JPH0647189B2 - Cream solder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cream solder that is frequently used in the electric and electronic fields, particularly for soldering a printed circuit board or the like.

(Prior Art) Cream solder is mainly used for connecting a board and an electronic component. The soldering is performed by first applying an appropriate amount of cream solder to a predetermined area on the board by printing or a dispenser, and then applying the cream solder onto the cream solder. The electronic parts are mounted on and heated by a reflow furnace, hot plate, hot air, laser beam, high temperature steam, etc. to melt the solder and perform soldering.

In addition, general properties required for cream solder are (1) moderate viscosity and good printability (2) good solderability (3) no toxicity or odor (4) The viscosity does not change for a long period of time, and the surface is not peeled.

In recent years, as electronic devices have become smaller and higher in density, the land patterns of board circuits have become smaller and the land spacing has become narrower. The cream solder used for these is also printable, washable, and reliable. Is required to improve.

By the way, cream solders are roughly classified into oil-soluble cream solders based on rosin and water-soluble cream solders based on a water-soluble composition such as glycerin, polyethylene glycol, polypropylene glycol, and diethylene glycol.

In the latter case, when the flux residue is removed after the soldering is completed, these cream solders can be washed with water, but in the former case, an organic solvent such as chlorocene or freon must be used.

However, in recent years, there is an increasing tendency to regulate the use of organic solvents from the viewpoint of environmental damage and occupational health, and there is a strong demand for a shift from washing with organic solvents to washing with water.

Washing with water has the following advantages when compared with washing with an organic solvent.

(1) Water is nonflammable as a solvent and is extremely easy to handle.

(2) Water has no environmental damage.

(3) Water is cheaper than any organic solvent.

(4) Water is said to be the best solvent, especially for ionic substances such as activators used in cream solder.

By the way, as the oil-soluble cream solders, those which almost satisfy the above-mentioned performance have been commercialized, but in the case of the water-soluble cream solders, they are still insufficient and printability and cleanability are problems.

One of the causes can be found in the flux base carrier.

That is, in oil-soluble cream solder, rosin is used as the base carrier of the flux, whereas in flux of water-soluble cream solder, there is no suitable material that serves as a base carrier that dissolves in water instead of rosin.

Polyethylene glycol and polypropylene glycol are commonly used in current water-soluble cream solder,
However, using these as a base carrier, cream solder, when moved on a screen mask with a squeegee,
Since it lacks in consistency and adhesiveness, it does not roll sufficiently and slides sideways, resulting in insufficient filling of the solder into the screen opening, which deteriorates printability to the substrate.

(Problem to be Solved by the Invention) An object of the present invention is to provide a cream solder capable of cleaning and removing flux components with water without using any organic solvent such as Freon after the completion of soldering.

(Means for Solving the Problems) The inventors of the present invention have conducted various studies to achieve such an object and found that tris- (2,3-epoxypropyl) -isocyanurate (hereinafter abbreviated as “TEPIC”). The present invention has been completed based on the knowledge that the reaction product of) and a compound containing a carboxyl group has such characteristics.

Here, the gist of the present invention is that one or two or more carboxyl group-containing compounds selected from the group consisting of monocarboxylic acids having 8 or less carbon atoms, polycarboxylic acids and hydroxylcarboxylic acids and tris- (2,3-Epoxypropyl) -isocyanurate, which is a cream solder prepared by mixing a solder powder with a flux containing a resinous substance which is a reaction product with (3) -isocyanurate.

(Function) According to the present invention, the resinous substance used for the flux component is, of course, water-soluble so that the flux component can be washed and removed with water after the soldering is completed. In particular, it must be an amphipathic substance that dissolves in the organic solvent used for cream solder, and it must not decompose when the solder is melted and heated.

Therefore, the resinous substance used in the present invention includes (a) a monocarboxylic acid having 8 or less carbon atoms, (b) a hydroxylcarboxylic acid having 8 or less carbon atoms and having a hydroxyl group, and (c) also carbon atoms. A polycarboxylic acid having a number of 8 or less and having two or more carboxyl groups in the molecule, one or more carboxyl group-containing compounds (hereinafter also simply referred to as “carboxylic acid”) selected from Those obtained by reacting with-(2,3-epoxypropyl) -isocyanurate are preferred.

That is, not only those having a hydroxyl group such as hydroxylcarboxylic acid (b), but also those not having a hydroxyl group such as mono- or polycarboxylic acids (a) and (c), the epoxy group of TEPIC The reaction product of generating an ester group and a hydroxyl group by the addition reaction of OH imparts water solubility to the product.

Further, the aralkyl group of these carboxyl group-containing compounds imparts solvent solubility.

However, when a carboxyl group-containing compound having a carbon number of more than 8 is used, the solubility in a solvent is good, but the water solubility is extremely lowered. Therefore, in the present invention, the carbon number is limited to 8 or less.

Specific examples of such monocarboxylic acid (a) include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, caproic acid, enanthic acid, caprylic acid and the like.

Specific examples of the hydroxylcarboxylic acid (b) include glycol, lactic acid, hydroxybutyric acid, hydroxyvaleric acid and the like.

Further, specific examples of the polycarboxylic acid (c) include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid and suberic acid.

Specific examples of the hydroxycarboxylic acid (b) and the polycarboxylic acid (c) include malic acid, citric acid, tartaric acid and hydroxymalonic acid.

However, the carboxylic acid used in the present invention is not particularly limited thereto, and the above-mentioned carboxylic acids (a), (b), as long as the objects and effects of the present invention are exhibited.
Any carboxyl group-containing compound (c) may be used.

Such a carboxylic acid is reacted with tris- (2,3-epoxypropyl) -isocyanurate represented by the following general formula to obtain a resinous substance.

The reaction product of this compound and the carboxylic acid (referred to as RCOOH for convenience) can be represented by the following general formula.

In the formula, _one of X ₁ and X ₂ is a carboxylic acid residue RCOO-), the other is an OH group, and one of Y ₁ and Y ₂ is a carboxylic acid residue (RCOO-). And
The other is an OH group, one of Z ₁ and Z ₂ is an RCOO group, and the other is an OH group, an isocyanurate derivative, and the reaction product is presumed to consist of a mixture thereof. When polycarboxylic acid is used, it is considered that some components are oligomerized.

As the production conditions for these resinous substances, TEPIC may be heated to 130 ° C. or higher and melted, and then the above-mentioned carboxylic acid may be added and reacted, or a suitable solvent and a reaction accelerator such as a tertiary amine may be added. You may go. The reaction time of these is usually about 1 to 10 hours, and the carboxylic acid may be added after mixing the respective components in advance, or may be added separately and stepwise.

The molar ratio of the reaction is 1 to 6 mol in total amount of carboxylic acids per 1 mol of TEPIC, more preferably 1 to 3 mol.
It is a mole. In short, it is preferable to make the residual epoxy amount as small as possible.

The resinous substance thus obtained is used as Fuchs, and the solder powder is blended into it, but the solder powder used in the present invention is not particularly limited, and the same kind as that usually used in cream solder is used. The particle size may be used. Preferably, the following types of alloys can be exemplified. That is, Sn-Pb, Sn-Pb-Ag, Sn-Ag,
Examples are Sn-Pb-Bi and Pb-In. The particle size of these solder alloys is preferably 200-400 mesh.

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

Example <Reaction example 1> TE was placed in a four-necked flask equipped with a stirrer, a thermometer, and a cooling tube.
PIC-S (Nissan Chemical Co., Ltd., high-purity product of tris- (2,3-epoxypropyl) -isocyanurate. Epoxy equivalent
100 g / EQ, ie, 1 gram equivalent of epoxy group per 100 g) is added, and 300 parts by weight is added, and the temperature is adjusted to 13 after melting at 140 ° C.
The temperature was adjusted to 0 ° C. and the mixture was stirred. While adding 180 parts by weight of acetic acid little by little, the reaction was carried out for 2 hours and then at 140 ° C. for 1 hour.

Then, the reaction system was slowly cooled to obtain a starch syrup-like product.

From the results of measuring the epoxy value of the product by the perchloric acid titration method, the amount of residual epoxy was below the detection limit of the titration method.
The acid value was 0.22 mol / kg.

<Reaction Example 2> In the same manner as in Reaction Example 1, with respect to 300 parts by weight of TEPIC-S,
Add 162 parts by weight of acetic acid little by little and react at 130 ° C for 2 hours, then add 27 parts by weight of lactic acid little by little and then add 140 ° C.
And reacted for 1 hour. Then, the reaction system was slowly cooled to obtain a starch syrup-like product.

The epoxy value of the product is below the detection limit and the acid value is 0.47.
It was mol / kg.

<Reaction Example 3> In the same manner as in Reaction Example 1, 150 parts by weight of acetic acid was added little by little, and the mixture was reacted at 130 ° C for 1.5 hours, and then adipic acid.
After adding 73 parts by weight, the mixture is reacted at 140 ° C for 1.5 hours. Then, the system was cooled slowly to obtain a starch syrup-like product.

The epoxy value of the product is below the detection limit and the acid value is 0.97.
It was mol / kg.

<Reaction Example 4> In the same manner as in Reaction Example 1, lactic acid (180 parts by weight) was added little by little, adipic acid (146 parts by weight) was added, and the mixture was reacted at 130 ° C for 15 hours and then at 140 ° C for 2 hours. Let Then, the reaction system was slowly cooled to obtain a starch syrup-like product.

The epoxy value of the product is below the detection limit and the acid value is 2.08.
It was mol / kg.

The conditions and results for the above reaction examples are shown in Table 1.

Examples and Comparative Examples Powder solder (Sn 63% -Pb, 200 mesh, spherical powder) 90wt
% And each of the fluxes in Table 2 were mixed to prepare a cream, and the obtained cream solder was tested for printability, solderability, cleanability, and viscosity change over time. The results are summarized in Table 3.

The conventional example shows an example of a conventional water-soluble cream solder.

Here, the printability evaluation test in the above characteristic test was performed in the following manner.

Printability test: Cream solder was printed on the substrate with a metal mask (0.2 t), and the printed state (bleeding, scraping, bridge, etc.) was visually observed, and three-level evaluation was performed.

Solderability test: The cream solder printed on the substrate was reflowed to examine the wetting property of the solder and the amount of solder balls generated, and the same three-stage evaluation was performed.

Detergency test: 60 after reflowing the cream solder printed on the board
It was immersed in warm water at ℃ for 5 minutes and then rinsed to check for the presence of flux residue. Also in this case, the evaluation was made in three stages.

Regarding the change in viscosity, the viscosity was measured immediately after the cream solder was manufactured and one month after the cream solder was manufactured, and this was also evaluated in three levels.

From the results in Table 3, it can be seen that the cream solder according to the present invention is superior to that of the comparative example in printability, solderability, cleanability, and change in viscosity. In particular, the detergency and printability are superior to those of any of the comparative examples, and the excellent effects of the present invention are clear. In particular, it can be seen that, compared with the conventional one, both the printability and the washability, which have been problems in the past, are improved to the extent that they are satisfied.

(Effects of the Invention) As described in detail above, the cream solder according to the present invention has good solderability and excellent printability, and the flux residue after soldering is easily washed with water only. Since it can be removed, it has an unprecedented excellent effect that it is safe from the viewpoint of occupational hygiene, without the fear of environmental damage unlike the organic solvent washing type cream solder.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hisao Ikeda 1 722, Tsuboi-cho, Funabashi-shi, Chiba Central Research Laboratory, Nissan Chemical Industries, Ltd. (72) Minoru Taguchi 405, Yatsuka-cho, Soka-shi, Saitama Senju Metal Works (72) Inventor Shozo Asano 405, Yatsuka-cho, Soka-shi, Saitama Senju Metal Industry Co., Ltd.

Claims (1)

[Claims] 1. Tris- (2,3-epoxypropyl) and one or more carboxyl group-containing compounds selected from the group consisting of monocarboxylic acids having 8 or less carbon atoms, polycarboxylic acids and hydroxylcarboxylic acids. ) -Cream solder obtained by mixing a flux containing a resinous substance which is a reaction product with isocyanurate and solder powder.