JP2696412B2 - Cream solder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a cream solder in which a solder powder and a flux are mixed for use in soldering a microcircuit or the like. By using an amine hydrohalide,
There is no occurrence of solder balls of the resulting cream solder,
The present invention relates to a cream solder having excellent anti-skinning properties and good solderability.

(Prior Art) Conventionally, soldering has been frequently used when electronic elements are mounted on a printed circuit board. In order to make the soldering more reliable in the soldering, a method of cleaning the surface of the metal to be joined with a liquid flux or a high-viscosity flux and then soldering, or a so-called cream solder in which the solder fine particles and the flux are mixed is used. The method used is widely used.

The above-mentioned liquid flux and flux for cream solder are used in order to maintain high product quality and reliability.
High insulation, (2) non-corrosive, (3) long-term stability, (4)
It is required that the material of other parts does not change. From the soldering work side, (1) no harmful gas is generated, (2) good solderability (has the action of removing oxides on the metal surface and wrapping the metal surface, (Which lowers the surface tension), (3)
When not washed, there is no stickiness. (4) When washing, it is required to be easily washed.

Generally, the cream solder is prepared by mixing powdery solder particles with a liquid or paste-like flux to form a cream having a suitable viscosity. The flux generally uses rosin as a base material and contains a solvent, an activator, a thixotropic agent and the like. The composition of the flux is very important because the characteristics of the cream solder obtained vary slightly depending on the type and the mixing ratio of these compounding agents. The solder can be arranged by printing and applying such cream solder to the conductor surface of the printed circuit board, and the adhesiveness of the cream solder allows the electronic components to be adhered and held on the conductor surface. It is very useful as compared to

Although cream solder has the above-mentioned advantages compared to solution flux, etc., it reacts during storage due to the mixing of the flux containing the solder fine particles and the activator, causing a change in viscosity and skin tension (upper layer of cream solder). Part curing),
Problems such as decreased activity have been pointed out. These problems are particularly remarkable when an amine salt of hydrogen halide or the like is used as the activator. Therefore, it is desired to reduce the amount of the activator added or not to add the activator. However, when the amount of the activator is decreased, there is a problem that the soldering property is deteriorated, and in particular, the solder balls are increased. Solder balls, which are generally described, are printed immediately after the manufacture of cream solder, and solder balls when reflowed immediately after printing and solder balls that have been generated for a long time after cream solder production, There is a solder ball or the like which is generated due to being left for a long time (usually one day or more) after printing. The present invention is mainly directed to the generation of solder balls due to aging.

In order to eliminate or reduce the amount of the hydrogen halide-based activator, it is generally necessary to add another activator. For example, JP-A-57-52588 discloses a method using salicylic acid and succinic acid.
However, salicylic acid has a strong odor, and succinic acid is difficult to use because it tends to cause skinning during storage of cream solder. Japanese Patent Application Laid-Open No. 58-13491 has released the method of using benzyl acid as an activator. However, the activator is also difficult to use because it tends to cause skinning and hardening during storage of cream solder. JP-A-60-203387 discloses a method using a halogen monocarboxylic acid or an amine salt thereof. However, because the activator is likely to decompose during storage to generate hydrogen halide, or during storage, skinning, hardening, etc., are extremely likely to occur, and solder balls are also likely to occur. Even, it was difficult to use even an amine with a hydrohalide. Therefore it is hard to cause skinning during storage,
And an activator that does not easily generate solder balls due to long-term storage or leaving after printing, especially with the above characteristics,
There has been a strong demand for an amine hydrohalide activator having good solderability.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned drawbacks of the prior art, contains an amine hydrohalide salt, has good solderability and cleanability, and has little change over time during storage. It provides cream solder.

(Means for Solving the Problems) An object of the present invention is to provide the drawbacks of the above-described conventional techniques, particularly, the skinning of cream solder containing a hydrogen halide-based activator during storage of the cream solder, and the long standing after printing. It is an object of the present invention to provide an extremely good cream solder in which the generation of solder balls (hereinafter simply referred to as solder balls) at the time of occurrence is prevented and improved. More specifically, as an activator of a flux, hydrogen chloride of an amine having a specific structure is used. By adding acid and / or hydrobromide,
It is to provide the finest cream solder that has not been obtained before.

That is, the present invention is a cream solder obtained by mixing a powder solder and a liquid or paste-like flux,
A cream solder characterized in that the flux contains a trialkylamine hydrochloride and / or hydrobromide represented by the following general formula (I).

(However, R ₁ and R ₂ are a saturated alkyl group having 1 to 6 carbon atoms) Hereinafter, the present invention will be described in detail.

The flux in the present invention contains a hydrochloride and / or hydrobromide of an amine represented by the formula (I). The amine salt may be used alone, or two or more of the amine salts may be used in combination or other conventionally known activators such as a hydrogen halide activator, a carboxylic acid activator, and a halogenocarboxylic acid activator. It can also be used in combination with an agent.

In the present invention, R ₁ and R ₂ of the amine represented by the formula (I) are a saturated alkyl group having 1 to 6 carbon atoms. Incidentally, a saturated alkyl group and a chain hydrocarbon group having no unsaturated bond,
It represents an alicyclic hydrocarbon group, and may contain a hydroxyl group, an ether group, a halogen, or the like in each group, but among these, a linear lower hydrocarbon group is particularly preferable. . R ₁ and R ₂ may be the same or different.

Examples of the amine represented by the formula (I) in the present invention include cyclohexyldimethylamine, cyclohexyldiethylamine, cyclohexylmethylethylamine, cyclohexyldi-n-propylamine, cyclohexyldiisopropylamine, cyclohexyldi-n-butylamine, and cyclohexyl. Examples thereof include diisobutylamine, cyclohexyldipentylamine, cyclohexyldihexylamine, and dicyclohexylmethylamine. Of these, cyclohexyldimethylamine and cyclohexyldiethylamine are particularly preferred in terms of preventing the occurrence of solder balls and preventing skinning.

In the present invention, the acid component of the activator containing the amine represented by the formula (I) is hydrochloric acid and / or hydrobromic acid. Among them, hydrobromic acid is particularly preferred in terms of skin tonicity.

The content of the amine hydrochloride and / or hydrobromide in the flux in the present invention is not particularly limited, but is particularly preferably 1 to 5% by weight. If the amount is less than 1% by weight, the activity may be insufficient, and if the amount exceeds 5% by weight, the active agent may be increased, and the anti-skinning property may be slightly reduced.

The trialkylamine hydrochloride and / or hydrobromide activators of the present invention may be used alone as described above, but may also be used in combination with other activators. is there. These activators which can be used in combination include conventionally known hydrogen halide activators. However, since hydrogen halide-based activators have strong activity,
Although it has good solderability and is widely used,
It is said that due to its excessively strong activity, problems such as a change over time (change in viscosity, skin tension, etc.) of the cream solder, deterioration of corrosiveness due to slight residual after washing, and deterioration of electric insulation are caused. For this reason, users of cream solders are demanding ones with the lowest possible halogen content. Therefore, the activator used in combination with the activator of the present invention is particularly preferably an activator other than the hydrogen halide activator. Examples of these activators include malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, dicarboxylic acids such as dicarboxylic acid or monoamine salts thereof, monochloroacetic acid, dichloroacetic acid,
Examples thereof include monobromoacetic acid, dibromoacetic acid, α-chloropropionic acid, α-bromopropionic acid, β-chloropropionic acid, β-bromopropionic acid, 1,2-bromosuccinic acid, and amine salts thereof.

The solder powder in the present invention is not particularly limited, but the shape may be spherical or irregular, and the particle size of the solder powder may be any commonly used one, but in the case of spherical, the diameter is 20 to 60 μm. Are particularly preferred.
Furthermore, the composition of the solder alloy is not particularly limited,
Preferred are Sn-Pb-based alloys, Sn-Pb-Bi-based alloys, Sn-Pb-Ag-based alloys, and the like.

Although the composition of the flux in the present invention is not particularly limited, it can be produced by blending a rosin, a polymerized rosin, a disproportionated rosin, a solvent, an activator, a thixo agent and the like in addition to the activator of the present invention.

The solvent to be added to the flux in the present invention is not particularly limited, but alcohols such as α-terpineol, hexylene glycol, methyl carbitol, butyl carbitol, benzyl alcohol, isopalmityl alcohol, isostearyl alcohol, diisobutyl acylate, Esters such as diethyl phthalate and dibutyl phthalate, hydrocarbons such as dodecylbenzene, and phosphate esters such as triethyl phosphate and tripentyl phosphate can be preferably used.

The thixotropic agent to be added to the flux in the present invention is not particularly limited, but oleic acid amide, stearic acid amide, hydrogenated castor oil and the like are preferable.

The content of the flux in the cream solder in the present invention is not particularly limited, but is preferably in the range of 7 to 13% by weight.

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

(Example) Example 1 (1) Preparation of flux 50 parts of polymerized rosin, 15 parts of α-terpineol, 14 parts of hexylene glycol, 12 parts of dibutyl phthalate, 2.0 parts of HBr salt of cyclohexyldimethylamine, and 7 parts of hydrogenated castor oil Was charged in a container, melted by heating, and then cooled.

(2) Preparation of cream solder In a container, 90 parts of 250-500 mesh Sn / Pb (63 wt% / 37 wt%) solder powder and 10 parts of the flux prepared in (1) were taken and stirred to obtain a cream.

(3) Evaluation of cream solder The cream solder obtained in section (2) was soldered according to a conventional method (Galaeppo board, 235 ° C reflow), solder balls (cream on an Al ₂ O ₃ plate with a diameter of 4 mm, thickness) 0.3mm
And left at room temperature x 48 hours, reflow at 230 ° C,
Observed with a stereomicroscope), Freon detergency (Freon 113 /
(Ethanol = 96/4, immersion for 2 minutes at room temperature without stirring), corrosiveness and skininess of the cream were evaluated. The soldering property and the chlorofluorocarbon cleaning property were very good, and the solder ball generation preventing property and the corrosion preventing property were good. Furthermore, the skinning of the cream solder was very good without any skinning.

Example 2 HB of cyclohexyldimethylamine in Example 1
r A cream solder was prepared and evaluated in the same manner as in Example 1 except that the amount of the salt was changed as shown in Table 1, and the changed amount was corrected with dibutyl phthalate. Table 1 shows the evaluation results. In addition, each evaluation was determined based on the following criteria.

As is evident from Table 1, when the cyclohexyldimethylamine HBr salt is added, it is very good, and when the addition amount is 1 to 5% by weight, it is particularly good.

Example 3 In Example 1, cyclohexyldimethylamine HBr was used.
A cream was prepared and evaluated in the same manner as in Example 1 except that an activator as shown in Table 2 was added instead of the salt. Table 2 shows the evaluation results.

As is clear from Table 2 and Example 1, in the case of the activator of the present invention, it is well balanced and comprehensive. On the other hand, in the case of Comparative Examples 1 and 2, which are conventionally known activators, the anti-soldering property and anti-skinning property are poor and poor.

(Effects of the Invention) According to the present invention, it is possible to produce a cream solder having good solder ball generation preventing property and anti-skinning property, as well as good soldering properties and cleaning properties, as compared with conventionally known techniques.

Claims (3)

(57) [Claims] 1. A cream solder obtained by mixing a powder solder and a liquid or paste-like flux, wherein the flux contains a trialkylamine hydrochloride and / or bromide represented by the following general formula (I): A cream solder containing a hydrochloride. (However, R ₁ and R ₂ are saturated alkyl groups having 1 to 6 carbon atoms) 2. The cream solder according to claim ₁ , wherein R ₁ and R ₂ in the formula (I) are a methyl group or an ethyl group. 3. The method according to claim 1, wherein the content of the hydrochloride and / or hydrobromide of the amine in the flux is 1 to 5% by weight. The cream solder described.