JPH10249577A - Soldering cream - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soldering cream that enables high density mounting. SOLUTION: A thixotropy agent is made from hydrofined castor oil and bisamide composed of 12-hydroxystearic acid and diamine, with these mixed under a desirable combination ratio, quantity and conditions, constituting a flux in which no coarse filler is caused and in which a strong thixotropic character is contained, creating a superior coating property with a fine solder power dispersed in the flux, and thereby producing a soldering cream free of shear drop and oxidation. One example of a desirable combination ratio is the flux in which 3 to 10 parts of thixotropy agent are contained in 100 parts of flux. In addition, the thixotropy agent is prepared in such weight % as 1 hydroxystearic acid against 0.3-1.0 bisamide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder cream capable of coping with high-density mounting.

[0002]

The solder cream is prepared by dispersing a solder powder in a flux prepared by dissolving a rosin, an activator, a thixotropic agent and other additives in a solvent. Or printed or applied by dispenser discharge. Therefore, it is strongly required that the solder cream has good printing characteristics and ejection characteristics, and that the applied material does not sag or bleed, and the filler effect due to fine precipitation of the thixotropic agent and other additives in the solder cream. Has been used effectively.

However, as the solder cream application pattern becomes finer and denser as the substrate is mounted, the thixotropic agent and additive deposited fillers which have been used effectively become coarse obstacles relatively to the fine pattern. However, effective application results cannot be obtained. In order to respond to the same reason, the fineness of the solder powder further reduced the thixotropic properties of the solder cream, and caused a significant change in printing characteristics and ejection characteristics with changes in viscosity and consistency,
In addition to the resulting failures, sagging and bleeding became more likely. In view of such current problems, urgent improvement of solder cream is required in order to appropriately cope with the progress of high-density packaging.

[0004] Castor oil and its derivatives are known as powerful thixotropic agents. The same applies to bisamides of various higher fatty acids and diamines. Therefore, these have often been used alone or in combination as fluxes. Both are relatively poor in compatibility with the rosin and the solvent constituting the flux and are difficult to uniformly blend into the system. Therefore, they are dissolved in the system at a temperature close to the melting point at the time of blending. And when these are adopted as thixotropic agents,
Originally, due to the property of forming strong hydrogen bonds, in the process of cooling from a high-temperature molten state to room temperature, thixotropic agents gathered together to form colonies and precipitated out as fillers. In particular, the higher the melting point, the more the tendency is remarkable, and a considerable part of the compounded thixo agent is consumed for filler precipitation other than formation of a network containing a solvent and a solute. Thus, the obtained flux shows a liquid flow. Further, when the thixotropic agent is increased to compensate for such a problem, the viscosity and consistency of the flux tend to increase unnecessarily. However, with the aid of rough solder powder, even if the lead pitch of the IC was 0.5 mm or more, it was possible to respond tentatively.

However, in recent high-density mounting, a lead pitch of about 0.5 mm is insufficient, and soldering corresponding to a finer pitch is required.

An object of the present invention is to provide a solder cream which can be mounted at a higher density than the current situation.

[0007]

In order to achieve the above object, in the present invention, hydrogenated castor oil and a bisamide of 12-hydroxystearic acid and a diamine are used as thixotropic agents,
Combining these in a preferred ratio combination, amount and conditions, without generating coarse fillers, and constituting a flux having strong thixotropy, dispersing fine solder powder into it to achieve excellent coating performance, This is a solder cream with no dripping or bleeding.

As an example of a combination of the above preferable ratios, there is a case where a flux containing 3 to 10 parts of a thixotropic agent in 100 parts of a flux is used. Bisamide may be blended in a weight ratio of 0.3 to 1.0 with respect to 1 hydrogenated castor oil.

Among castor oil derivatives and various amides, unsaturated fatty acids are not preferred because they have a low melting point and the low-temperature dripping properties of solder cream are poor. Hydrogenated castor oil and amides, among which higher fatty acids having a hydroxyl group in the side chain, especially bisamides with diamine of 12-hydroxystearic acid are good, but the thixotropy of the flux alone is not sufficient, and the filler There are many precipitations. In particular, the latter is remarkable. However,
It has been found that when both are used in a preferable ratio, the precipitation is greatly reduced, and the morphology of the precipitation is fine, and the thixotropy is also greatly improved. It is presumed that the combined use inhibited the crystallization of the thixotropic agent. The solder cream using the flux thus obtained has a lead pitch of 0.3 m.
m or less.

Bisamides include methylene, ethylene, hexamethylene, and xylylene bisamides (hereinafter, referred to as "bisamides").
(Collectively referred to as bisamides) are useful in industrial practicality. The hydrogenated castor oil preferably has a high softening point, and is preferably at least 70 ° C. or higher, and more preferably completely hydrogenated castor oil. An appropriate amount of the thixotropic agent is 3 to 10 parts by weight with respect to 100 parts by weight of the flux. If it is lower than this, the thixotropy is insufficient, and if it is higher than that, the viscosity is excessive, undesired consistency is developed, and coarse fillers are easily generated.

The ratio of hydrogenated castor oil to bisamide is preferably 1: 0.3 to 1: 1 by weight. Bisamide is 0.
If it is less than 3, the coating performance will be poor, such as poor solder roll printing rollability due to insufficient consistency.
If it is more than 1.0, the consistency will be too high and the printing will be poor,
The coating performance is degraded, for example, due to increased precipitation of coarse filler. When producing a flux in the present invention,
It is necessary to finely disperse the thixotropic agent in a solution in which a composition other than rosin and other components other than the thixotropic agent is uniformly mixed and dissolved in advance, uniformly disperse and mix the mixture, and then heat and stir. The thixotropic agent is made into fine powder, preferably 50 μm or less in advance, and is uniformly dispersed and mixed. After the thixotropic agent is dispersed and mixed, the mixture is desirably cooled to room temperature with stirring.

In order to correspond to a fine pattern of 0.3 mm pitch, the solder powder should be 50 μm or less, preferably 40 μm or less.
Submicron is better. 85-92% by weight of this solder powder
In addition, the solder cream kneaded with 15 to 8% by weight of the flux disclosed in the present invention can cope extremely well with print application and discharge application of fine patterns.

[0013]

【Example】

(Example 1) 55.5 parts of polymerized rosin, 19 parts of diethylene glycol monohexyl ether, 19 parts of diethylene glycol monobutyl ether, and 0.5 part of diethylamine hydrobromide are uniformly dissolved at 120 ° C. After cooling to room temperature, 2.5 parts of N, N'-ethylenebis-12-hydroxystearic acid amide and hydrogenated castor oil 3.5
The fine powder mixture was uniformly mixed so as not to cause mamako, and then heated with stirring, and then cooled to room temperature. The flux obtained in this way is a smooth gel-like substance without a thixotropic agent or other coarse precipitates and exhibits high thixotropy. A solder cream obtained by kneading 10 parts of this flux and 90 parts of a solder powder of 35 μm or less has high thixotropy and exhibits extremely excellent printability in fine pattern printing of 0.3 mm pitch. There was no sagging or bleeding on the coated material.

(Examples 2 to 5) N, N'-methylenebis-12-hydroxystearic acid amide (Example 2), N, N'-butylenebis12
-Hydroxystearic acid amide (Example 3), N,
N'-hexamethylenebis-12-hydroxystearic acid amide (Example 4), N, N'-xylylenebis12
Other components substituted by -hydroxystearic acid amide (Example 5) were constituted in the same manner as in Example 1, and an experiment was conducted under the same conditions. As a result, the obtained solder cream showed almost the same properties as in Example 1.

Example 6 A homogeneous solution of 58.5 parts of polymerized rosin, 19 parts of diethylene glycol monohexyl ether, 19 parts of diethylene glycol monobutyl ether and 0.5 part of diethylamine hydrobromide was added to a homogeneous solution of N, N'-ethylenebis. 12-hydroxystearic acid amide 1.5
Parts and 1.5 parts of hydrogenated castor oil were dispersed at room temperature in such a manner that no mamako was formed, the temperature was increased while stirring, and then cooled to room temperature with stirring. To 13 parts of the flux thus obtained, 87 parts of solder powder having a size of 35 μm or less were kneaded to obtain a solder cream. The solder cream was stably discharged from a 0.2 mm diameter needle hole, and no dripping was observed in the applied material.

Example 7 A homogeneous mixed solution of 48.5 parts of polymerized rosin, 20.5 parts of diethylene glycol monohexyl ether, 20.5 parts of diethylene glycol monobutyl ether, and 0.5 part of diethylamine hydrobromide was prepared.
A fine powder mixture of 3 parts of N, N'-ethylenebis-12-hydroxystearic acid amide and 7 parts of hydrogenated castor oil is uniformly dispersed and mixed at room temperature without mamaco, and the mixture is heated while stirring, and then stirred. While cooling to room temperature. 10 parts of the flux thus obtained and 90 parts of solder powder having a diameter of 35 μm or less were kneaded to obtain a solder cream. This solder cream showed good results for printing a fine pattern of 0.3 mm pitch.

Comparative Example 1 N, N'-ethylenebis12
The same procedure as in Example 1 was repeated except for using 3.5 parts of hydroxystearic acid amide and 2.5 parts of hydrogenated castor oil to obtain a solder cream. This solder cream had excessive consistency and poor printing, and printing at a pitch of 0.3 mm failed to obtain a sufficient effect.

Comparative Example 2 N, N'-ethylenebis12
A solder cream was obtained in the same composition as in Example 6, except that 1 part of hydroxystearic acid amide, 1 part of hydrogenated castor oil and 59.5 parts of polymerized rosin were used. This solder cream had unstable ejection and dripping of the applied matter was large.

Comparative Example 3 N, N'-ethylenebis12
-A solder cream was obtained with the same composition as in Example 7 except that the mixed fine powder having a ratio of hydroxystearic acid amide to hydrogenated castor oil of 3: 7 was 12 parts, and the polymerized rosin was 46.5 parts. . In this solder cream, coarse thixotropic agents were noticeably precipitated in the flux, and the solder cream itself lacked smoothness. When printing was performed at 0.3 mm pitch, only unstable results were shown.

The above results are summarized in Table 1.

[Table 1]

[0021]

As in the scope of the present invention, use is made of a flux produced under appropriate ratios, amounts and conditions of disamide of hydrogenated castor oil, 12-hydroxystearic acid and diamine. As a result, good coating characteristics could be obtained even when using fine solder powder. Therefore, it is possible to cope with a fine pattern of 0.3 mm pitch, which is required recently, and it is possible to increase the density of the substrate mounting.

Claims (3)

[Claims] 1. A solder cream comprising a flux comprising at least a rosin, an activator, a solvent and a thixotropic agent and a solder powder, wherein the thixotropic agent is hydrogenated castor oil, bisamide of 12-hydroxystearic acid and diamine. Solder cream using flux which is used in combination. 2. The method according to claim 1, wherein the thixotropic agent is used in an amount of 3 parts by weight per 100 parts by weight of the flux.
The solder cream according to claim 1, wherein a flux is used in an amount of 10 to 10 parts by weight. 3. The solder cream according to claim 1, wherein the weight ratio of bisamide to hydrogenated castor oil is 0.3 to 1.0.