JP2001232496A - Flux for soldering and solder paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide flux for soldering in which failures caused by the reduction of the plasticity of a flux residue is suppressed and to provide solder paste using the same. SOLUTION: This flux for soldering contains a resin and a solvent, rosin is used as the resin, polyhydric alcohol or the derivative thereof having the melting point of >=245 deg.C is used as the solvent, and also, the solvent content is 40 to 90 pts.wt. to 100 pts.wt. of rosin. Since, in this flux for soldering, the sufficient solvent remains in the flux residue produced after soldering, cracking and peeling do not occur in the flux residue, to the effect that failures are not generated in the soldered jointed part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a soldering flux used in soldering and a solder paste using the same.

[0002]

2. Description of the Related Art As one method of joining objects,
There is soldering. This bonding by soldering is used for bonding between metals, and is particularly used for bonding various elements to a substrate in an electronic circuit board or the like.

[0003] Soldering is a method of joining by melting and inflowing a solder alloy made of a metal or an alloy having a lower melting point than that of the base material without melting the base material, without melting the base material. .

In this soldering, a soldering flux is used. By using the soldering flux, bonding by soldering becomes strong.
More specifically, the oxide film present on the surface of the joining base material is removed by the soldering flux to prevent the solder alloy and the joining base material from being oxidized. In addition, wetting is improved by lowering the surface tension of the molten solder alloy,
The molten solder alloy flows into the gaps of the joining base material, and the joining becomes stronger.

[0005] The soldering flux has a resin such as rosin and a solvent that dissolves the resin to facilitate handling. Further, other additive components such as an activator are appropriately compounded in the soldering flux.

In actual soldering, not only high-temperature soldering, but also lead-free soldering, a conventional Pb-Sn eutectic alloy is used depending on the type of alloy used at the soldering temperature. In many cases, the temperature was much higher than the soldering temperature of the solder alloy.

Further, when soldering is performed using a conventional soldering flux at a high soldering temperature of 245 ° C. or higher, there is a problem that plasticity is not generated in the residual flux after soldering. Was.

[0008] Here, the flux residue is a degraded substance of the soldering flux remaining after the soldering, and in the soldering using the soldering flux,
It is an inevitable substance.

When plasticity is not generated in the flux residue, cracking or peeling occurs in the flux residue, and when a soldered member is used, the portion where the cracking or peeling occurs causes moisture contained in the air to be present. Is dewed to cause migration failure, or the flux residue is ionized, thereby corroding a solder alloy or a joining base material.

However, if the solvent is excessively added to maintain the plasticity of the flux residue, the degree of drying of the flux residue becomes insufficient, and dust and the like contained in the atmosphere such as the atmosphere are reduced by the flux residue. It adheres to the surface, and the attached dust and dust causes a short circuit.

As described above, when soldering is performed at a high temperature using a soldering flux, problems such as poor migration are likely to occur due to a decrease in the plasticity of the flux residue.

[0012]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and a soldering flux and a solder paste using the same, in which the occurrence of problems due to a decrease in plasticity of the flux residue is suppressed. The task is to provide

[0013]

Means for Solving the Problems To solve the above problems, the present inventors have paid attention to the fact that a decrease in the plasticity of the flux residue is caused by the volatilization of the solvent contained in the soldering flux. As a result of repeated studies on the solvents contained in the above, it has been found that a flux for soldering that can solve the above-mentioned problems can be provided by using a solvent having a high boiling point and by limiting the amount thereof.

That is, the soldering flux of the present invention is a soldering flux having a resin and a solvent, wherein the resin is rosin and the solvent has a boiling point of 245.
It is a polyhydric alcohol or a derivative thereof at a temperature of at least ℃, and is contained in an amount of 40 to 90 parts by weight based on 100 parts by weight of rosin.

Since the soldering flux of the present invention uses a solvent having a high boiling point, even when soldering at a high temperature, a sufficient solvent remains in the flux residue to ensure plasticity. For this reason, problems such as poor migration due to a decrease in plasticity of the flux residue do not occur.

Further, the solder paste of the present invention is a solder paste comprising a soldering flux having a resin and a solvent, and a solder alloy powder, wherein the resin is rosin, and the solvent has a boiling point of 245 ° C. or higher. Or a derivative thereof, and is contained in an amount of 40 to 90 parts by weight based on 100 parts by weight of rosin.

Since the solder paste of the present invention uses a high-boiling solvent for the soldering flux, even when soldering at a high temperature, sufficient solvent remains in the flux residue to ensure plasticity. ing. For this reason, problems such as poor migration due to a decrease in plasticity of the flux residue do not occur.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Soldering Flux) The soldering flux of the present invention has a resin and a solvent.

As the resin, rosin is used. As the rosin, a rosin such as a natural rosin, a hydrogenated rosin, and a polymerized rosin can be used as long as it has a carboxyl group in the molecule.

The solvent comprises a polyhydric alcohol having a boiling point of 245 ° C. or higher or a derivative thereof. By using a polyhydric alcohol having a boiling point of 245 ° C. or more or a derivative thereof as a solvent, the solvent remains in the flux residue even when soldering at a high temperature of 245 ° C. or more, and the plasticity of the flux residue is maintained. . That is, the solvent does not volatilize even at a high soldering temperature and remains in the soldering flux.

The solvent is 40 parts by weight based on 100 parts by weight of rosin.
It is contained at 90 parts by weight. By setting the blending amount of the solvent to 40 to 90 parts by weight with respect to the rosin, the solvent remains in the flux residue after soldering at a high temperature, and the plasticity of the flux residue is maintained.

If the polyhydric alcohol or a derivative thereof is less than 40 parts by weight based on 100 parts by weight of rosin, the plasticity of the flux residue is lost, and
If the amount exceeds the weight part, the residue of the flux will be tested for dryness (JIS
Z3192), the adhesion of chalk powder is observed. Further, when the amount of the solvent exceeds a predetermined amount, when the soldering flux is used for the solder paste, a problem occurs in the printability of the solder paste.

The solvent is preferably glycol or a derivative thereof having compatibility with rosin. Since the solvent has compatibility with rosin, in the flux residue generated by soldering, separation of the rosin and the solvent does not occur, and cracking of the flux residue does not occur.
Here, the fact that the solvent has compatibility with rosin indicates that the solvent has high solubility in rosin.

The solvent is butyl carbitol acetate,
It is preferable that the material be at least one selected from dibutyl carbitol, hexyl carbitol, and ethylene glycol monophenyl ether acetate. That is, these compounds have a boiling point of 245 ° C. or higher,
Has high compatibility with rosin. The boiling points of these compounds are shown in Table 1. Further, a mixture obtained by mixing these compounds may be used as the solvent. At this time, the mixture
It is mixed to have compatibility with rosin and a boiling point of 245 ° C. or higher.

[0025]

[Table 1]

The soldering flux of the present invention preferably has an additive. Examples of the additive include an activator. The type of the activator is not particularly limited. However, the activator volatilizes at the soldering temperature and hardly remains, and an organic acid or a salt thereof that does not adversely affect the electrical insulation even if a little remains. Are preferred. Examples of the activator include aromatic carboxylic acids and aliphatic carboxylic acids, more specifically, benzoic acid, o-toluic acid, salicylic acid, phthalic acid, diphenylacetic acid, and the like, adipic acid, succinic acid, and glutaric acid. ,
Sebacic acid and the like can be mentioned.

Further, as additives other than the activator, oils and fats such as castor oil and the like, and thixotropic agents can be mentioned. The mixing ratio of these additives is not particularly limited, and the mixing ratio generally used can be directly applied depending on the usage form of the soldering flux.

In the soldering flux of the present invention, since the solvent remains in the flux residue after soldering,
The plasticity of the flux residue is guaranteed. For this reason, cracks and peeling do not occur in the flux residue, and problems such as migration do not occur.

The flux for soldering of the present invention can be used as a general flux or a flux for cored solder, and is more preferably used for a solder paste.

The soldering flux of the present invention can be handled in the same manner as a conventional soldering flux. That is, when used for soldering, the soldering flux of the present invention does not require special handling, and can be used in the same composition as a conventional soldering flux.

(Solder Paste) The solder paste of the present invention comprises a soldering flux, a solder alloy powder,
Consists of

As the solder alloy powder, a powder of a solder alloy used in a conventional solder paste can be used. That is, as the solder alloy, a conventional lead-based solder alloy, a lead-free solder made of a Sn-Ag eutectic alloy, or the like can be used. The particle size and shape of the solder alloy powder are not particularly limited, and may be in a powder state that can be used for ordinary solder paste.

The flux for soldering has a resin and a solvent.

As the resin, rosin is used. As the rosin, a rosin such as a natural rosin, a hydrogenated rosin, and a polymerized rosin can be used as long as it has a carboxyl group in the molecule.

The solvent comprises a polyhydric alcohol having a boiling point of 245 ° C. or higher or a derivative thereof. By using a polyhydric alcohol having a boiling point of 245 ° C. or more or a derivative thereof as a solvent, the solvent remains in the flux residue even when soldering at a high temperature of 245 ° C. or more, and the plasticity of the flux residue is maintained. . That is, the solvent does not volatilize even at a high soldering temperature and remains in the soldering flux.

The solvent is 40 parts by weight based on 100 parts by weight of rosin.
It is contained at 90 parts by weight. By setting the amount of the solvent to be 40 to 90 parts by weight with respect to the rosin, the solvent remains in the flux residue after soldering at a high temperature, and the plasticity of the flux residue is maintained.

When the amount of the polyhydric alcohol or its derivative is less than 40 parts by weight based on 100 parts by weight of the rosin, the plasticity of the flux residue is lost, and when the amount exceeds 90 parts by weight, a drying test (JISZ31)
92), the chalk powder adheres. Further, when the amount of the solvent exceeds a predetermined amount,
When the soldering flux is used for the solder paste, a problem occurs in the printability of the solder paste.

The solvent is preferably a glycol compound compatible with rosin. When the solvent has compatibility with rosin, a sufficient amount of rosin can be blended into the soldering flux. Here, the fact that the solvent has compatibility with rosin indicates that the solubility in rosin is high.

The solvent is butyl carbitol acetate,
It is preferable that the material be at least one selected from dibutyl carbitol, hexyl carbitol, and ethylene glycol monophenyl ether acetate. That is, these compounds have a boiling point of 245 ° C. or higher,
Has high compatibility with rosin. The boiling points of these compounds are shown in Table 1. Further, a mixture obtained by mixing these compounds may be used as the solvent. At this time, the mixture has compatibility with rosin and 245
It is mixed so as to have a boiling point of not less than ° C.

It is preferable that the solder paste of the present invention has an additive. Examples of the additive include an activator. The type of the activator is not particularly limited. However, the activator volatilizes at the soldering temperature and hardly remains, and an organic acid or a salt thereof that does not adversely affect the electrical insulation even if a little remains. Are preferred. Activators include, for example, aromatic carboxylic acids,
Aliphatic carboxylic acids, more specifically, benzoic acid, o-toluic acid, salicylic acid, phthalic acid, diphenylacetic acid and the like, adipic acid, succinic acid, glutaric acid, sebacic acid and the like can be mentioned.

As additives other than the activator, oils and fats such as castor oil and the like, and thixotropic agents can be mentioned. The mixing ratio of these additives is not particularly limited, and the mixing ratio generally used can be directly applied depending on the usage form of the soldering flux.

Further, in the solder paste of the present invention,
The ratio of solder alloy powder to soldering flux is
The ratio can be the same as that used in the conventional solder paste.

Since the solder paste of the present invention uses a high-boiling solvent for the soldering flux, even if soldering is performed at a high temperature, cracking and peeling of the flux residue generated after soldering is suppressed. I have. For this reason, the solder paste of the present invention is particularly useful for soldering at high temperatures.

[0044]

The present invention will be described below with reference to examples.

As an example, a soldering flux of the present invention and a solder paste using the same were prepared.

(Soldering Flux) As examples, soldering fluxes of Samples 1 to 6 and Comparative Examples 7 to 13 were prepared.

More specifically, the raw materials were weighed and adjusted at the ratios shown in Table 2 and dissolved by heating to 150 ° C. in a sufficiently mixed state. Was prepared.

[0048]

[Table 2]

Here, the solvent type is the solvent shown in Table 1,
Polymerized rosin was used for rosin, glutaric acid was used for the activator, castor oil was used for fats and oils, and hardened castor oil was used for additives.
Commercial reagents were used for each reagent.

(Solder Paste) Using the soldering fluxes of Samples 1 to 13 and a Sn-Ag eutectic alloy,
Solder paste samples 1 to 13 were prepared.

More specifically, the solder paste is prepared by mixing the above-mentioned soldering fluxes of Samples 1 to 13 and Sn-Ag eutectic alloy powder in an appropriate amount so that the viscosity becomes 200,000 to 250,000 cps. It was made by pasting. Here, the Sn-Ag eutectic alloy powder has a particle size of 2
The melting temperature was 221 ° C.

(Evaluation) As an evaluation of the solder paste of the example, a test pattern was printed using the prepared solder paste, and the printability, the thermal shock resistance, and the dryness were tested. Was.

First, the solder paste samples 1 to 6 of the examples
Was printed on a test pattern of an epoxy substrate (FR-4), and heat treatment was performed at a maximum heating temperature of 250 ° C. using a reflow furnace.

Here, the printability of the solder paste was evaluated by visually checking the solder paste printed on the epoxy substrate. Table 3 shows the results of the visual evaluation.
It was shown to. Here, ○ and × shown in the printability results
The symbol “○” indicates a state in which no bleeding or bleeding was observed, and the symbol “X” indicates a state in which no bleeding or bleeding was observed.

[0055]

[Table 3]

As shown in Table 3, Samples 9 to 12 as Comparative Examples
The printed pattern was blurred and blurred. It is considered that the dripping and bleeding of the printing occurred due to a large amount of the solvent contained in the soldering flux.

Further, in Samples 9 to 12 of the comparative examples in which a defect occurred during printing, when a heating was performed in a reflow furnace, a bridge defect occurred.

After the heat treatment of the test pattern in the reflow furnace was completed, a drying test of the flux residue was performed. The test for the dryness of the flux residue was conducted according to JISZ3197.
The test was performed using the test method specified in The test results are shown in Table 3. In Table 3, ○ and × shown in the results of the dryness test indicate that ○ indicates no adhesion of chalk powder, and × indicates the state where adhesion of chalk powder was observed.

From Table 3, it can be seen that Samples 1 to 5 according to the examples of the present invention were used.
In No. 6, no adhesion of chalk powder was observed, and no stickiness was observed on the surface of the flux residue. On the other hand, it was confirmed that chalk powder adhered to each of the samples 11 to 13 as the comparative examples.

Here, the reason why the chalk powder was adhered to each of the comparative samples 11 to 13 in the dryness test was that samples 11 and 12 had the same amount of solvent as the weight of rosin. Since the amount of the solvent is excessive, it is considered that chalk powder is attached. In addition, it is considered that chalk powder adhered to sample 13 because the amount of the solvent was small, but the compatibility with rosin was low, and separation was caused between the rosin and the solvent in the flux residue. Can be

Then, using a thermal shock tester, -30
This heat cycle was repeated with one cycle of maintaining the temperature at 30 ° C. for 30 minutes and maintaining the temperature at 80 ° C. for 30 minutes, and the number of cycles when the flux residue cracked was measured. The residual cracks were confirmed using a 30 × stereo microscope using a QFP.
(0.65 mm) by observing the portion between lands. Table 3 shows the measurement results.

From Table 3, it can be seen that Samples 1 to 3 of the present invention were used.
Sample No. 6 did not show any cracks in the flux residue even after 1000 cycles, indicating that it was excellent in thermal shock resistance. In Samples 7 to 10, the residual crack was 300
It was confirmed at the beginning of the test, which was about a cycle.

As described above, Samples 1 to 5 according to the embodiment of the present invention were obtained.
No. 6 is excellent in printability, test results of drying test after heating and thermal shock test. That is, the solder pastes of Samples 1 to 6 are free from cracking or peeling of the flux residue even when soldering is performed at a high soldering temperature of 250 ° C. As a result, the soldering flux and solder paste of Samples 1 to 6 specified in the present invention can be used for soldering at a high temperature.

[0064]

According to the soldering flux of the present invention, since sufficient solvent can be left in the flux residue generated after soldering, the flux residue does not crack or peel off, and the soldered joint has a problem. No longer occurs. Therefore, the solder paste of the present invention
Particularly useful for soldering at high temperatures.

Continuing on the front page (72) Inventor Daisuke Yoshidome 3-65 Midorigaoka, Toyota-shi, Aichi Prefecture Inside Daitoyo Kogyo Co., Ltd. (72) Inventor Naofumi Takao 41 Co., Ltd. Inside the Toyota Central Research Institute (72) Inventor Eiichi Sudo 41-41, Chuchu-Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Institute, Inc. (72) Inventor Makoto Akizuki No. 1 Inside Solder Coat Co., Ltd. (72) Inventor Masahiro Sugiura 75 Term Nagata, Narumi-cho, Midori-ku, Nagoya-shi, Aichi F-term within 1 Solder Coat Co., Ltd. 5E319 BB05 CD21 GG03

Claims (6)

[Claims] 1. A soldering flux comprising a resin and a solvent, wherein the resin is a rosin, the solvent is a polyhydric alcohol having a boiling point of 245 ° C. or higher or a derivative thereof, and the rosin 100 A flux for soldering, comprising 40 to 90 parts by weight with respect to parts by weight. 2. The soldering flux according to claim 1, wherein the solvent is glycol or a derivative thereof compatible with the rosin. 3. The solvent comprises butyl carbitol acetate, dibutyl carbitol, hexyl carbitol,
3. The soldering flux according to claim 2, comprising at least one member selected from ethylene glycol monophenyl ether acetate. 4. A solder paste comprising a soldering flux having a resin and a solvent, and a solder alloy powder, wherein the resin is rosin, and the solvent is a polyhydric alcohol having a boiling point of 245 ° C. or more or A solder paste which is a derivative thereof and is contained in an amount of 40 to 90 parts by weight based on 100 parts by weight of the rosin. 5. The solder paste according to claim 4, wherein the solvent is glycol having a compatibility with the rosin or a derivative thereof. 6. The solvent comprises butyl carbitol acetate, dibutyl carbitol, hexyl carbitol,
6. The solder paste according to claim 5, comprising at least one selected from ethylene glycol monophenyl ether acetate.