surface 72d (end surface) of the resin coat layer 72 and the upper surface (front surface) of the insulating substrate 31a. This can contribute to improving the durability and extending the life of the resin coat layer 72, and thus contributing to improving the durability and extending the life of the first electrical component 31.

(Embodiment 4)
FIG. 10 shows a fourth embodiment. FIG. 10 shows a cross section cut along the X direction. This embodiment basically has the same configuration and the same function and effect as the first and second embodiments. The present embodiment has basically the same configuration and the same function and effect as each embodiment. Also in the present embodiment, as in each embodiment, the substrate 1 to which the first electrical component 31 or the like is soldered is set within the ranges of the following lower limit temperature Tmin (a) and upper limit temperature Tmax (b). A heat treatment step for reducing the influence of the activator contained in the flux is carried out by heating in the above temperature range.
(A) Lower limit temperature Tmin of heat treatment temperature: 180 ° C. or higher (b) Upper limit temperature of heat treatment temperature Tmax: Temperature obtained by adding margin value α (0 to 10 ° C.) to solder melting temperature is defined as T1, and the first electrical component 31 and When the heat-resistant temperature of the electric component on the lower heat-resistant temperature side of the second electric component 32 is T2, the temperature on the lower side of the temperatures T1 and T2 By such a heat treatment step, the activator contained in the flux Becomes inactive, and the production of corrosive ionic water is suppressed.

  Then, after the heat treatment step, a covering step of covering the resistor 31b (electronic element) of the first electric component 31 with the protective coating layer 7 (see FIG. 10) is performed. The protective coat layer 7 includes an inorganic coat layer 71 based on ceramics covering the resistor 31b, and a resin coat layer 72 based on a thermosetting resin (eg, epoxy resin) covering the inorganic coat layer 71. It is formed with. In some cases, the inorganic coat layer 71 may be a resin coat layer.

  According to the present embodiment, as shown in FIG. 10, the upper surface of the insulating substrate 31a along the horizontal surface is formed at the end of the insulating substrate 31a by cutting or polishing, or by a high energy density beam such as a laser beam. In contrast, a downflow inclined surface 200 that is inclined downward at an inclination angle θ (see FIG. 10) is formed. As shown in FIG. 10, the downflow inclined surface 200 includes a straight first downflow inclined surface 201 and a second downflow inclined surface 202 formed at positions facing each other. As shown in FIG. 10, the downflow inclined surfaces 201 and 202 are directed outward with the outer edge 72xp of the joint surface 72x between the lower surface 72d of the resin coat layer 72 of the protective coat layer 7 and the upper surface of the insulating substrate 31a substantially as a starting point. It is extended so as to incline downward. Ends 201e and 202e of the downflow inclined surfaces 201 and 202 are inclined downward so as to reach the side surface 31s of the ceramic insulating substrate 31a. Such downflow inclined surfaces 201 and 202 direct the water as the fluid present on the upper surfaces of the protective coat layer 7 and the insulating substrate 31a toward the outside of the insulating substrate 31a (side surface 31s of the insulating substrate 31a), and the arrow A2 It has the function of flowing down along the direction to escape. For this reason, even if water (corrosive ionic water or non-ionic water) is present on the resin coat layer 72 of the protective coat layer 7 or the upper surface of the insulating substrate 31a, the water is allowed to escape. It is possible to suppress the accumulation of water (fluid).

  As described above, according to the present embodiment, as in each of the above-described embodiments, the flux activator (particularly halogen element) that may remain on the substrate 1 is not activated in the substrate 1 in the manufacturing stage. A heat treatment step is performed. For this reason, even when there is a possibility that water may be applied to the substrate 1 depending on the use of the first electrical component 31 or the like, or even when moisture in the atmosphere is condensed and becomes condensed water in the substrate 1, the water is corroded. It is water with little property, and it becomes suppressed that it becomes corrosive ionic water. Therefore, the durability of the mounting substrate 1 can be enhanced.

  However, even if ionic water having corrosiveness is present on the insulating substrate 31a or the resin coat layer 72 of the electrical component 31 for some reason (for example, intrusion from the outside), as shown in FIG. In addition, a first downflow inclined surface 201 and a second downflow inclined surface 202 are formed on the upper surface of the insulating substrate 31a. For this reason, corrosive ionic water (fluid) can escape from the upper surface of the insulating substrate 31a through the descending inclined surfaces 201 and 202. Therefore, water can be prevented from entering the resin coat layer 72 from the bonding surface 72x between the lower surface 72d of the resin coat layer 72 and the upper surface of the insulating substrate 31. Therefore, it is suppressed that corrosive ion water damages the resin coat layer 72, the inorganic coat layer 71, the solder part, the 1st electric component 31, etc., and can improve these durability. Accordingly, in the first downflow inclined surface 201 and the second downflow inclined surface 202, a fluid such as ionic water that adheres to the substrate 1 contacts the bonding surface 72x between the lower surface 72d that is the end surface of the resin coat layer 72 and the insulating substrate 31a. It can function as a fluid contact suppression structure that suppresses this.

(Embodiment 5)
FIG. 11 shows a fifth embodiment. FIG. 11 shows a cross section cut along the X direction. This embodiment basically has the same configuration and the same function and effect as the first and second embodiments. Also in the present embodiment, after the soldering process is completed, the substrate 1 on which the first electrical component 31 or the like is soldered is set within the following ranges of the lower limit temperature Tmin of (a) and the upper limit temperature Tmax of (b). A heat treatment step for reducing the influence of the activator contained in the flux is performed by heating in the temperature range.
(In this embodiment as well, in the same manner as in the first embodiment, the temperature range in which the substrate 1 after the soldering process has been set is set within the range of the lower limit temperature Tmin of (a) and the upper limit temperature Tmax of (b) below. A heat treatment step for reducing the influence of the activator contained in the flux is performed by heating inside.
(A) Lower limit temperature Tmin of heat treatment temperature: 180 ° C. or higher (b) Upper limit temperature of heat treatment temperature Tmax: Temperature obtained by adding margin value α (0 to 10 ° C.) to solder melting temperature is defined as T1, and the first electrical component 31 and When the heat-resistant temperature of the electric component on the lower heat-resistant temperature side of the second electric component 32 is T2, the temperature on the lower side of the temperatures T1 and T2 And, after the heat treatment step, the first electric component 31 is protected A coating step of coating with layer 7 is carried out. As shown in FIG. 11, the protective coat layer 7 is formed of an inorganic coat layer 71 that covers the resistor 31 b (electronic element) of the first electrical component 31 and a resin material such as an epoxy resin that covers the inorganic coat layer 71. The resin coating layer 72 is formed. Further, as shown in FIG. 11, rosin (natural resin, matsuya) is applied by an application means such as a spray so as to cover the joint surface 72x between the upper surface of the insulating substrate 31a and the lower surface 72d of the resin coat layer 72 from the outside. Covering. As a result, the rosin coating layer 78 is coated on the outside of the resin coat layer 72. The lower surface 78d of the rosin coating layer 78 covers the upper surface of the insulating substrate 31a from above. Further, a lower end portion 78s extending downward from the rosin coating layer 78 covers the side surface 31s of the insulating substrate 31a from the outside.

  As described above, according to the present embodiment, in the manufacturing stage, the heat treatment process is performed so that the activator (particularly, halogen element) of the flux 4 does not remain on the mounting substrate 1. For this reason, the activator of the flux becomes inactive, and the production of corrosive ionic water is suppressed. Therefore, even when water may be applied to the substrate 1 depending on the use of the electrical components 31 and 32, or even when moisture in the atmosphere condenses to become condensed water in the substrate 1, the water is corrosive. As a result, it is suppressed that the water becomes corrosive ionic water. Therefore, the possibility that the resin coat layer 72 is damaged by corrosive ionic water (fluid) is suppressed. Therefore, the durability of the first electrical component 31, the second electrical component 32, and the solder portion on the substrate 1 can be enhanced.

  However, there is a possibility that corrosive ionic water exists on the substrate 1 or the protective coat layer 7 due to some circumstances (for example, intrusion from the outside). Even in such a case, the resin coating layer 72 is covered with the rosin coating layer 78 so as to cover the side surface 72s thereof. For this reason, corrosive ion water is prevented from entering the resin coat layer 72 from the bonding surface 72x between the lower surface 72d (end surface) of the resin coat layer 72 and the insulating substrate 31a. Therefore, it is suppressed that corrosive ion water damages the resin coat layer 72, the 1st electrical component 31, and a solder part. Therefore, the rosin coating layer 78 is a fluid contact suppression structure that suppresses the contact of the fluid such as ionic water attached to the substrate 1 with the bonding surface 72x between the lower surface 72d of the resin coat layer 72 and the upper surface of the insulating substrate 31a. Can function.

(Other)
In the embodiment shown in FIG. 1, the second electrical component 32 is soldered to the surface opposite to the first electrical component 31 in order to increase the mounting density of the electrical components. May be soldered to the surface on the same side as the first electrical component 31. The electric component includes an electronic component. The present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within the scope not departing from the gist. A fluid contact suppression structure such as a groove or a descending slope is not necessarily formed on the substrate 1 or the like. In the second soldering step, the substrate 1 may be brought into contact with the flat molten metal surface of the molten solder 50 in the solder bath 5 without particularly lifting the molten metal surface of the molten solder 50 in the solder bath 5. The following technical idea can also be grasped from this specification.
[Additional Item 1] A base such as a substrate having electrical insulation, an electrical component soldered via a solder layer laminated on a conductive layer provided in the first region of the base, and soldering to the base The substrate and / or the protective coating layer is such that the fluid adhering to the substrate contacts the bonding surface between the protective coating layer and the substrate. A base soldering structure having a fluid contact suppressing structure that suppresses the occurrence of the above. In this case, damage to the protective coat layer due to fluid such as ionic water having corrosiveness is suppressed. Although it is preferable to perform the above-mentioned heat treatment step before coating the protective coating layer, it is not necessary to perform it.
[Additional Item 2] The substrate soldering structure according to Additional Item 1, wherein the fluid contact suppression structure includes a downflow inclined surface that is formed on an upper surface of the substrate and allows the fluid existing on the substrate to flow down. Although it is preferable to carry out the above-described heat treatment step, it is not necessary to carry out it. It is preferable that the downflow inclined surface flows down from the protective coat layer to the outside of the protective coat layer.
[Additional Item 3] In Additional Item 1, the fluid contact suppression structure is formed on the upper surface (surface) of the substrate, and the fluid existing on the substrate contacts the bonding surface between the protective coat layer and the substrate. A base soldering structure having a groove that suppresses this. In this case, damage to the protective coat layer due to a fluid such as corrosive ionic water is suppressed. Although it is preferable to carry out the above-described heat treatment step, it is not necessary to carry out it. The groove is preferably provided outside the bonding surface in the base.
[Additional Item 4] In Additional Item 1, the fluid contact suppression structure is a base soldering structure having a rosin coating layer that covers an outer side of the protective coating layer. In this case, damage to the protective coat layer due to a fluid such as corrosive ionic water is suppressed. Although it is preferable to carry out the above-described heat treatment step, it is not necessary to carry out it.
[Additional Item 5] In one of Additional Items 1 to 4, the base body has a through hole penetrating the base body in the thickness direction, and the soldering step is performed above the solder tank storing the molten solder. In the state where the base is disposed, the base solder is performed by bringing the lower surface of the base closer to or in contact with the molten solder in the solder bath and supplying the molten solder to the upper surface side of the base through the through hole. Attached structure.

  1 is a substrate (base), 1u is an upper surface (surface), 1d is a lower surface (surface), 11 is a conductive layer, 2 is a solder layer, 31 is a first electrical component, 31a is an insulating substrate, 32 is a second electrical component, 5 is a solder bath, 50 is molten solder, 6 is a heat treatment furnace, 7 is a protective coating layer, 71 is an inorganic coating layer, 72 is a resin coating layer, 72x is a bonding surface, 78 is a rosin coating layer (fluid contact inhibition structure) , 101 and 102 are grooves (fluid contact suppression structure), 200 is a downward slope, 201 is a first downward slope, and 202 is a second downward slope (fluid contact suppression structure).

Claims (6)

A first soldering step of soldering the first electrical component to the first region of the base via a solder layer laminated on a conductive layer provided on the base having electrical insulation;
Thereafter, a second solder for soldering the second electrical component in a state where a flux containing an activator is present in a second region different from the first region to which the first electrical component is soldered of the base. Attaching process,
Thereafter, the base body to which the first electric component and the second electric component are soldered is within the region of the heat treatment temperature defined by the following lower limit temperature Tmin of (a) and upper limit temperature Tmax of (b). And heat treatment step to reduce the influence of the active agent contained in the flux by heating in ,
After the heat treatment step, performing a coating step of covering the first electrical component soldered to the base with a protective coating layer,
It said substrate and / or the protective coating layer is a soldering method for have a flow-contacting suppressing structure to suppress that the fluids to be attached to the substrate in contact with the junction surface between the protective coating layer and the substrate.
(A) Lower limit temperature Tmin of heat treatment temperature: 180 ° C. or higher,
(B) Upper limit temperature Tmax of heat treatment temperature: T1 is a temperature obtained by adding a margin value α (0 to 10 ° C.) to the solder melting temperature, and the heat resistance temperature side of the first electric component and the second electric component is lower When the heat-resistant temperature of the electrical component is T2, the lower temperature of the temperature T1 and the temperature T2   2. The soldering method according to claim 1, wherein the heat treatment time maintained in the heat treatment temperature region in the heat treatment step is within 180 seconds.   3. The second soldering step according to claim 1, wherein the second soldering step brings the lower surface of the base close to the molten solder in the solder tank with the base disposed on the upper side of the solder tank storing the molten solder. Or the soldering method performed by making it contact and supplying the said molten solder to the surface side of the said base | substrate. In one of claims 1 to 3, wherein the flow animal contact inhibition structure, soldering method has a flow down the inclined surface to flow down the fluids that are formed on the upper surface of the substrate present in the substrate. 4. The fluid contact suppression structure according to claim 1, wherein the fluid contact suppression structure is formed on an upper surface of the substrate, and the fluid existing on the substrate contacts a bonding surface between the protective coat layer and the substrate. A soldering method having a groove for suppressing this. In one of claims 1 to 3, wherein the flow animal contact inhibition structure, soldering method having the rosin coating layer covering the outside of the protective coating layer.

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