JP2520128B2 - 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 solders are that there is no change in viscosity during storage, solderability does not deteriorate, and there is no offensive odor or toxicity and workability is good. In particular, as products such as electronic devices have become higher in performance and smaller in size in recent years, miniaturization, high-density mounting and high integration of components to be joined using cream solder have been promoted, which is also high in cream solder. Performances such as insulation, bonding strength and bonding accuracy, and improvement of productivity and reliability are required, but in reality, conventional products cannot fully 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.) and polyhydric alcohols (eg propylene glycol, butanediol,
(Pentanediol, hexanediol, triethylene glycol, glycerin, etc.) are commonly used, but cream solders containing these solvents generally tend to undergo viscosity changes during storage and tend to deteriorate in performance over time. .

In order to overcome the drawbacks of ethylene glycol ethers, that is, the relatively high volatility and the loss of tackiness in a short time, which limits the flexibility of the work process, mainly when an ester plasticizer is used in combination. However, there is another problem that 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 and locally deposits these. Occurs (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

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. The purpose of the present invention is to provide a cream solder having characteristics such as high reliability, absence of peeling and drying, long working time, good workability, and little bad smell or toxicity.

Means for Solving the Problems That is, the present invention provides a cream solder having the above-mentioned requirements by using a specific primary alcohol having a side chain and a relatively large molecular weight as a flux solvent. It was made based on the finding that it can be obtained, and its gist is 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 alcohol including R ₁ and R ₂ is 10 or more. ) A cream solder containing either or both of an alcohol represented by the formula (1) and a derivative thereof.

The alcohol represented by the general formula (I) is, for example, hydrogenation of an oxo reaction product starting from an olefin (eg, ethylene, propylene, butene, isobutene, etc.),
It can be obtained in high purity by hydrogenation of an aldol condensation product of an aldehyde obtained by the oxo reaction, a Guerbet reaction of a lower alcohol, or the like.

The branching ratio of the alcohol 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 about 85 to 100% wt.
Is.

Examples of such alcohol include 2-methylnonanol, 2-methyldecanol, 2-methylundecanol, 2-methyldodecanol, 2-methyltridecanol, 2-methyltetradecanol, and 2-pentylnonanol. 2-hexyldecanol, 2-heptylnonanol, 2-heptylundecanol, 2-octyldodecanol, 2-decyltetradecanol, 2-decyldodecanol, 2-undecyldodecanol, 2-decyl Pentadecanol, 2-undecyltetradecanol and the like are exemplified, but 2-heptylnonanol is particularly preferable.

The alcohol represented by the general formula (I) has, for example, the following properties: 1) It is a synthetic higher alcohol which is almost odorless and 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 coating 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.

Examples of the derivative of the alcohol represented by the general formula (I) include alkylene oxide, for example, an adduct with ethylene oxide or propylene oxide, and esters such as phthalate, acetate and adipate. 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 of the above alcohols and their derivatives may be used in combination.

When either or both of the alcohol represented by the general formula (I) and the derivative thereof are contained, the total compounding amount of the both is not particularly limited, but is usually about 2 to the total weight of the cream solder flux. It is 80% by weight, preferably about 40-70% by weight. The flux of the cream solder according to the present invention comprises a base resin (for example, polymerized rosin, natural rosin, hydrogenated rosin, maleated rosin, disproportionated rosin, etc.) and an activator (for example, hydrogen halide of nitrogen-containing base) in the above components. Acid salt, organic acid salt, organic acid, 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.

 Hereinafter, the present invention will be described with reference to examples.

Examples 1 to 23 Cream solders 1 to 23 were prepared by thoroughly kneading 87 parts by weight of powdered solder (Pb / Sn = 40/60, 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 for the characteristics of the cream solder in Table 2 are as follows.

1) Viscosity change A; No change at all, B; Viscosity change at usable level, C;
Viscosity changes to the extent that it cannot be used 2) Solubility of activator A; Good, B; Precipitation during cold, C; Insoluble 3) Residue after printing (residual extent 8 hours after printing) A; No change, B ; Slightly increased, C; Significantly increased 4) Residue after application (degree of residue when immediately reflowed after application) A: Very low, B; Low, C; High 5) Residue after aging (after application) , Degree of residue when reflowed after 100 hours) A: No change, B: Slightly increased, C: Remarkably increased 6) Solderability (solderability to oxidized copper plate) A: Excellent, B; Use Possible, C; Bad 7) Odor (degree of odor generated during reflow) A: Odorless, B; Odorous, C unpleasant odor 8) Adhesive (degree of adhesion of chip product within 24 hours after application) A; 24 hours possible, B; 12 hours possible, C; 12 hours not possible 9) Resin stability (resin state in flux after 100 days of preparation) A; transparent, B; cloudy, C; Crystallization 10) Copper plate corrosion A: No corrosion, B: Discoloration, C: Corrosion Comparative Examples 1 to 5 Cream solders 1 ′ to 5 ′ were prepared according to Examples 1 to 23.

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

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

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 (6)

(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 alcohol including R ₁ and R ₂ is 10 or more. ) A cream solder containing one or both of an alcohol represented by the formula (1) and its derivatives. 2. The cream solder according to claim 1, wherein the alcohol represented by the formula (I) is 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. The alcohol represented by the formula (I) is 2-methylnonanol, 2-methyldecanol, 2-methylundecanol, 2-methyldodecanol, 2-methyltridecanol, 2-methyltetradecanol. Decanol, 2-pentylnonanol, 2-hexyldecanol, 2-heptylnonanol, 2-heptylundecanol, 2-octyldodecanol, 2-decyltetradecanol, 2-
Decyldodecanol, 2-undecyldodecanol, 2
-The cream solder according to claim 1, which is one or more alcohols selected from the group consisting of decyl pentadecanol and 2-undecyl tetradecanol. 5. The cream solder according to claim 1, wherein the alcohol derivative represented by the formula (I) is an adduct of alkylene oxide. 6. The cream solder according to claim 1, wherein the alcohol derivative represented by the formula (I) is an ester of a carboxylic acid.