JP2554915B2 - Cream solder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an improvement in cream solder.

<Problems to be Solved> Recently, in the printed circuit field, miniaturization of mounted chip parts and high circuit density have been dramatically promoted.

The chip components are mounted on the printed circuit board by the reflow method. That is, printing of cream solder on the printed circuit board according to its mounting pattern, temporary fixing of chip parts using the adhesiveness of cream solder, soldering by melting cream solder in a heating furnace, and cleaning removal of residual flux, etc. It is carried out through various processes. Therefore, with the miniaturization of chip parts and the increase in circuit density, there is a strong demand for improvement in the printing characteristics of cream solder.

The important printing characteristics of the cream solder are sagging property, bleeding property and the like, and it is known to add hydrogenated castor oil and amides in order to improve these properties.

However, the addition of hydrogenated castor oil inevitably causes a significant decrease in the cleanability of cream solder, making it difficult to clean the residual flux after soldering. Becomes extremely narrow and the insulation distance of the gap becomes extremely short, and this decrease in cleaning performance is a fatal defect.

On the other hand, it is difficult to expect the effects of amides unless added in a considerably large amount, and addition of a large amount has the disadvantage of damaging other properties such as tackiness.

Against this background, the present inventor has surprisingly found that the addition of an emulsifiable polyethylene wax is effective as a result of intensive studies to improve both the printing characteristics and the cleaning characteristics of cream solder.

<Means for Solving the Problems> The cream solder according to the present invention is based on such findings. In a solder in which a mixture of flux and powdered solder is creamed by a solvent, an emulsion type polyethylene wax is used. The composition is characterized by containing 1 to 12% by weight with respect to the flux content.

The emulsion-type polyethylene wax contributes to the improvement of the sagging property and the printing property of the blurring property, and the improvement of the cleaning property and the wiping-off property. The reason why the amount added is 1 to 12% is that when the amount is 2% or less, there is substantially no effect on the improvement of the above characteristics, and when the amount is 12% or more, the amount of polyethylene wax with respect to the amount of rosin becomes too large, which is the original function of rosin (cleaning). This is because the action, the antioxidant action ...) will be impaired.

The main composition of the cream solder is rosin, solvent,
An activator, an emulsifying polyethylene wax, and a powder solder, and a viscosity modifier, a corrosion inhibitor, etc. can be added. For its production, usually, a method in which a rosin, an activator and an emulsifying polyethylene wax are dissolved in a solvent to obtain a flux, and a powdered solder is kneaded can be used. For kneading, a homomixer, a dissolver, a roll Etc. can be used.

Emulsion type polyethylene wax has a molecular weight of 500-100
0, preferably 650 to 700, which is an oxidized type of low-medium-pressure polyethylene low-polymerization product, is different from non-emulsification type ordinary low-medium-pressure polyethylene low-polymerization product (shrinkage is 17%), and has a shrinkage ratio of 0. It is almost amorphous and has an acid value.

Polymerized rosin, natural rosin, hydrogenated rosin, maleated rosin, phenol-modified rosin, disproportionated rosin and the like can be used as the rosin.

As the activator, a hydrogen halide salt of a nitrogen-containing base such as diethylamine HCl can be used.

In addition to carbitol (diethylene glycol monoethyl ether), hexylene glycol, butyl cellosolve, propanediol, propylene glycol and the like can be used as the solvent.

The powdered solder can be appropriately selected from various conditions such as soldering temperature and bonding strength, and its particle size is 400 to 100 mesh.

The composition ratio of the cream solder is flux 5 to 15
%, Powder solder 95-85%, composition ratio of flux: rosin: 40-70%, solvent: 20-50%, emulsion type polyethylene wax: 1-12%, activator: 1%, other additions Agent: 0
~ 10%.

<Explanation of Examples> Hereinafter, the present invention will be described with reference to Examples in comparison with Comparative Examples.

Example 1 A solution obtained by adding 38 parts of carbitol to 55 parts of WW rosin was added to an emulsion type polyethylene wax (molecular weight: 650 to 700, density:
0.94 to 0.95, Softening point: Approx. 100 ° C, Penetration (25 ° C, 100g / se
c): 13 ± 5 polyethylene wax manufactured by Yasuhara Yushi Co., Ltd., neowax E) 6 parts, and diethylamine HCl 1 part were added to obtain a flux.

10 parts of this flux and 90 parts of powdered solder (Sn63-pd powdered solder, using 250 mesh) were kneaded to obtain a cream solder.

Example 2 A cream solder was obtained in the same manner as in Example 1 except that the flux having the composition shown in Table 1 was used.

Table 1 WW rosin 55 parts Galbitol 38 parts Emulsion type polyethylene wax 3 parts Hydrogenated castor oil 3 parts Diethylamine HCl 1 part Example 3 The same as Example 1 except that the flux having the composition shown in Table 2 was used. Got cream solder.

Table 2 WW Rosin 55 parts Galbitol 34 parts Emulsion type polyethylene wax 3 parts Stearic acid amide 7 parts Diethylamine HCl 1 part Comparative Example 1 Cream was prepared in the same manner as in Example 1 except that the flux having the composition shown in Table 3 was used. Got solder.

Table 3 WW rosin 55 parts Galbitol 38 parts Hydrogenated castor oil 6 parts Diethylamine HCl 1 part Comparative Example 2 A cream solder was obtained in the same manner as in Example 1 except that the flux having the composition shown in Table 4 was used.

Table 4 WW Rosin 55 parts Galbitol 29 parts Stearic acid amide 15 parts Diethylamine HCl 1 part For these example products and comparative product products, i sagging after screen printing ii Niiji iii Cream solder wipeability (wiping with squeegee rubber) The IV detergency (ultrasonic cleaning using CFC) and the V separability (40 ° C., left for 12 hours) were measured.

<Effects of the Invention> As is clear from these test results, Example product 1 is excellent in printability, cleanability, and separability,
It is clear that the emulsified polyethylene improves the washability better than hydrogenated castor oil (Comparative Example 1) and the printability better than stearamide (Comparative Example 2). Further, it is also effective when a part of the stearic acid amide is replaced with the emulsifying polyethylene wax (Example 3) or a part of the hydrogenated castor oil is replaced with the emulsifying polyethylene wax (Example 2). .

It should be noted that, in contrast to the above examples, non-emulsifying polyethylene wax (polyethylene wax manufactured by Yasuhara Yushi Co., Ltd., product name Neowax L) was used instead of the emulsifying polyethylene wax.
Was used, the cleaning property was remarkably inferior.

As described above, the cream solder according to the present invention is excellent in both printability and washability, and therefore, it is possible to mount a microminiature chip component on a high-density printed circuit with high accuracy, and further, after soldering. The short circuit caused by the remaining flux can be completely eliminated. Furthermore, it is difficult to separate (separation of powder solder and flux), and it has excellent long-term storability.

Claims (1)

(57) [Claims] 1. A solder in which a mixture of a flux and a powdered solder is made into a cream with a solvent, and an emulsion type polyethylene wax is contained in an amount of 1 to 12% by weight based on the flux.
Cream solder characterized by containing.