JP6370110B2 - Method for manufacturing solder joint structure, solder joint structure, and solder joint method - Google Patents

Description

  The present invention relates to a method for manufacturing a solder joint structure in which a circuit board and an electronic component or the like are soldered together, a solder joint structure manufactured thereby, and a solder joint method. More specifically, the present invention relates to a solder joint structure and a solder joint method capable of suppressing the progress of cracks occurring in a flux residue and a solder joint even when placed in a thermal shock cycle environment where the difference between the temperature and the heat is particularly severe.

  Conventionally, as a method for joining an electronic component to a circuit board, a method is generally used in which a solder paste mixed with solder powder and flux is printed on the circuit board, and the electronic component is mounted and then heated to be joined. It is used for. The flux removes the metal oxide on the surface of the solder and the circuit board while preventing reoxidation of the metal at the time of soldering and lowering the solder surface tension. It is indispensable for good soldering. is there. However, when solder bonding is performed using a solder paste, most of the flux remains as a residue on the circuit board after the solder bonding is completed. For example, when an electronic component is mounted on a circuit board having an electrode part and an insulating layer using a solder paste and soldering is to be performed, the flux component leaches out during the soldering process, and the electronic component and the insulating layer The flux residue is localized between the two.

Such a flux residue has a problem that cracks are likely to occur due to its properties. In particular, in the case of a circuit board that is placed in an environment where there is a difference in temperature when used, the flux residue that has been subjected to severe thermal shock is particularly susceptible to cracking. Then, moisture penetrates into the circuit portion of the circuit board through the cracks, causing a problem that the circuit is short-circuited or the metal of the circuit is corroded.
In addition, in the case of a circuit board placed in an environment with a temperature difference, a large stress is generated in the solder joint due to a difference in coefficient of linear expansion between the mounted electronic component and the circuit board. A crack is generated in the solder joint due to repeated plastic deformation of the solder joint due to the stress. Furthermore, in the process where stress is repeatedly applied over time, the stress concentrates on the solder near the crack tip, and the crack extends to a deeper portion of the solder joint. Thus, when a crack progresses remarkably, there exists a problem that the electrical connection of an electronic component and a circuit board will be impaired finally.
Until now, solder joints have been performed well in a relatively mild environment, although there is a difference in temperature as in the interior of an automobile. However, in recent years, for example, the temperature difference between the engine in the engine room, the direct mounting of the engine, and the motor / electrical power integration with the motor is particularly severe (temperature difference between −40 ° C. to 125 ° C. and −40 ° C. to 150 ° C.), and vibrations are also generated. Examination and practical application of circuit board arrangement in such a harsh environment have been made. Under such a harsher environment, there is a problem that both the flux residue and the solder joint cannot exhibit a sufficient crack suppressing effect. It is expected that there will be an increasing demand for fluxes and solder pastes that are capable of exhibiting sufficient performance in a harsh environment in which such a temperature difference is very large and vibrations are applied.

As a solder joint structure that suppresses the occurrence of cracks in the flux residue and the solder joint, it is formed using a flux containing an acrylic resin having a glass transition point of −40 ° C. or lower or a softening temperature of the flux residue or higher, and from −40 ° C. A solder joint structure having a flux residue whose maximum coefficient of linear expansion in the temperature range up to the softening temperature of the flux residue is 300 × 10 ⁻⁶ / K or less is disclosed (see Patent Document 1). For the purpose of improving solder joint strength, an electronic component device is disclosed in which a soldering flux is interposed between an electronic component and a component mounting board, and the two are bonded together (see Patent Document 2).

  The solder joint structure disclosed in Patent Document 1 maintains the solder joint strength of the solder joint structure by preventing a decrease in solder strength at the time of temperature change from a high temperature to a low temperature. However, once a crack occurs in the flux residue or solder joint, it is difficult to disperse the stress concentrated near the crack tip and to suppress the progress of the crack in the above structure.

  In addition, the electronic component device disclosed in Patent Document 2 is not premised on being placed in an environment where there is a great difference in temperature as described above, and it is difficult to suppress the progress of cracks in such an environment. Furthermore, in the design of the pattern, if the vicinity of the solder joint on the circuit board is concave, or if the size of the electronic component to be mounted is large and the volume between the circuit board, the electronic component, and the solder joint is large, it is supplied onto the electrode part. The flux contained in the solder paste alone cannot form a sufficient flux residue to fill the space between the circuit board, the electronic component, and the solder joint, which makes it difficult to suppress the flux residue and the crack growth occurring in the solder joint. There is also a problem.

International Publication No. 2009/104693 JP 2001-170798 A

  The present invention solves the above-mentioned problems, and exhibits excellent adhesive force even in an environment where the temperature difference between -40 ° C. and 150 ° C. is severe and the thermal shock is large, especially during use. Provided are a method for manufacturing a solder joint structure that can suppress the progress of cracks that occur and prevent a decrease in the solder shear strength of the solder joint structure, and a solder joint structure manufactured thereby and a solder joint method That is the purpose.

The method for manufacturing a solder joint structure according to the present invention includes a paste supplying step of supplying a solder paste containing flux onto an electrode portion provided on a circuit board, a mounting step of mounting an electronic component on the circuit substrate, and the electronic component A reflow process for forming a solder joint and a flux residue by reflowing the circuit board on which the circuit board is mounted. Before the mounting process, a pattern provided on the circuit board and the electrode part are supplied. In accordance with the component and amount of the flux contained in the solder paste, the flux is supplied to a predetermined region other than the electrode portion, which is a region facing the electronic component at the time of soldering on the circuit board. The flux remaining from the flux that oozes from the solder paste and / or the flux Is formed so as to be interposed between and bonded to at least the circuit board or an insulating layer provided on the circuit board, the electronic component, and the solder joint, and is -40 ° C / 30 minutes to 150 ° C / The adhesive strength of the flux residue after 2000 cycles of a thermal shock test with 30 minutes as one cycle is 3.5 N / mm ² or more, and at least one of the flux and the flux contained in the solder paste is synthesized. It is characterized by containing a resin, a thixotropic agent, an activator, and a solvent.

(2) In the configuration of (1) above, the flux and the flux contained in the solder paste may have either the same composition or different compositions.

(3) In the configuration of (1) or (2), the synthetic resin is acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic acid, anhydrous Acrylic resin obtained by polymerizing at least one monomer of maleic acid, maleic acid ester, maleic anhydride ester, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl chloride vinyl acetate, rosin resin having carboxyl group And a dimer acid derivative flexible alcohol compound and a derivative compound obtained by dehydration condensation, and at least one selected from the group of epoxy resins, phenol resins, and rosin resins.

(4) In any one of the constitutions (1) to (3), in the paste supplying step, the flux is supplied to the predetermined region simultaneously with the supply of the solder paste onto the electrode portion. It is characterized by that.

(5) The solder joint structure of the present invention is produced by the method for producing a solder joint structure having any one of the constitutions (1) to (4), and is applied to the solder joint structure from −40 ° C./30 minutes to It is characterized in that the rate of decrease in the solder shear strength is 50% or less before and after 2000 cycles of the thermal shock test with 150 ° C./30 minutes as one cycle.

(6) The solder bonding method of the present invention includes a step of supplying a solder paste containing flux on an electrode portion provided on a circuit board, a step of mounting an electronic component on the circuit substrate, and the mounting of the electronic component. A step of reflowing the circuit board to form a solder joint and soldering the circuit board to the electronic component, and the electronic component is provided on the circuit board before mounting on the circuit board. Depending on the pattern to be formed and the component and amount of the flux contained in the solder paste supplied onto the electrode part, a predetermined area other than the electrode part is a region facing the electronic component at the time of soldering on the circuit board. Flux is supplied to the region, and is shaped by at least one of the flux that exudes from the solder paste and the flux in the reflow process. The flux residue is formed so as to be bonded to and interposed between at least the circuit board or the insulating layer provided on the circuit board, the electronic component, and the solder joint, and -40 ° C / 30 minutes. The adhesive force of the flux residue after giving 2000 cycles of a thermal shock test with a cycle of ˜150 ° C./30 minutes is 3.5 N / mm ² or more, and at least of the flux and the flux contained in the solder paste One is characterized by containing a synthetic resin, a thixotropic agent, an activator, and a solvent.

In the method for manufacturing a solder joint structure, the solder joint structure, and the solder joint method of the present invention, the flux residue formed by at least one of the flux that exudes from the solder paste and the flux according to the shape of the pattern. The circuit board, the insulating layer, the electronic component, and the solder joint may be interposed between the circuit board, the insulating layer, the electronic component, and the solder joint.
Further, the flux residue contained in the solder joint structure is not only between the circuit board, the insulating layer, the electronic component, and the solder joint, but also on the surface of the solder joint and at least a part of the circuit board. And a part of the electronic component may be formed.

According to the method for manufacturing a solder joint structure of the present invention, it is excellent even if it is placed in a harsh environment where there is a great difference in temperature between heating and cooling, without going through complicated steps and regardless of the pattern of the circuit board or the type of electronic component. The flux residue exhibiting the adhesive force can be formed to sufficiently adhere to at least the circuit board or the insulating layer formed on the circuit board, the electronic component, and the solder joint.
The flux is supplied to a predetermined region on the substrate according to a pattern or the like provided on the circuit substrate. Therefore, for example, when the amount of flux contained in the solder paste is sufficient to form the flux residue having the above-described configuration, it is possible to select an optimal operation as appropriate, such as not supplying the flux.

  The solder joint structure having such a configuration is easy to disperse stress concentrated near the crack tip even when a crack occurs in the solder joint, and suppresses the progress of the crack and is excellent. Demonstrates solderability and prevents a decrease in solder shear strength.

  According to another aspect of the method for producing a solder joint structure of the present invention, the flux contained in the solder paste and the flux may have either the same composition or different compositions, thereby reducing the work burden. Can do.

  Further, according to the solder joint structure of the present invention, the solder joint structure is subjected to a thermal shock test in which one cycle is −40 ° C./30 minutes to 150 ° C./30 minutes before and after giving 2000 cycles. A reduction rate of strength can be reduced to 50% or less, and a highly reliable circuit board is provided even when it is left for a long time in a harsh environment where the difference between the temperature and the temperature is severe and the vibration is strong. It becomes possible.

  Furthermore, according to the soldering method of the present invention, even if a crack occurs in the solder joint, the stress concentrated near the crack tip is easily dispersed, and the progress of the crack is suppressed and an excellent solder is obtained. It becomes possible to perform solder joint that exhibits jointability and prevents a decrease in solder shear strength.

  Therefore, according to the method for manufacturing a solder joint structure of the present invention, the solder joint structure, and the solder joint method, even in an environment exposed to a long-term severe thermal shock cycle and vibration, for example, in an automobile engine room, A circuit board capable of maintaining sufficient bonding reliability can be provided.

The fragmentary sectional view showing a manufacturing process concerning one embodiment of a manufacturing method of a solder joint structure of the present invention. The fragmentary sectional view showing a manufacturing process concerning other embodiments of a manufacturing method of a solder joint structure of the present invention. The graph showing the flux residue adhesive strength in the thermal shock test which concerns on one Example and one comparative example of the soldering structure of this invention, and makes -40 to 125 degreeC 1 cycle. The graph which represented the shear strength of the solder joint structure in the thermal shock test which concerns on the Example and the comparative example of the solder joint structure of this invention, and makes -40 degreeC-125 degreeC 1 cycle. According to the same example and comparative example of the solder joint structure of the present invention, a cross-sectional photograph of a chip resistor (solder joint structure) after 2000 cycles of a thermal shock test with −40 ° C. to 125 ° C. as one cycle . The graph which represented the flux residue adhesive strength in the thermal shock test which concerns on the same Example and the comparative example of the soldering structure of this invention, and makes -40 degreeC-150 degreeC 1 cycle. The graph showing the shear strength of the solder joint structure in the thermal shock test which concerns on the Example and the comparative example of the solder joint structure of this invention, and makes -40 degreeC-150 degreeC 1 cycle. According to the same example and comparative example of the solder joint structure of the present invention, a cross-sectional photograph of a chip resistor (solder joint structure) after 2000 cycles of a thermal shock test with −40 ° C. to 150 ° C. as one cycle .

  One embodiment of a flux and a flux (hereinafter collectively referred to as “the present flux”) contained in a solder paste used in the method for producing a solder joint structure of the present invention will be described in detail below. Note that the flux and flux contained in the solder paste may have the same composition or different compositions.

<Flux>
1. Synthetic Resin A synthetic resin can be used for the flux of the present embodiment. Examples of such synthetic resins include acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, esters of maleic acid, and maleic anhydride. Dehydration of acrylic resin obtained by polymerizing at least one monomer of ester, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl chloride and vinyl acetate, rosin resin having carboxyl group and dimer acid derivative flexible alcohol compound Derivative compounds formed by condensation are exemplified. These can be used alone or in combination.

  Among the acrylic resins, acrylic resins obtained by polymerizing methacrylic acid and monomers containing two saturated alkyl groups having 2 to 20 carbon atoms in which the carbon chain is linear are preferably used.

  In addition, as the rosin resin having a carboxyl group used for a derivative compound obtained by dehydrating condensation of the rosin resin having a carboxyl group and a dimer acid derivative flexible alcohol compound (hereinafter referred to as “rosin derivative compound”), For example, rosins such as tall oil rosin, gum rosin, wood rosin; hydrogenated rosin, polymerized rosin, heterogeneous rosin, rosin derivatives such as acrylic acid modified rosin, maleic acid modified rosin, etc. Any rosin can be used. These can be used alone or in combination.

  Next, examples of the dimer acid derivative flexible alcohol compound include compounds derived from dimer acid such as dimer diol, polyester polyol, and polyester dimer diol, and those having an alcohol group at the terminal thereof. For example, PRIPOL 2033, PRIPLAST 3197, PRIPLAST 1838 (manufactured by Croda Japan Co., Ltd.) and the like can be used.

  The rosin derivative compound is obtained by dehydrating and condensing the rosin resin having a carboxyl group and the dimer acid derivative flexible alcohol compound. As the dehydration condensation method, a generally used method can be used. Moreover, the preferable weight ratio at the time of carrying out dehydration condensation of the rosin-type resin which has the said carboxyl group, and the said dimer acid derivative flexible alcohol compound is 25: 75-75: 25, respectively.

  The acid value of the synthetic resin is preferably 10 to 150 mgKOH / g, and the blending amount thereof is 10% by weight with respect to the total amount of flux to be generated (both flux and flux contained in the solder paste; the same applies hereinafter). % To 90% by weight is preferred.

2. Thixotropic agent A thixotropic agent can be used for this flux of this embodiment. Examples of such thixotropic agents include, but are not limited to, hydrogenated castor oil, fatty acid amides, and oxy fatty acids.
The blending amount of such a thixotropic agent is preferably 3% by weight to 15% by weight with respect to the total amount of flux to be generated.

3. Activator An activator can be used for this flux of this embodiment. As such an activator, for example, an amine salt (inorganic acid salt or organic acid salt) such as an organic amine hydrogen halide salt, an organic acid, an organic acid salt, or an organic amine salt can be blended. More specifically, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salt, acid salt, succinic acid, adipic acid, sebacic acid and the like can be mentioned. These can be used alone or in combination.
The blending amount of such an activator is preferably 5% by weight to 15% by weight with respect to the total amount of generated flux.

4). Solvent A solvent can be used for this flux of this embodiment. As such a solvent, for example, isopropyl alcohol, ethanol, acetone, toluene, xylene, ethyl acetate, ethyl cellosolve, butyl cellosolve, glycol ether and the like can be used. These can be used alone or in combination.
The blending amount of such a solvent is preferably 20% by weight to 40% by weight with respect to the total amount of generated flux.

5. Antioxidant Antioxidant can be used for this flux of this embodiment. Examples of such antioxidants include hindered phenolic antioxidants, phenolic antioxidants, bisphenolic antioxidants, and polymer-type antioxidants. Of these, hindered phenol-based oxidizing agents are particularly preferably used, but usable antioxidants are not limited to these. These can be used alone or in combination.
The blending amount of such an antioxidant is not particularly limited, but generally it is preferably about 0.5 to 5% by weight with respect to the total amount of flux to be generated.

6). Rosin Resin A rosin resin can be used for the flux of the present embodiment. Examples of such rosin resins include rosin such as tall oil rosin, gum rosin, and wood rosin, and rosin polymerization, hydrogenation, heterogeneity, acrylation, maleation, esterification, and phenol addition reaction. The performed rosin-modified resin or the like can be used. These can be used alone or in combination.
The blending amount of such a rosin resin is preferably 20% by weight or less based on the total amount of flux to be generated.

  You may add additives, such as acrylic resin and a halogen, a delustering agent, and an antifoamer, to this flux of this embodiment further.

  As such an acrylic resin, for example, a resin made of a polymer having an acrylic monomer as a polymerization component can be used. Examples of such acrylic monomers include acrylic acid having an acidic group, methacrylic acid, acrylic ester having an ester group, and methacrylic ester. In addition, a resin made of a polymer using only these acrylic monomers can also be used. The blending amount of such an acrylic resin is preferably 50% by weight or less with respect to the total amount of flux to be generated.

  Moreover, it is preferable that the compounding quantity of the said additive is 10 weight% or less with respect to the flux whole quantity to produce | generate. Moreover, these further preferable compounding quantities are 5 weight% or less with respect to the total amount of the flux to produce | generate.

The flux residue formed by heating the flux of the present embodiment has an adhesive strength after applying a thermal shock test with 2000 cycles of −40 ° C./30 minutes to 150 ° C./30 minutes as one cycle. It can be kept at 5 N / mm ² or more.
The adhesive force of the flux residue can be adjusted as appropriate depending on the acid value and glass transition temperature of the resin component blended in the flux.

<Solder paste>
The solder paste of this embodiment can be obtained by mixing the above flux component and solder powder.
There is no restriction | limiting in particular as said solder alloy powder, For example, Sn, Ag, Cu, Bi, Zn, In, Ga, Sb, Au, Pd, Ge, Ni, Cr, Al, P, In, Pb etc. were combined together. General-purpose ones such as those can be used. As typical solder alloy powder, Sn—Pb solder alloy powder containing Sn and Pb, and lead-free solder alloy powder such as Sn—Ag—Cu and Sn—Ag—Cu—In can be used.

  Among the above solder alloy powders, Sn-Sb, Sn-Sb-Ag, Sn-Sb-Bi, Sn-Sb-In, Sn-Sb-Ag-Bi, Sn-Sb-Ag-In, Sn-Sb-Bi -In, Sn-Ab-Ag-Bi-In, Sn-Ag, Sn-Cu, Sn-Bi, Sn-Ag-Cu, Sn-Ag-Bi, Sn-Cu-Bi, Sn-Ag-Cu-Bi In addition, Sn—Pb solder alloy powder is preferably used. These alloy powders can be used alone or in combination.

The amount of the solder alloy powder is preferably 65% by weight or more and 95% by weight or less based on the total amount of the solder paste. A more preferable blending amount is 85% by weight or more and 93% by weight or less, and a particularly preferable blending amount is 89% by weight or more and 92% by weight or less.
When the blending amount of the solder alloy powder is less than 65% by weight, there is a tendency that sufficient solder joints are hardly formed when the obtained solder paste is used. On the other hand, when the content of the solder alloy powder exceeds 95% by weight, the flux component as a binder is insufficient, and it tends to be difficult to mix the flux component and the solder alloy powder.

<Solder joint structure>
An embodiment of a method for producing a solder joint structure of the present invention will be described with reference to FIG.

  In this embodiment, first, the insulating layer 2 and the electrode part 3 are formed on the substrate 1 so as to have a predetermined pattern. As shown in FIG. 1A, in the present embodiment, a pattern is formed such that the space between the insulating layer 2 and the electrode portion 3 is concave, that is, the insulating layer 2 is not provided around part of the electrode portion 3. .

  A solder paste 4 is supplied onto the electrode portion 3 of the substrate 1 on which the pattern is formed (see FIG. 1B). The solder paste 4 is prepared by mixing the flux component and the solder alloy powder. Examples of the method for supplying the solder paste 4 include printing by a printing machine, application by a dispenser, application by spraying, and the like. Any supply method may be adopted as long as the solder paste 4 can be supplied onto the electrode part 3.

Next, on the substrate 1, the flux 5 is supplied to a region opposite to the electronic component 6 when the electronic component 6 is mounted and other than the electrode unit 3. The flux 5 is prepared by mixing the above flux components. In the present embodiment, a predetermined amount of flux 5 is supplied onto the insulating layer 2 provided between the electrode portions 3 (see FIG. 1C). Examples of the method for supplying the flux 5 include printing by a printing machine and application by a dispenser. Any supply method may be adopted as long as the flux can be supplied to the region on the substrate 1.
The supply amount of the flux 5 is appropriately adjusted according to the volume of the space surrounded by the substrate 1, the insulating layer 2, the electrode portion 3, the electronic component 6 and the solder joint portion 8 when the electronic component 6 is soldered onto the substrate 1. The
In this embodiment, the flux 5 is supplied onto the insulating layer 2. However, when the volume of the space is small, the substrate 1 may be reflowed without supplying the flux 5.
Further, in the present embodiment, the flux 5 is supplied to the predetermined area after the solder paste 4 is supplied onto the electrode portion 3. However, the flux 5 may be supplied simultaneously with the supply of the solder paste 4.

  The electronic component 6 is mounted on the substrate 1. In the present embodiment, the electronic component 6 is mounted so that the external electrode 7 of the electronic component 6 is positioned on the solder paste 4 (see FIG. 1D).

  Then, by reflowing the substrate 1 on which the electronic component 6 is mounted, a solder joint portion 8 is formed from the solder paste 4, and the electrode portion 3 and the external electrode 7 of the electronic component 6 are electrically connected via the solder joint portion 8. To be joined. In addition, the flux which oozes out from the solder paste 4 and the flux 5 by the reflow process is interposed between the substrate 1, the insulating layer 2, the electrode part 3, the electronic component 6 and the solder joint part 8. Residue 9 is formed. The flux residue 9 is also formed so as to cover the substrate 1, the electrode portion 3, the solder joint portion 8, and the end portion 10 of the electronic component 6 in a region different from the above region (see FIG. 1 (e)). ). In the case of the pattern formed on the substrate 1 in the present embodiment, the substrate 1, the insulating layer 2, the electrode portion 3, the electronic component 6 and the solder can be obtained only with the flux contained in the solder paste 4 supplied to the electrode portion 3 above. It is considered difficult to form the flux residue 9 that is interposed between the joints 8 and adheres them.

Further, the flux residue 9 has an adhesive strength of 3.5 N / mm ² or more after 2000 cycles of a thermal shock test in which -40 ° C./30 minutes to 150 ° C./30 minutes is one cycle.

  As described above, the solder joint structure 100 manufactured using the manufacturing method of the present embodiment is interposed between the substrate 1, the insulating layer 2, the electrode part 3, the electronic component 6, and the solder joint part 8 as described above. A flux having excellent adhesive force that adheres to any of these and covers the substrate 1, the electrode part 3, the solder joint part 8, and the end part 10 of the electronic component 6 in a region different from the above region. Has residue 9. Thereby, the board | substrate 1, the insulating layer 2, the electrode part 3, the electronic component 6, and the solder junction part 8 can be firmly adhere | attached through the flux residue 9. FIG. Therefore, the flux residue 9 can maintain a sufficient adhesive force even when subjected to severe thermal shock, and even if a crack occurs in the flux residue 9 or the solder joint 8, The concentrated stress is further easily dispersed, and the progress of the crack can be suppressed.

  Furthermore, when the rate of decrease in the solder shear strength of the solder joint 8 before and after applying the thermal shock test can be maintained at 50% or less, it is possible to suppress the progress of the crack over a longer period of time. It becomes.

Further, according to the present embodiment, the amount of the flux 5 is appropriately adjusted by the pattern formed on the substrate 1 and the volume of the space surrounded by the substrate 1, the insulating layer 2, the electrode portion 3, the electronic component 6 and the solder joint portion 8. Therefore, the solder joint structure 100 having the above-described configuration can be obtained without going through an extra step or complicated work and regardless of the type of pattern.
In addition, although the method of respond | corresponding to various patterns by increasing the compounding quantity of the flux contained in the solder paste 4 is also considered, the increase in the compounding quantity of the flux contained in the solder paste 4 inhibits the printability of the solder paste 4. Since it becomes a factor, it is not preferable.

  Next, another embodiment of the method for producing a solder joint structure of the present invention will be described with reference to FIG.

  In the other embodiment, first, the insulating layer 12 and the electrode portion 13 are formed at predetermined positions on the substrate 11. In this embodiment, in order to mount a slightly larger electronic component 16, the electrode portions 13 are provided slightly apart from each other as shown in FIG.

  The solder paste 14 is supplied onto the electrode portion 13 provided on the substrate 11 (see FIG. 2B). Examples of the supply method include printing by a printing press, application by a dispenser, application by spraying, and the like. Any supply method may be adopted as long as the solder paste 14 can be supplied onto the electrode portion 13.

Next, on the substrate 11, the flux 15 is supplied to a region opposite to the electronic component 16 when the electronic component 16 is mounted and other than the electrode portion 13. In this other embodiment, a predetermined amount of flux 15 is supplied onto the insulating layer 12 provided between the electrode portions 13 (see FIG. 2C). Examples of the method for supplying the flux 15 include printing by a printing machine and application by a dispenser. As long as the flux can be supplied to the region on the substrate 11, any supply method may be adopted.
The supply amount of the flux 15 is appropriately adjusted according to the volume of the space surrounded by the insulating layer 12, the electronic component 16, and the solder joint portion 18 when the electronic component 16 is soldered onto the substrate 11.
Furthermore, in this other embodiment, the flux 15 is supplied to the predetermined area after supplying the solder paste 14 onto the electrode portion 13. However, the flux 15 may be supplied simultaneously with the supply of the solder paste 14.

  The electronic component 16 is mounted on the substrate 11. In the other embodiment, the electronic component 16 is mounted such that the external electrode 17 of the electronic component 16 is positioned on the solder paste 14 (see FIG. 1D).

Then, by reflowing the substrate 11 on which the electronic component 16 is mounted, a solder joint portion 18 is formed from the solder paste 14, and the electrode portion 13 and the external electrode 17 of the electronic component 16 are electrically connected via the solder joint portion 8. To be joined. Further, by the reflow process, a flux residue 19 that is interposed between the insulating layer 12, the electronic component 16, and the solder joint portion 18 and adheres to any of these from the flux and the flux 15 that exudes from the solder paste 14 is formed. The flux residue 19 is also formed so as to cover the insulating layer 12, the solder joint 18 and the end 20 of the electronic component 16 in a region different from the above region (see FIG. 2E).
In the case of the pattern formed on the substrate 11 in the present embodiment, only the flux contained in the solder paste 14 supplied onto the electrode 13 is interposed between the insulating layer 12, the electronic component 16 and the solder joint 18. In addition, it is considered difficult to form the flux residue 19 that bonds them.

The flux residue 19 has an adhesive strength of 3.5 N / mm ² or more after 2000 cycles of a thermal shock test in which -40 ° C./30 minutes to 150 ° C./30 minutes is one cycle.

  As described above, the solder joint structure 200 manufactured by using the manufacturing method of this other embodiment is interposed between the insulating layer 12, the electronic component 16, and the solder joint 18 as described above. And a flux residue 19 having an excellent adhesive force that covers the substrate 11, the solder joint portion 18, and the end portion 20 of the electronic component 16 in a region different from the above region. Thereby, the insulating layer 12, the electronic component 16, and the solder joint portion 18 can be firmly bonded via the flux residue 19. Therefore, the flux residue 19 can maintain a sufficient adhesive force even when subjected to severe thermal shock, and even when a crack occurs in the flux residue 19 or the solder joint 18, the flux residue 19 is near the crack tip. The concentrated stress is further easily dispersed, and the progress of the crack can be suppressed.

  Furthermore, when the rate of decrease in the solder shear strength of the solder joint 18 before and after applying the thermal shock test can be kept below 50%, it is possible to suppress the development of the crack over a longer period of time. It becomes.

Further, according to the other embodiment, the amount of the flux 15 is appropriately set even when the volume of the space surrounded by the insulating layer 12, the electronic component 16, and the solder joint portion 18 changes depending on the size of the electronic component 16. Since it can be adjusted, the solder joint structure 200 having the above-described configuration can be obtained without going through an extra step or complicated work and regardless of the size of the electronic component 16.
In addition, although the method of respond | corresponding to various patterns by increasing the compounding quantity of the flux contained in the solder paste 14 is also considered, the increase in the compounding quantity of the flux contained in the solder paste 14 inhibits the printability of the solder paste 14. Since it becomes a factor, it is not preferable.

  The type of electronic component mounted on the circuit board of the present embodiment and other embodiments is not particularly limited, but the effect can be particularly exerted when mounting a chip-type component such as a chip capacitor or a chip LED. .

  Moreover, in this specification, the adhesive force of the said flux residue is measured with the following measuring methods.

A chip component is surface-mounted on a substrate using a flux or a solder paste using the flux, and a flux residue is formed on the substrate. The flux residue is formed so as to adhere to both the chip component and the substrate.
Then, 2000 cycles of the thermal shock test which makes -40 degreeC / 30 minutes-150 degreeC / 30 minutes 1 cycle to the said board | substrate using a thermal shock test apparatus etc. are given.

  Then, the adhesive strength of the flux residue on the substrate after the thermal shock test is measured using an autograph or the like. The measurement conditions conform to JIS standard C60068-2-21. The jig used for measurement is a shear jig having a flat end face and a width equal to or greater than the part dimensions. In the measurement, the shear jig is abutted against the side of the chip part after the thermal shock test and a force parallel to the substrate is applied at a predetermined shear rate to obtain the maximum test force, and this value is calculated as the area of the chip part. Divide by to calculate the adhesive strength of the flux residue. At this time, the shear height is ¼ or less of the component height, and the shear rate is 5 mm / min.

  Furthermore, in this specification, the solder shear strength of the said solder joint part and its decreasing rate are measured with the following measuring methods.

A chip component is surface-mounted on a substrate using a solder paste, and a solder joint and a flux residue are formed on the substrate. The solder shear strength of the board on which the chip component is mounted is measured using an autograph or the like.
Then, 2000 cycles of the thermal shock test which makes -40 degrees C / 30 minutes-155 degrees C / 30 minutes 1 cycle to the said board | substrate using a thermal shock test apparatus etc. are given.
Next, the solder shear strength of the solder joint on the substrate after the thermal shock test is measured using an autograph or the like.
The conditions for measuring the solder shear strength before and after the thermal shock test conform to JIS C60068-2-21. The jig used for measurement is a shear jig having a flat end face and a width equal to or greater than the part dimensions. In the measurement, the shear jig is abutted against the chip component side surface of the substrate and a force parallel to the substrate is applied at a predetermined shear rate to obtain the maximum test force, and this value is defined as the solder shear strength. At this time, the shear height is ¼ or less of the component height, and the shear rate is 5 mm / min.

  And the value which showed in percentage the ratio of the solder shear strength which fell after the thermal shock test with respect to the solder shear strength of the soldering joint part before a thermal shock test is made into the fall rate (%) of solder shear strength. In the present specification, the solder shear strength of the solder joint means the solder shear strength of the solder joint with the flux residue attached.

  Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

1. Creating flux

<Preparation of synthetic resin>
Synthetic resins A to G were prepared by the following components and procedures.

Synthetic resin A
A solution in which 10% by weight of methacrylic acid, 51% by weight of 2-ethylhexyl methacrylate, and 39% by weight of lauryl acrylate were mixed was prepared.
Thereafter, 200 g of diethylhexyl glycol was charged into a 500 ml four-necked flask equipped with a stirrer, a flow tube and a nitrogen introduction tube, and heated to 110 ° C. Thereafter, dimethyl 2,2′-azobis (2-methylpropionate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) as an azo radical initiator was added to 300 g of the above solution from 0.2% by weight. 5% by weight was added to dissolve it.
This solution was added dropwise to the four-necked flask over 1.5 hours, and the components in the four-necked flask were stirred at 10 ° C. for 1 hour, and then the reaction was terminated to obtain a synthetic resin A. The weight average molecular weight of the synthetic resin A was 7,800 Mw, the acid value was 40 mgKOH / g, and the glass transition temperature was −47 ° C.

Synthetic resin B
Synthetic resin B is obtained under the same conditions as for preparation of synthetic resin A except that a solution in which 11% by weight of methacrylic acid, 25% by weight of 2-ethylhexyl methacrylate and 64% by weight of the compound represented by the following general formula (1) are mixed is used. It was. The weight average molecular weight of the synthetic resin B was 14,700 Mw, the acid value was 72 mgKOH / g, and the glass transition temperature was −71 ° C.

Synthetic resin C
A solution in which 46% by weight of hydrogenated acid-modified rosin (product name: KE-604, manufactured by Arakawa Chemical Co., Ltd.) and 54% by weight of dimer diol (product name: PRIPOL 2033, manufactured by Croda Japan Co., Ltd.) is prepared. did.
224 g of the above solution was placed in a 500 ml four-necked flask equipped with a stirring blade, a Dean-Stark apparatus and a nitrogen introduction tube, and stirred at 150 ° C. for 1 hour in a nitrogen atmosphere to dissolve the hydrogenated acid-modified rosin. .
Next, 5.7 g (0.03 mol) of p-toluenesulfonic acid monohydrate was added to the four-necked flask, and the temperature was raised to 180 ° C. to perform a dehydration reaction. This was allowed to react for 3 hours until dehydration ceased, then allowed to cool to room temperature, and further 200 g of ethyl acetate was added to make a homogeneous solution. This was neutralized with a saturated aqueous sodium hydrogen carbonate solution and concentrated after separation to obtain a synthetic resin C. Synthetic resin B had a weight average molecular weight of 5,340 Mw, an acid value of 10 mgKOH / g, and a glass transition temperature of −10 ° C. to −20 ° C.

Synthetic resin D
Use a solution in which 50% by weight of hydrogenated acid-modified rosin (product name: KE-604, manufactured by Arakawa Chemical Co., Ltd.) and 50% by weight of dimer diol (product name: PRIPOL 2033, manufactured by Croda Japan Co., Ltd.) are used. A synthetic resin C was obtained under the same conditions as in the production of the synthetic resin C except that. In addition, the weight average molecular weight of the synthetic resin D was 4,810 Mw, the acid value was 19 mgKOH / g, and the glass transition temperature was −10 ° C. to −20 ° C.

Synthetic resin E
Hydrogenated acid-modified rosin (product name: KE-604, manufactured by Arakawa Chemical Co., Ltd.) 52.5% by weight and dimer diol (product name: PRIPOL 2033, manufactured by Croda Japan Co., Ltd.) 47.5% by weight are mixed. A synthetic resin E was obtained under the same conditions as in the production of the synthetic resin C except that the prepared solution was used. In addition, the weight average molecular weight of the synthetic resin E was 3,850 Mw, the acid value was 26 mgKOH / g, and the glass transition temperature was −10 ° C. to −20 ° C.

Synthetic resin F
Epoxy resin (product name: EPICLON 1050, epoxy equivalent 450-500, softening point 64 ° C.-74 ° C., manufactured by DIC Corporation) was used.

Synthetic resin G
Phenoxy resin (product name: YP-70, weight average molecular weight 50,000-60,000 Mw, manufactured by Nippon Steel & Sumikin Co., Ltd.) was used.

<Preparation of flux>
Each component described in Table 1 was kneaded to obtain each flux of Examples 1 to 10 and Comparative Examples 1 and 2.

* 1 Hydrogenated acid-modified rosin manufactured by Arakawa Chemical Industries, Ltd. * 2 Antioxidant manufactured by BASF Japan Ltd.

<Adhesive strength>
For each flux, the adhesive strength of the flux residue was measured. The measuring method is as follows. The measured numerical values are shown in Table 2.

A glass epoxy board having a solder resist without a soldering pattern, a chip component having a size of 3.2 mm × 1.6 mm, and a thickness of 150 μm having an opening formed for mounting the chip component A metal mask was prepared.
Each flux was printed on the glass epoxy substrate using the metal mask, and the chip component was mounted. Thereafter, in a nitrogen atmosphere with an oxygen concentration of 1500 ± 500 ppm, each substrate is heated using a reflow furnace (product name: TNP-538EM, manufactured by Tamura Corporation) with a peak temperature set to 240 ° C., and flux residue The substrate and the chip component were bonded together.
Next, a thermal shock test apparatus (product name: ES-76LMS, set to -40 ° C (30 minutes) to 125 ° C (30 minutes) and -40 ° C (30 minutes) to 150 ° C (30 minutes). Using Hitachi Appliances Co., Ltd., each of the substrates was exposed to an environment in which the above thermal shock cycle was repeated 2000 times and then taken out to prepare each test substrate.
About each said test board | substrate, the adhesive force (adhesive force of a flux residue) of each board | substrate and the said chip component was measured using the autograph (Product name: EZ-L-500N, Shimadzu Corporation make). The measurement conditions were based on JIS regulations C60068-2-21. In measuring the adhesive strength, a shear jig having a flat end face and a width equal to or greater than the part size was used. The shear jig was abutted against the side surface of the chip component and a force parallel to the substrate was applied at a predetermined shear rate to obtain the maximum test force, and this value was defined as the adhesive force (N) of the flux residue. Further, this value was divided by the area of the chip component to calculate the adhesive force (N / mm ² ) of the flux residue. At this time, the shear height was ¼ or less of the component height, and the shear rate was 5 mm / min.

  Next, 11.0% by weight of each of the above fluxes and 89.0% by weight of Sn-3Ag-0.5Cu solder alloy powder (average particle size 20 to 36 μm) were mixed, and Examples 1 to 10 and Comparative Example Each solder paste according to 1 to 2 was prepared.

  Each solder paste and each flux were used for soldering, and the solder shear strength reduction rate and solder crack propagation at the soldered joint were measured and evaluated based on the results. These measurement methods and evaluation methods are as follows. The evaluation results are shown in Table 2.

<Solder shear strength reduction rate>
Each solder paste includes a chip component having a size of 3.2 mm × 1.6 mm, a solder resist having a pattern capable of mounting the chip component of the size, and an electrode (1.6 mm × 1.0 mm) for connecting the chip component. A glass epoxy substrate and a 150 μm thick metal mask having the same pattern were prepared.
Each solder paste was printed on the glass epoxy substrate using the metal mask. Next, using a dispenser (product name: ML-606GX, manufactured by Musashi Engineering Co., Ltd.), a predetermined amount of each corresponding flux was supplied onto the solder resist provided between the electrodes. Next, the chip component was mounted. Thereafter, in a nitrogen atmosphere with an oxygen concentration of 1500 ± 500 ppm, each of the substrates is heated and soldered using a reflow furnace (product name: TNP-538EM, manufactured by Tamura Corporation) with a peak temperature set to 240 ° C. A solder joint was formed. About each board | substrate which performed this soldering, the solder shear strength of the solder joint part on each board | substrate was measured using the autograph (Product name: EZ-L-500N, Shimadzu Corporation make).
Next, a thermal shock test apparatus (product name: ES-76LMS, set to -40 ° C (30 minutes) to 125 ° C (30 minutes) and -40 ° C (30 minutes) to 150 ° C (30 minutes). This was taken out after each substrate was exposed to an environment where the above-mentioned thermal shock cycle was repeated 2000 times using Hitachi Appliances. And the solder shear strength of the solder joint part on each board | substrate after this thermal shock test was measured using the autograph (Product name: EZ-L-500N, Shimadzu Corporation make).
The measurement conditions of the solder shear strength were all in accordance with JIS C60068-2-21. In the measurement of the solder shear strength, a shear jig having a flat end face and a width equal to or greater than the part size was used. The shear jig was abutted against the side surface of the chip component and a force parallel to the substrate was applied at a predetermined shear rate to obtain the maximum test force, and this value was defined as the solder shear strength of the solder joint. At this time, the shear height was ¼ or less of the component height, and the shear rate was 5 mm / min.
Then, the solder shear strength before the thermal shock test and the solder shear strength after the thermal shock test are compared, and a value indicating the percentage of the decreased shear strength as a percentage is obtained as a shear strength decrease rate (%) as follows. evaluated.
◎: Share strength decrease rate is 30% or less ○: Share strength decrease rate is over 30%, 50% or less ×: Share strength decrease rate is more than 50%

<Solder crack growth>
Each solder paste includes a chip component having a size of 3.2 mm × 1.6 mm, a solder resist having a pattern capable of mounting the chip component of the size, and an electrode (1.6 mm × 1.0 mm) for connecting the chip component. A glass epoxy substrate and a 150 μm thick metal mask having the same pattern were prepared.
Each solder paste was printed on the glass epoxy substrate using the metal mask. Next, using a dispenser (product name: ML-606GX, manufactured by Musashi Engineering Co., Ltd.), a predetermined amount of each corresponding flux was supplied onto the solder resist provided between the electrodes. Next, the chip component was mounted. Thereafter, in a nitrogen atmosphere with an oxygen concentration of 1500 ± 500 ppm, each of the substrates is heated and soldered using a reflow furnace (product name: TNP-538EM, manufactured by Tamura Corporation) with a peak temperature set to 240 ° C. A solder joint was formed.
Next, a thermal shock test apparatus (product name: ES-76LMS, set to -40 ° C (30 minutes) to 125 ° C (30 minutes) and -40 ° C (30 minutes) to 150 ° C (30 minutes). Using Hitachi Appliances Co., Ltd., each of the substrates was exposed to an environment in which the above thermal shock cycle was repeated 2000 times and then taken out to prepare each test substrate.
And the target part of each said test board | substrate was cut out, and this was sealed using the epoxy resin (Product name: Epomount (main agent and hardening | curing agent), refined tech Co., Ltd. product). Further, using a wet polishing machine (product name: TegraPol-25, manufactured by Marumoto Struers Co., Ltd.), the chip parts mounted on the test substrates are in a state where the center cross section can be seen, and the structure of the solder joints The length of the crack which progressed inside was evaluated as follows using a measuring microscope (product name: STM6, manufactured by Olympus Corporation).
○: Crack length is 0.5 mm or less ×: Crack length is more than 0.5 mm

As described above, as shown in the examples, the solder joint structure manufactured using the method for manufacturing a solder joint structure according to the present invention has a cycle of −40 ° C./30 minutes to 125 ° C./30 minutes, and −40 Adhesive strength after applying a thermal shock test with 2000 cycles of ℃ / 30 minutes to 150 ° C / 30 minutes as high as 3.5 N / mm ² or more, and firmly bonding electronic components and circuit boards Can do. Moreover, the solder joint part of this solder joint structure can suppress the crack growth by the said thermal shock test, and the fall of a shear strength is also suppressed resulting from this.
In particular, in the flux according to Example 1, both the −40 ° C. to 125 ° C. and −40 ° C. to 150 ° C. thermal shock tests show that the adhesive force of the flux residue increases as the thermal cycle is applied, and it is intense for a long time. Even when placed under a thermal shock cycle, sufficient adhesion can be exhibited.
Further, for example, as can be seen from FIGS. 5 and 8, the solder joint structure according to Example 1 has deep cracks even after the thermal shock test at −40 ° C. to 125 ° C. and −40 ° C. to 150 ° C. Therefore, high bonding reliability can be exhibited.
Furthermore, it is possible to provide a solder joint structure that exhibits the above effects regardless of the size of the pattern or electronic component provided on the circuit board.
As described above, the circuit board having the solder joint structure manufactured by using the method for manufacturing a solder joint structure according to the present invention is very suitable in an environment where a severe thermal shock cycle and vibration are applied for a long time. Can be used.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Insulation layer 3 Electrode part 4 Solder paste 5 Flux 6 Electronic component 7 External electrode 8 Solder joint part 9 Flux residue 10 End part 100 Solder joint structure 11 Board | substrate 12 Insulation layer 13 Electrode part 14 Solder paste 15 Flux 16 Electronic component 17 External electrode 18 Solder joint 19 Flux residue 20 End 200 Solder joint structure

Claims (6)

A method for manufacturing a solder joint structure including a solder joint for soldering a circuit board and an electronic component, and a flux residue,
A paste supplying step of supplying a solder paste containing a flux on the electrode portion provided on the circuit board;
A mounting step of mounting the electronic component on the circuit board;
A reflow process of reflowing the circuit board on which the electronic component is mounted to form a solder joint and a flux residue,
Before the mounting step, according to the pattern provided on the circuit board and the component and amount of the flux contained in the solder paste supplied onto the electrode part, Flux is supplied to a predetermined region other than the electrode part in the opposite region,
In the reflow step, the flux that oozes from the solder paste and the flux residue formed by at least one of the fluxes are at least between the circuit board or the insulating layer provided on the circuit board and the electronic component and the solder joint. Formed to adhere to these via
The adhesive force of the flux residue after 2000 cycles of the thermal shock test with -40 ° C / 30 minutes to 150 ° C / 30 minutes as one cycle is 3.5 N / mm ² or more,
At least one of the flux and the flux contained in the solder paste contains a synthetic resin, a thixotropic agent, an activator, and a solvent.   The method of manufacturing a solder joint structure according to claim 1, wherein the flux contained in the solder paste and the flux may have the same composition or different compositions.   The synthetic resins are acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, maleic acid ester, maleic anhydride ester, acrylonitrile, methacrylate. Acrylic resin obtained by polymerizing at least one monomer of nitrile, acrylamide, methacrylamide, and vinyl chloride vinyl acetate, and a derivative compound obtained by dehydration condensation of a rosin resin having a carboxyl group and a dimer acid derivative flexible alcohol compound. And at least one selected from the group consisting of epoxy resin, phenol resin, and rosin resin.   4. The solder according to claim 1, wherein in the paste supplying step, the flux is supplied to the predetermined region simultaneously with the supply of the solder paste onto the electrode portion. A method for manufacturing a bonded structure. A solder joint structure manufactured by the method for manufacturing a solder joint structure according to any one of claims 1 to 3 ,
The solder shear strength reduction rate is 50% or less before and after giving 2000 cycles of a thermal shock test of -40 ° C./30 minutes to 150 ° C./30 minutes to the solder joint structure. A feature of solder joint structure. A soldering method for soldering a circuit board and an electronic component,
Supplying a solder paste containing flux on the electrode portion provided on the circuit board;
Mounting the electronic component on the circuit board;
Reflow processing the circuit board on which the electronic component is mounted to form a solder joint, and soldering the circuit board and the electronic component.
Before mounting the electronic component on the circuit board, depending on the pattern provided on the circuit board and the component and amount of flux contained in the solder paste supplied on the electrode part, Supply the flux to a predetermined region other than the electrode part in the region facing the electronic component at the time of soldering,
In the reflow process, the flux oozing from the solder paste and the flux residue formed by at least one of the fluxes are at least between the circuit board or the insulating layer provided on the circuit board, the electronic component, and the solder joint. Formed to adhere to these via
The adhesive force of the flux residue after 2000 cycles of the thermal shock test with -40 ° C / 30 minutes to 150 ° C / 30 minutes as one cycle is 3.5 N / mm ² or more,
At least one of the flux and the flux contained in the solder paste includes a synthetic resin, a thixotropic agent, an activator, and a solvent.