KR20180065583A - Solder paste containing lead free solder composition with high ductility and soldering flux - Google Patents

Abstract

The present invention provides solder paste containing a lead-free solder composition and soldering flux. The lead-free solder composition comprises 0.02-6 wt% of stibium, 0.03-3 wt% of copper, 0.03-8 wt% of bismuth, 55- 68 wt% of indium, and 0.3-8 wt% of silver, 5-11 wt% of magnesium, 0.3-1.45 wt% of scandium, 0.6-1.8 wt% of cerium, and 10-45 wt% of tin. The soldering flux comprises 25-32 wt% of rosin, 5-7 wt% of a mixture of pentane diacid and 2-fluorobenzoic acid as an organic acid activator, 0.2-0.5 wt% of alkylphenol polyoxyethylene as a surfactant, 0.7-0.8 wt% of 1-octyl alcohol as a defoaming agent, 0.5-0.7 wt% of hydroquinone as a stabilizer, and 20-32 wt% of a monoalkyl propylene glycol-based solvent.

Description

[0001] SOLDER PASTE CONTAINING LEAD FREE SOLDER COMPOSITION WITH HIGH DUCTILITY AND SOLDERING FLUX [0002] BACKGROUND OF THE INVENTION [0003]

The present invention relates to a solder paste containing a lead-free solder composition with high ductility and soldering flux.

BACKGROUND OF THE INVENTION Automotive rear windows typically include electrical devices located on glass, such as defrosters. In order to provide an electrical connection to the electrical device, a small area of the metal coating is generally applied to the glass to obtain a metallized surface, which surface is arranged to be electrically connected to the electrical device, May be soldered onto the metallized surface.

In the prior art, an electrical connector is soldered onto a metallized surface on glass using solder containing lead (Pb). However, due to environmental pollution by lead, the use of lead is increasingly limited, and lead-free solders are beginning to be used in soldering applications. For example, universal lead-free solders with a tin (Sn) content as high as 80% or more are used in some industries.

However, since glass is fragile, common tin-free lead-free solders tend to cause cracking of the glass during soldering of the electrical device to glass. Moreover, soldering two materials (e.g., glass and copper) that have substantially different coefficients of thermal expansion (CTE) stresses the solder during cooling of the solder joint or during subsequent temperature excursion. Thus, on the one hand, a solder composition suitable for soldering an electrical device to glass needs to have a melting point (i.e., liquidus temperature) low enough to not cause cracking of the automotive glass during the soldering process, Higher melting points and correspondingly higher processing temperatures increase the side effects of CTE mismatches, resulting in higher stresses on the solder during cooling. As a result, the solder is further required to have good ductility. On the other hand, the melting point of the solder composition needs to be high enough so that the solder is melted during normal use of the vehicle, such as when the car is exposed to sunlight with the window closed and under other extreme harsh environmental conditions .

(Ag) and 0.25 to 0.75% by weight of copper (Cu), 64.35 to 65.65% by weight of indium (In), 29.7 to 30.3% by weight of tin A lead-free solder composition has been conventionally already disclosed (hereinafter referred to as "65 indium solder").

However, indium containing solders typically have a much lower melting point than other solders. For example, 65 indium solder has a solidus temperature of 109 ° C, compared to 160 ° C for lead solder, 127 ° C for liquidus temperature, and 224 ° C for lead solder. Generally, the higher indium content in the solder lowers the solidus temperature of the solder. Some vehicle manufacturers have found that solder joints must be able to withstand elevated temperatures and that solder with an indium content should have a solidus temperature of 120 ° C or higher without degradation and that good ductility at temperatures ranging from -40 ° C to 120 ° C I want to have it.

Further, in soldering a plurality of closely spaced electrical connectors, soldering of the electrical connector will affect the adjacent soldered electrical connector, and therefore the solder must have high stability and ductility, otherwise the adjacent electrical connector Will cause re-melting and cracking.

Soldering flux is an essential additive for soldering. For such solder compositions as desired, a suitable soldering flux is required, so that the solder paste formed by the solder composition and soldering plus can remain sticky during long-term storage, and excess residues can remain in the soldering flux during soldering , And the soldered circuit board can be easily cleaned.

Accordingly, it is an object of the present invention to provide a solder paste containing a lead-free solder composition and a soldering flux, wherein the lead-free solder composition comprises 0.02 wt.% To 6 wt.% Stibium, 0.03 wt. % Of magnesium, 5 wt% to 11 wt% of scandium, 0.3 wt% to 1.45 wt% of scandium, 3 wt% to 3 wt%, bismuth 0.03 wt% to 8 wt%, indium 55 wt% to 68 wt%, silver 0.3 wt% From 0.6 wt% to 1.8 wt% cerium, and from 10 wt% to 45 wt% tin; The soldering flux comprises 25% to 32% by weight of rosin, 5% to 7% by weight of a mixture of diacid and 2-fluorobenzoic acid as an organic acid activator; 0.2% to 0.5% by weight of alkylphenol polyoxyethylene as a surface active agent; 0.7 to 0.8% by weight of 1-octyl alcohol as a defoaming agent; 0.5% to 0.7% by weight of hydroquinone as a stabilizer; And from 20% to 32% by weight of a monoalkylpropylene glycol-based solvent.

The lead-free solder composition of the present invention has a solidus temperature above 120 캜, has good ductility and stability, and is therefore suitable for soldering of electrical connectors on a metallized surface on glass. Furthermore, the soldering flux has a strong wetting power for the lead-free solder; By using the soldering flux, the solder spreads uniformly and the residues generated after welding are soluble in water, so that the printed board has a high insulating resistance after cleaning the soldering flux with water.

The present disclosure will be further illustrated in further detail below in conjunction with some embodiments. It is to be understood that the specific embodiments described herein are for purposes of describing the present disclosure rather than limiting the present disclosure.

The present disclosure provides a solder paste comprising a lead-free solder composition and a soldering flux, which is suitable for soldering an electrical element onto glass. Illustratively, such soldering is required for the manufacture of automotive rear windows, which includes a window defrosting device comprised of an electrically resistive defrosting line embedded in the inner surface of the rear window or deposited on the inner surface. The defrost lines are electrically connected to a pair of electrical contact strips (i.e., an electrical contact surface, also referred to as a buss bar) located on the inner surface of the rear window. The electrical contact strip may be comprised of a conductive coating deposited on the inner surface of the rear window. Typically, the electrical contact strip is formed from a silver-containing material.

To overcome the problems of the prior art, one embodiment of the present invention provides a solder paste containing a lead-free solder composition and a soldering flux, wherein the lead-free solder composition comprises 0.02 wt.% To 6 wt. % Copper, 0.03 wt% to 3 wt%, bismuth 0.03 wt% to 8 wt%, indium 55 wt% to 68 wt%, silver 0.3 wt% to 8 wt%, magnesium 5 wt% to 11 wt%, scandium 0.3 wt % To 1.45 wt%, cerium 0.6 wt% to 1.8 wt%, and tin 10 wt% to 45 wt%. The soldering flux comprises 25% to 32% by weight of rosin, 5% to 7% by weight of a mixture of pentane diacid and 2-fluorobenzoic acid as the organic acid activator; 0.2% to 0.5% by weight of alkylphenol polyoxyethylene as a surface active agent; 0.7 to 0.8% by weight of 1-octyl alcohol as a defoaming agent; 0.5% to 0.7% by weight of hydroquinone as a stabilizer; And from 20% to 32% by weight of a monoalkylpropylene glycol-based solvent.

In an embodiment, the lead-free solder composition comprises scandium and cerium, wherein scandium has the effect of reducing the grain size and raising the recrystallization temperature and enhancing the softness and stability of the solder Cerium, on the other hand, is characterized by a high melting point, high strength and anti-corrosion, which can enhance the strength, high temperature resistance and mode of solder, prevent cracking of the solder joint, The solidus temperature of the composition is increased to within the range of 120 占 폚 to 135 占 폚 and the liquidus temperature of the solder composition is increased to within the range of 130 占 폚 to 145 占 폚.

In some embodiments, the lead-free solder composition may comprise from 1.0 wt% to 1.1 wt%, more preferably 1.05 wt%, scandium.

In some embodiments, the lead-free solder composition may comprise from 0.7 wt% to 0.8 wt%, more preferably 0.75 wt%, of cerium.

In some embodiments, the lead-free solder composition may comprise 3 wt% to 4 wt% antimony and 4 wt% to 5 wt% bismuth.

In some embodiments, the lead-free solder composition may comprise from 6 wt% to 10 wt%, preferably from 7 wt% to 9 wt%, and more preferably 8 wt% of magnesium. In some other embodiments, the lead-free solder composition may comprise from 8% to 9% by weight of magnesium.

The monoalkyl propylene glycol solvent may be butyl propylene triglycol or butyl propylene diglycol and inhibits the reaction between the metal contained in the solder alloy and the activator to prevent formation of a metal salt.

As described above, the lead-free solder composition in the solder paste of the present invention has a solidus temperature in the range of 120 占 폚 to 135 占 폚 and a liquidus temperature in the range of 130 占 폚 to 145 占 폚. The solidus temperature is in fact defined as the temperature at which the alloy begins to melt. At temperatures below the solidus temperature, the components are completely solid without containing the molten phase. The liquidus temperature is the maximum temperature at which the crystal (unfused metal or alloy) can co-exist with the melt. At temperatures above the liquidus temperature, the material is homogeneous and consists only of the melt. The solder processing temperature is several orders of magnitude higher than the liquidus temperature, as determined by the soldering technique.

The solder composition of the present invention does not contain lead and has a higher operating temperature than other solders of the same type, typically about < RTI ID = 0.0 > 105 C. < / RTI > In addition, the solder compositions of the present invention have much better ductility and stability compared to conventional lead-free solder compositions of the prior art.

The combination of bismuth and copper with other elements improves the overall performance of the solder composition, including an expected increase in the operating temperature of the solder and enhanced mechanical performance of the solder under certain conditions.

In some embodiments, the lead-free solder composition may have a solidus temperature in the range of 120 캜 to 135 캜.

In some additional embodiments, the solder composition may have a liquidus temperature ranging from 130 캜 to 145 캜.

In some embodiments, the lead-free solder composition may comprise from 3% to 4% by weight of antimony.

In some embodiments, the lead-free solder composition may comprise from 4 wt% to 5 wt% of bismuth.

The lead-free solder composition of the present invention has a solidus temperature above 120 占 폚, has good ductility and stability, and is therefore suitable for soldering electrical connectors onto a metallized surface on glass.

Now, the crack resistance performance of the solder joint formed by the solder paste of the present invention will be described below with a comparison between the embodiments of the present invention and some comparative examples as shown in Table 1 below.

practice
Form 1 practice
Form 2 practice
Form 3 practice
Form 4 practice
Form 5 Comparative Example 1 Comparative Example 2 content
(weight%) antimony One 2.3 4 4.3 5 4 5 Copper 0.1 0.5 One 1.4 2 One 2 Bismuth 0.5 1.5 3 5 7 3 5 indium 55 57 60 65 68 57 60 silver 0.5 1.5 2.5 4 6 2.5 4 magnesium 5 7 8 9 10 8 9 scandium 0.3 0.6 1.1 1.2 1.45 0.2 1.8 cerium 0.6 0.6 1.0 1.2 1.8 0.05 2.0 Remark 10 20 25 30 40 30 40 crack √ √ √ √ √ x x ductility Good Good Good Good Good Poor Poor fist:
√: No cracks in adjacent solder joints during soldering
x: Cracks occur in adjacent solder joints during soldering

As can be seen from the above table, when the scandium is contained in the solder composition in an amount ranging from 0.3 wt% to 1.45 wt%, cracking of the solder joint formed by the lead-free solder composition of the present invention is prevented . However, when scandium is contained in the solder composition in an amount of less than 0.3 wt% or in an amount of more than 1.45 wt%, cracking resistance of the solder is lowered. Additionally, when cerium is contained in the solder composition in an amount ranging from 0.6 wt% to 1.8 wt%, the solder joint formed by the lead-free solder composition of the present invention has good ductility. However, when cerium is contained in the solder composition in an amount of less than 0.6% by weight or in an amount of more than 1.8% by weight, the softening performance of the solder is lowered.

High temperature storage test

The soft performance of the solder paste of the embodiment of the present invention is tested by the high temperature storage test. In this test, the temperature of the climate controlled chamber was maintained at a constant 120 ° C, and electrical connectors and such electrical connectors were placed in the climate controlled chamber with the metallized surfaces soldered by the inventive solder, Was suspended from the electrical connector for 24 hours. After 24 hours, the electrical connector was pulled with a force of 50 N (at ambient temperature) for 3 seconds by a digital force gauge, and no break of the crack from the electrical connector occurred during this test.

It should be noted that the preferred embodiments of the present disclosure and the applied technical principles are merely as described above. It should be understood by those skilled in the art that the present disclosure is not limited to the specific embodiments described herein. Various apparent changes, rearrangements and alternatives may be resorted to by those skilled in the art without departing from the scope of protection of the present disclosure. Accordingly, although the present disclosure is illustrated in detail by the foregoing embodiments, it is to be understood that the disclosure is not limited solely to the embodiments described above, and may further include other equivalent embodiments without departing from the scope of the present disclosure. have. The scope of the present disclosure is subject to the appended claims.

Claims (5)

A solder paste comprising a lead-free solder composition and a soldering flux,
The lead-free solder composition
0.02 wt% to 6 wt% of stibium;
0.03% to 3% copper by weight;
0.03% to 8% by weight bismuth;
55% to 68% by weight of indium;
From 0.3% to 8% by weight;
From 5% to 11% by weight of magnesium;
0.3% to 1.45% by weight scandium;
0.6% to 1.8% by weight of cerium; And
From 10% to 45% by weight of tin,
The soldering flux
From 25% to 32% by weight of rosin;
5% to 7% by weight of a mixture of diacid and 2-fluorobenzoic acid as an organic acid activator;
0.2% to 0.5% by weight of alkylphenol polyoxyethylene as a surface active agent;
0.7 to 0.8% by weight of 1-octyl alcohol as a defoaming agent;
0.5% to 0.7% by weight of hydroquinone as a stabilizer; And
And 20 wt% to 32 wt% of a monoalkyl propylene glycol-based solvent. The method according to claim 1,
And scandium in an amount of 1.0 wt% to 1.1 wt%. The method according to claim 1,
And 0.7 wt% to 0.8 wt% of cerium. The method according to claim 1,
Wherein the solidus temperature of the lead-free solder composition is in the range of 120 占 폚 to 135 占 폚. The method according to claim 1,
Wherein the monoalkyl propylene glycol solvent is butyl propylene triglycol or butyl propylene diglycol.