JPH07290277A - Flux - Google Patents

Abstract

PURPOSE:To reinforce tacking force and to prevent generation of cross balls of parts at the time of soldering by forming the flux of cream solder of glycol diethers. CONSTITUTION:The glycol diethers expressed by the formula are used as the flux. In the formula, R1 and R2 are 1 to 36C hydrocarbons which may be the same or different and more particularly preferably 1 to 8C alkyl groups which may have branches; the total carbon atoms of R1, R3 are preferably from to 16. R2 is a hydrogen atom or 1 to 8C hydrocarbon group and is more particularly preferably an alkyl group; (n) is l to 6 and more preferably 1 to 3. The cream solder is prepd. by mixing solder powder together with a resin, activator, viscosity control agent, thickener, defoaming agent, plasticizer, etc., with such glycol diethers. The compounding ratio of the glycol diethers in such a case is 10 to 99% of the total amt. of the flux and is 10 to 50% in the case of the flux of the cream solder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering flux and a cream solder containing the flux.

[0002]

Fluxes used for soldering are usually resins mainly composed of rosins, active agents for removing metal oxide films formed on the surfaces of metal to be joined such as amine salts and acids, and these It contains a solvent that dissolves. Recently, soldering of very small parts such as electronic wiring parts is required, and as various soldering techniques for that have been developed, the performance required for flux and solder has also become very sophisticated. . In particular, recently, a technique has been widely adopted in which solder is cream-shaped and the solder is precisely screen-printed on the joint portion of the printed wiring, and the cream solder is required to have printing characteristics for that purpose.

Among such characteristics, it is particularly required that the viscosity change with time is small, the tacking force is large and long, continuous printing can be lengthened, and the component lateral balls are not generated. Further, it is desirable that the composition be such that it can be easily adjusted according to the printing characteristics and the drying time. Further, as the metals to be joined are diversified, the types of activators are also diversified, and it may be necessary to use a large amount in some cases. Therefore, solubility in various activators is required.

In order to solve these problems, it has been attempted in the past to change the types and combinations of resins and activators, select a solvent, add various additives for adjusting viscosity, and the like. There is. However, there has not been obtained a cream solder capable of obtaining good results with respect to all the above problems. In particular, no proposal has been made to solve the above problems by using glycol diethers such as those used in the present invention.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a flux and a cream solder which can achieve good results with respect to the above problems.

[0006]

The present invention has the formula: R ₁ --O--
(CH ₂ —CH (R ₂ )) n—O—R ₃ (In the formula, R ₁ and R ₃ may be the same or different and are a hydrocarbon group having 1 to 36 carbon atoms, and R ₂ is a hydrogen atom or a carbon number. The present invention relates to a flux containing a hydrocarbon group of 1 to 8 and a glycol diether represented by (n represents a number of 1 to 6) and a cream solder containing the flux.

In the glycol diethers used in the present invention, R ₁ and R ₃ have a saturated or unsaturated aliphatic hydrocarbon group which may have a branch, an alicyclic hydrocarbon group, or a substituent. Are aromatic hydrocarbon groups, aliphatic hydrocarbon groups which may have a substituent, etc., and have 1 to 3 carbon atoms.
6, more preferably 1 to 18, and particularly preferably an optionally branched alkyl group having 1 to 8 carbon atoms. The total carbon number of both is preferably 4 to 16. As the total carbon number of both decreases, the hygroscopicity increases, and the stability over time of the cream solder decreases. From the viewpoint of paste stability, either R ₁ or R ₃ has at least 6 carbon atoms. Is preferred. On the other hand, as the total carbon number of R ₁ and R ₃ increases, the solubility of the ionic activator blended in the flux decreases. The hydrophobicity of the flux rises, the change in viscosity over time is reduced, and link printing is improved.

R ₂ is hydrogen or has 1 to 8 carbon atoms, especially 1
And the alkyl group is particularly preferable. As the carbon number increases, the solubility of the activator tends to decrease.

N is 1 to 6, preferably 1 to 3. When the n number is large, the hygroscopicity is high and the stability of the cream solder is reduced. Further, the viscosity becomes high and the application range becomes narrow.

Specific examples of glycol diethers particularly suitable for the present invention include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether,
Diethylene glycol dibutyl ether, diethylene glycol ethyl butyl ether, triethylene glycol dibutyl ether, tetraethylene glycol dibutyl ether, diethylene glycol dioctyl ether, diethylene glycol di-2-ethylhexyl ether, dipropylene glycol diethyl ether, dipropylene glycol dimethyl ether, diethylene glycol 2-ethylhexyl ether, diethylene glycol butyl 2-ethylhexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol dibutyl ether, tripropylene isopropyl butyl ether, tripropylene glycol isopropyl ethyl ether, tetrapro Glycol dipropyl ether, and the like.

The content of glycol diethers is 10 to 99% of the total flux, and the flux of cream solder is 10 to 50%.

The flux or cream solder of the present invention may be blended with other solvents conventionally blended therein. Such solvents include organic solvents, especially alcohols, glycols, esters, ethers,
Examples thereof include glycol ethers, terpenes, alicyclic hydrocarbons, aliphatic hydrocarbons, aromatic hydrocarbons, etc., preferably having a boiling point of 180 ° C. or higher, particularly 260 ° C.
It is preferable that the resin has a low hygroscopic property at a temperature of 300 to 300 ° C. and can well dissolve resins and chelates.

Specific examples of particularly preferable solvents for the present invention include glycols such as ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol, mono- or diethers thereof with lower alcohols, mono- or diesters, cyclic ethers. , Especially crown ethers, glycerin, pentaerythritol, trimethylolpropane, their esters and the like. Since the solvent of the present invention has a low viscosity and a low latent heat of vaporization, it relatively quickly vaporizes. Therefore, in order to prolong the tacking time, a substance having a relatively high boiling point is preferable.

The cream solder of the present invention is characterized in that it has a strong tacking force and does not generate a lateral ball of a component. This is probably because the latent heat of vaporization of the solvent is small and the viscosity is low. Therefore, the mixing of the solvent, especially the mixing of the materials having inferiority in the above items, reduces the effect. However, other solvents can be added for the purpose of improving the solubility of the ionic activator, and mixing of the solvents does not limit the present invention.

In the cream solder of the present invention, the above flux is mixed with solder powder. Examples of the resin include rosins such as rosin, polymerized rosin, disproportionated rosin, hydrogenated rosin, and maleated rosin.

Examples of the activator include hydrogen halide salts of nitrogen-containing bases such as cyclohexylamine, hydrogen bromide, amino acids, organic acids such as glutamic acid and adipic acid.

Viscosity modifiers are those having the property of being dissolved or dispersed in the above-mentioned solvents to increase the viscosity or imparting thixotropic properties. Specifically, for example, high molecular weight polyethylene glycol, polypropylene Thickeners soluble in organic solvents such as glycol and ethyl cellulose, hardened castor oil, fats and oils such as coconut oil,
Waxes of higher alcohols and higher fatty acids, saturated higher fatty acids or alcohols, esters of higher alcohols and higher fatty acids, amides or bisamides of higher fatty acids, carnauba wax, acacia gum, tragacanth gum, guar gum, locust bean gum, Natural or semi-synthetic gums such as arabinogalactotone, karaya gum, iris moss, gelatin, sodium alginate, propylene glycol alginate, synthetic resins,
Examples include low molecular weight phenol formaldehyde resin and low molecular weight polyethylene wax.

These viscosity modifiers are used in an amount of 0.01 to 10% by weight of the total amount of flux, preferably a viscosity of 50,000 to 1,000,000 cps at 23 ° C. when adjusted to cream solder.
More preferably, it is used in the range of 100,000 to 800,000 cps.

The amount of the resin used is 1 to 70% by weight, more preferably 10 to 70% by weight, based on the total amount of the flux. The amount of the solvent used is 10 to 99% by weight, more preferably 20 to 99% by weight, based on the total amount of the flux. The amount of activator is 0 to 10% by weight of the total flux, more preferably 0 to 2% by weight.

The thickener may be blended appropriately so that the viscosity of the cream solder becomes the optimum working viscosity. Usually 10 at room temperature
Adjust from 10,000 cps to 1 million cps.

The defoaming agent may be a silicone type defoaming agent, an alcohol type defoaming agent such as 2-ethylhexanol or the like.
Examples thereof include a monomer and lauryl alcohol.

Examples of the antioxidant include 2,6-di-t-butyl-p-cresol and the like.

Examples of the plasticizer include esters such as dioctyl phthalate and diethyl phthalate. The cream solder contains solder powder in addition to the above components. The solder powder is a tin-, lead-, or zinc-based solder, and also contains silver, antimony, cadmium, copper, phosphorus, and the like.

The particle size of the solder powder is 5 μm to 50 μm, more preferably 20 μm to 40 μm. The amount of the solder powder used is 70% by weight to 94% by weight, and more preferably 85% by weight to 91% by weight based on the total amount of the cream solder. Example 1 The flux was adjusted according to the formulation shown in Table 1.

[0025]

[Table 1] Solder powder (tin / lead = 63
/ 37 weight ratio, average particle size 20 μm)
The mixture was mixed for a minute and made uniform to obtain cream solder.

The following characteristics were evaluated for this cream solder. Evaluation method (1) Tacking time (new JIS proposal) Paste is printed at 6.5Φ and thickness of 200μm, and the temperature is 2
It is placed in an environment of 5 ° C. and a humidity of 50%, and after a lapse of a certain period of time, the tackiness is measured under the following conditions with a tacking tester TAC-II manufactured by Lesca. Probe diameter: 5.1Φ Pushing speed: 120 mm / min Pulling speed: 600 mm / min Pressing force: 50 gf Pressurizing time: 0.2 sec ◎: 80 h or more at 8 h ○: 80 g at 4 h ×: 80 g at 4 h (2 ) Component lateral ball test method Chip lateral solder ball test substrate (1608 and 2
The paste is printed to a thickness of 200 μm on 175 125 chip resistors can be mounted) to mount the chip resistors. Reflow under standard conditions and check the solder balls that are formed on the side of the chip. ⊚: Ball generation rate is 0.01% or less ◯: Ball generation rate is 1% or less ×: Ball generation rate is more than 1% (3) Stability over time ◎: Room temperature 3 weeks Viscosity increase rate of 5% or less ○: Viscosity increase rate of 3 weeks at room temperature is 10% or less ×: Viscosity increase rate of room temperature of 3 weeks exceeds 10% (4) Continuous printability ◎: Continuous printing 8 h possible ○: Continuous printing 4h possible ×: Continuous printing 4h impossible (5) Oxide residue after leaving ◎: No oxide residue occurs even after leaving for 8h ○: No oxide residue occurs even after leaving for 4h ×: Even after leaving for 4h Generated by oxide residue

A similar test was carried out on a cream solder which did not use glycol diether as a solvent (comparative example). Table 1 shows the characteristics of the cream solder.

[0028]

The cream solder of the present invention does not generate lateral balls of parts, is excellent in stability over time, and has no change in viscosity over time. High tacking power and long tacking time. In addition, continuous printing is possible for a long time, and there is little oxide residue even if left for a long time. Further, there are many kinds of glycol diethers, and there are advantages such as selection of good solvents for various activators, and wide selection range of required boiling points.

Claims (2)

[Claims] 1. The formula: R ₁ --O-(CH ₂ --CH (R ₂ )) n--
O—R ₃ (wherein, R ₁ and R ₃ may be the same or different, and are a hydrocarbon group having 1 to 36 carbon atoms, R ₂ is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and n is 1 A flux containing a glycol diether represented by 2. A cream solder containing the flux of claim 1 and solder powder.