JP2520130B2 - Cream solder - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to cream solder.

2. Description of the Related Art Cream solder is made of resin (for example, natural rosin, disproportionated rosin, rosin-based resin such as hydrogenated rosin and polymerized rosin), solvent, activator and various additives (for example, viscosity modifier, antioxidant and deodorant). A cream-like solder in which powdered solder is dispersed in a flux containing a foaming agent, etc., and is mainly used by coating or printing on metal base materials to be joined.

The characteristics generally required for cream solder are that viscosity does not change during storage, solderability does not deteriorate, there is little offensive odor or toxicity, and cleaning after soldering is easy and workability is good. is there. Furthermore, with the recent high performance and miniaturization of products such as electronic devices, miniaturization, high-density mounting, and high integration of components to be joined using cream solder have been promoted. Performances such as high insulation, securing of joint strength and joint accuracy, and improvement of productivity and reliability are required, but in reality, conventional products cannot sufficiently meet these requirements.

One of the causes for this can be sought for the flux solvent. That is, ethylene glycol ethers (e.g., triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, ethylene glycol monohexyl ether, ethylene Glycol monophenyl ether etc.), dialkyl glycol ethers (eg diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether etc.), polyhydric alcohols (eg propylene glycol, butanediol, pentanediol, hexanediol, triethylene glycol) , Green Phosphorus, etc.) and the like are commonly used, the cream solder containing a combination of these solvents tend to cause viscosity changes in general during storage, is over time performance tends to be lowered.

In order to overcome the drawbacks of ethylene glycol ethers, that is, the toxicity is high, the volatility is relatively high, and the flexibility of the working process is limited due to the loss of tackiness in a short time. The plasticizer may be used in combination, but it decomposes over time to generate a strong acid, which not only lowers the reliability but also reduces the solubility and dispersibility of the activator and the rosin-based resin to locally Another problem of precipitation arises (local precipitation of the activator causes corrosion and local precipitation of the rosin-based resin leads to a marked decrease in printability).

Polyethylene alcohols such as triethylene glycol and glycerin have no problem in terms of volatility, but they have poor compatibility with rosin-based resins and have hygroscopicity, which causes solder to scatter during heating and increase solder balls. It has the drawback of causing

Furthermore, polyvalent carboxylic acids such as adipic acid and sebacic acid or higher saturated fatty acids such as stearic acid are used to promote the flux action, but it is not effective unless a relatively large amount is used. It causes deterioration of elastic properties and detergency.

Furthermore, there is a case to use unbranched aliphatic carboxylic acids, in this case, C ₁ -C ones strong irritating odor of _3, is corrosive and easy to absorb moisture, C ₄ ~ C ₉ has an unpleasant odor too strong, and C ₁₀ or more has a solid state, so that the viscosity characteristics required for cream solder cannot be obtained, and there is a problem that the cleanability is deteriorated.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention is a cream solder that does not have the above-mentioned drawbacks of the conventional cream solder, and in particular, there is no change in viscosity over time, solder balls and residues are small, and solderability is good. It was made to provide a cream solder that has characteristics such as high reliability, good peeling and drying time, long workability, low odor and toxicity, and good cleanability after soldering. It is a thing.

Means for Solving the Problems That is, the present invention has the general formula (I): (In the formula, R ₁ has 1 to 20 carbon atoms which may have a side chain.
It indicates an alkyl group, R ₂ represents an also alkyl group having 6 to 20 carbon atoms having a side chain. However, the total number of carbon atoms of the carboxylic acid containing R ₁ and R ₂ is 10 or more. The present invention relates to a cream solder containing either or both of a carboxylic acid represented by the formula (1) and its derivative.

The method for producing the carboxylic acid represented by the general formula (I) is not particularly limited, but it can be obtained, for example, by hydrogenation of an oxo reaction product using an olefin such as ethylene, propylene, butene or isobutene or a polymer thereof as a raw material. It can be obtained in high purity by oxidation of alcohol, oxidation of aldehyde aldol condensation product obtained by the oxo reaction, oxidation of Guerbet reaction product of lower alcohol, or the like.

The branching rate of the carboxylic acid represented by the general formula (I) depends on the type of reaction raw material and reaction conditions and is not particularly limited, but is usually about 45 to 100% wt, and particularly 85 to 100% wt. .

Examples of such carboxylic acid include 2-methylnonanoic acid, 2-methyldecanoic acid, 2-methylundecanoic acid, and 2
-Methyldodecanoic acid, 2-methyltridecanoic acid, 2-methyltetradecanoic acid, 2-pentylnonanoic acid, 2-hexyldecanoic acid, 2-heptylnonanoic acid, 2-heptylundecanoic acid, 2-octyldodecanoic acid, 2-decyltetradecane Examples thereof include acid, 2-decyldodecanoic acid, 2-undecyldodecanoic acid, 2-decylpentadecanoic acid and 2-undecyltetradecanoic acid, with 2-heptylnonanoic acid being particularly preferred.

The carboxylic acid represented by the general formula (I) has the following characteristics, for example.

1) Almost odorless, high-purity higher carboxylic acid that is liquid at room temperature and has no toxicity.

2) It has low volatility and high boiling point, which enhances the dry resistance of cream solder.

3) Since the compatibility with the base resin is excellent, the change with time of the viscosity of the cream solder is reduced.

4) Since it has appropriate solubility in the activator, it suppresses the precipitation of the activator which causes corrosion.

5) Low hygroscopicity enables long-term storage of cream solder and extension of standing time after application or printing, and prevents increase in viscosity and formation of solder balls.

6) The viscosity and boiling point can be freely adjusted by appropriately selecting the production conditions.

7) It has excellent oxidation resistance and good cleaning properties after soldering.

8) very acid value is high (e.g., acid number of the carboxylic acids of C ₁₀ -C ₃₆ is 326 to 104), it indicates effective flux effect, the resin being mandatory in the conventional solder paste one It is possible to substitute some or all of them, and it is possible to increase the degree of freedom in formulation.

Examples of the derivative of the carboxylic acid represented by the general formula (I) include esters with various alcohols having 1 to 36 carbon atoms (such as butyl isostearate (butyl 2-hexyldecanoate)) and the like.

This type of ester is much more stable against hydrolysis than butyl carbitol acetate, diisobutyl adipate, etc., which have been compounded in conventional cream solders, and stably dissolves the base resin.

If desired, two or more kinds of the above carboxylic acids and their derivatives may be used in combination.

When either or both of the carboxylic acid represented by the general formula (I) and its derivative are contained, the total amount of both is not particularly limited, but is usually about 2 relative to the total weight of the cream solder flux. -80% by weight, preferably about 40-70% by weight.

The flux of the cream solder according to the present invention usually contains a base resin (for example, polymerized rosin, natural rosin,
Hydrogenated rosin, maleated rosin, disproportionated rosin, etc.)
And an activator (for example, a hydrogen halide salt of a nitrogen-containing base, an organic acid salt, an organic acid, an amino acid, etc.) are appropriately mixed.

If desired, conventional additives may be appropriately added to the flux. Known solvents as such additives (for example, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, triethylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, ethylene glycol, polyethylene Glycol, propylene glycol, dipropylene glycol, butanediol, hexylene glycol, etc.), plasticizer (eg dioctyl phthalate), viscosity modifier (eg waxes such as hydrogenated castor oil, ultrafine silica powder, etc.), oxidation Examples include an inhibitor (for example, BHT), an antifoaming agent (for example, a silicon-based antifoaming agent), and the like.

The cream solder according to the present invention can be obtained by kneading and mixing the conventional powdered solder with the flux obtained by the above-mentioned formulation by a conventional method. The amount of the flux to be blended is not particularly limited, but is usually about 8 to 16% by weight, preferably about 10 to 14% by weight based on the total weight of the cream solder.
Is.

 The invention will be further described by the following examples.

Examples 1 to 12 Cream solders 1 to 12 were prepared by sufficiently kneading 87 parts by weight of powdered solder (Pb / Sn = 37/63, 250 mesh) and 13 parts by weight of flux according to the formulation of Table-1.

 The characteristics of these cream solders are shown in Table-2.

The meanings of the evaluation symbols A to C of the characteristics of the cream solder in Table 2 are as follows: 1) Viscosity change A; Almost no change, B; Visible change in usable amount, C; Unusable Viscosity changes to some extent 2) Solubility of activator A: Good, B: Cold precipitation, C: Insoluble 3) Residue after printing (extent of residue after 8 hours of printing) A: No change, B; Slightly Increase, C; Remarkably increase 4) Residue after application (degree of residue after reflow after 100 hours of application) A: Very low, B; Low, C; High 5) Solderability (soldering to oxidized copper plate A) Excellent, B; Usable, C; Bad 6) Odor (degree of odor generated during reflow) A: Odorless, B; Odorous, C; Unpleasant odor 7) Adhesive (24 hours after application) Adhesive strength of chip parts up to) A: 24 hours possible, B: 12 hours possible, C: 12 hours not possible 8) Resin stability (in flux after 100 days have passed since preparation) Resin state) A: Transparent, B; Turbid, C: Crystallized 9) Copper plate corrosion (JIS Z 3197) A; Pass, C; Fail 10) Detergency (boiling cleaning using Freon AES) A: Excellent , B: Good, C: Poor 11) Insulation (JIS Z 3197) A: Pass, C: Fail Comparative Examples 1 to 7 Cream solders 1 ′ to 7 ′ were prepared according to Examples 1 to 12.

 The characteristics of these cream solders are shown in Table-2.

EFFECTS OF THE INVENTION The carboxylic acid represented by the general formula (I) used in the present invention does not deteriorate the viscoelasticity and the cleanability of the cream solder at all even when it is added in a relatively large amount as a flux solvent, and it does not generate solder balls. In addition, it maintains good flux characteristics, has no unpleasant odor, and is economically relatively inexpensive.

Furthermore, since the carboxylic acid has excellent oxidation resistance,
Not only the cleanability after soldering is good, but also the effective flux action is exhibited, so that a part or all of the resin which is indispensable in the conventional cream solder can be replaced.

Therefore, the cream solder according to the present invention provides high productivity and reliability, and is particularly suitable for mass production of high-density mounting boards.

Claims (5)

(57) [Claims] 1. General formula (I): (In the formula, R ₁ has 1 to 20 carbon atoms which may have a side chain.
It indicates an alkyl group, R ₂ represents an also alkyl group having 6 to 20 carbon atoms having a side chain. However, the total number of carbon atoms of the carboxylic acid containing R ₁ and R ₂ is 10 or more. ) A cream solder containing either or both of a carboxylic acid represented by the following formula and a derivative thereof. 2. The cream solder according to claim 1, wherein the carboxylic acid represented by the formula (I) is a carboxylic acid produced by oxidation of an alcohol obtained by hydrogenation of an oxo reaction product using an olefin as a raw material. 3. The cream solder according to claim 2, wherein the olefin is ethylene, propylene, butene, isobutene or a polymer thereof. 4. A carboxylic acid represented by the formula (I) is 2-methylnonanoic acid, 2-methyldecanoic acid, 2-methylundecanoic acid, 2-methyldodecanoic acid, 2-methyltridecanoic acid, 2-methyltetradecanoic acid, 2-pentylnonanoic acid, 2-hexyldecanoic acid, 2-heptylnonanoic acid, 2
-Heptylundecanoic acid, 2-octyldodecanoic acid, 2
-Decyltetradecanoic acid, 2-decyldodecanoic acid, 2-
The cream solder according to claim 1, which is one or more carboxylic acids selected from the group consisting of undecyldodecanoic acid, 2-decylpentadecanoic acid and 2-undecyltetradecanoic acid. 5. The cream solder according to claim 1, wherein the derivative of the carboxylic acid represented by the formula (I) is an ester.