JP2003205388A - Method of producing lead-free solder for package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the failure that, in tin-bismuth (Sn-Bi) solder as lead-free solder presently substituted for lead-containing solder, the precipitation of bismuth occurs in a process of flowing solder, so that the solder is liable to drop. <P>SOLUTION: The method of producing lead-free solder for a package is performed by the following steps: (a) a mixed metal produced by a combination system of five kinds of bismuth-free tin based lead-free solder, e.g. of 7 to 11 wt.% Zn, and 0.1 to 0.5 wt.% Co, and the balance Sn, or of 7 to 11 wt.% Zn, and 0.1 to 0.5 wt.% Al, and the balance Sn is provided; (b) the above mixed metal is fused at ≤350°C by utilizing a light frequency furnace to form into a cast matrix of required dimensions; (c) the matrix is subjected to homogenizing treatment at 180 to 240°C for 30 to 240 min; and (d) the matrix after the homogenizing is directly drawn, and is formed as a lead-free solder wire rod, or a spherical product. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lead-free solder manufacturing method for packages. INDUSTRIAL APPLICABILITY The lead-free solder manufacturing method for a package of the present invention is an excellent manufacturing method from the viewpoint of environmental protection at the same time as firmly packaging the contacts of an integrated circuit (IC).

[0002]

2. Description of the Related Art Semiconductor technology is advancing day by day.
In addition to rapid progress in functionality, electronic products are required to continuously improve the semiconductor manufacturing process and material technology due to the global awareness of environmental protection. With the constant threat of the Earth's living environment, the industry is unaware of the problem of lead pollution from electronic products discarded in the last decade. In some countries, legislation has been banned on products containing lead (starting in 2004 in EU countries) to promote environmental protection. Conventional integrated circuit (IC) contact packaging materials that use lead-containing solder have a typical heat resistance temperature of electronic components of 220 ° C, so the solder material used has a heat resistance temperature lower than 220 ° C. I had to. Therefore, up to now, the heat resistant temperature of the solder material has been set to 220 ° C. or lower depending on the mixing ratio of the tin-lead components. See Figure 1. 63% tin and 37 lead
%, The melting temperature which is the closest to both tin and lead is about 183 ° C., which is lower than 220 ° C. which is the upper limit of the heat resistant temperature of electronic parts. Therefore, until now, solder containing lead has been used as an adhesive package material for contacts of integrated circuits (ICs). Regarding the inability to use lead-containing solders for electronic products, the current melting temperature of lead-containing solders is about 183 ° C, which is the lowest due to the mixing of tin with other lead-free alloys. The melting points of all the materials are relatively higher than 183 ° C. Therefore, lead-free solder packaging materials can only be used with higher performance. Therefore, the maximum heat resistant temperature of the current parts reaches 250 ° C at the maximum. Therefore, the melting temperature of the solder containing no lead component is set to 210 ° C (about 40 ° C lower than the heat resistant temperature of the component). As a lead-free solder that directly replaces the existing leaded solder,
Most integrated circuit (IC) manufacturers are tin bismuth (S
n-Bi) Solder is selected. It provides a high degree of wetting, is easy to use and does not produce fine lines, so it does not short circuit. However, in the process of flowing the solder, precipitation of bismuth is easily caused by life-off (life-o).
ff) phenomenon occurs, the solder drops off, and manufacturers are reluctant to use bismuth materials.

[0003]

[Problems to be Solved by the Invention] Providing a mixed metal produced by five kinds of combination methods, melting the above-mentioned mixed metal at a temperature of 350 ° C. or less by using a high frequency furnace, and performing rapid cooling to make it necessary. Use a cast metal of a large size. The metal is homogenized at 180 to 240 ° C. for 30 to 240 minutes. The homogenized metal is directly drawn and formed as a lead-free solder wire or spherical product.

[0004]

DETAILED DESCRIPTION OF THE INVENTION Please refer to FIG. This is performed by the following steps in the manufacturing process of the lead-free solder of the present invention. (A) Zinc (Zn) content 7 to 11 wt%, cobalt (Co) content 0.1 to 0.5 wt%, and the balance tin (S)
n) or zinc (Zn) content 7 to 11 wt%,
Cobalt (Co) content 0.1 to 0.5 wt%, phosphorus (P) content 0.005 to 0.05 wt%, balance tin (Sn) or zinc (Zn) content 7 to 11 wt
%, Aluminum (Al) content 0.1 to 0.5 wt%, and the balance tin (Sn) or zinc (Zn) content 7 to 11
wt%, aluminum (Al) content 0.1 to 0.5 wt%,
Phosphorus (P) content of 0.005 to 0.05 wt%, balance of tin (Sn) or indium (In) content of 10
~ 15wt%, cobalt (Co) content 0.1-0.5
A mixed metal manufactured by five types of combination methods, such as wt% and the balance being tin (Sn), is provided. (B) Using a high-frequency furnace, the above-mentioned mixed metal is melted at a temperature of 350 ° C. or lower, and is rapidly cooled to obtain a cast metal in a required size. (C) The metal is homogenized at 180 to 240 ° C. for 30 to 240 minutes to make the surface of the metal smooth and flat so that there are no dents or holes. (D) The homogenized base metal is directly stretched to form a lead-free solder wire or a spherical product. In the description of the manufacturing process, in the present invention, the lead-free solder is manufactured using the above-mentioned five kinds of mixed metals. Naturally, the characteristics of the material also change due to the combination of different metals. Among the many types of metals mentioned above, the first possible requirement is the melting temperature (Melting Temp) of the mixed metal.
In p), it should not be higher than 210 ° C. Reference values obtained by experiments for lead-free solders made of the above-mentioned five kinds of mixed metals are shown below. (I) Zinc (Zn) content 7 to 11 wt%, cobalt (Co) content 0.1 to 0.5 wt%, and the balance tin (S)
n) Lead-free solder made of a mixed metal such as the above has a solidification temperature of about 199 ° C., a liquefaction temperature of about 200 ° C., and a melting temperature (Melting Temp) of about 199 to 200 ° C.
Is in between. Tensile Strength (Tensil Strength
th) is 6.2 kgf / mm ² _{, and the} extension rate (Elonga)
It is 68%. (II) Zinc (Zn) content 7 to 11 wt%, Cobalt (Co) content 0.1 to 0.5 wt%, Phosphorus (P) content 0.005 to 0.05 wt%, and the balance Tin (Sn) The lead-free solder produced from the equal mixed metal has a small amount of phosphorus (P) component added to the mixed metal of the item (I). Its tensile strength and elongation are low, and its melting temperature (Melting Temp) is between about 199 and 200 ° C., which is the same as the melting temperature of the mixed metal of (I). Tensile Strength is 5.8
kgf / mm ² _, extension rate (Elongation) 60
%. (III) Zinc (Zn) content 7 to 11 wt%, aluminum (Al) content 0.1 to 0.5 wt%, the balance is tin (S)
n) Lead-free solder made of a mixed metal such as aluminum uses aluminum (Al), which is low in cost, because the material properties of cobalt (Co) and aluminum (Al) are similar. The solidification temperature is about 196 ° C., the liquefaction temperature is about 197 ° C., and the melting temperature (Melting Temp) is about 199 to 200.
Between ℃. Tensile Strength
ngth) is 6.2 kgf / mm 2 _{, and the} extension ratio (Elong
ation) 67%. (IV) Zinc (Zn) content 7-11 wt%, aluminum (A
l) Content 0.1-0.5 wt%, phosphorus (P) content 0.005-0.05 wt%, the balance solder made of a mixed metal such as tin (Sn), the term (III) A small amount of phosphorus (P) component is added to the mixed metal of. Its tensile strength and elongation are low and its melting temperature (M
The melting temperature is about 196 to 197 ° C., which is the same as the melting temperature of the mixed metal of (III). Tensile Strength is 5.8
kgf / mm ² _, extension rate (Elongation) 59
%. (V) Indium (In) content is 10 to 15 wt%, cobalt (Co) content is 0.1 to 0.5 wt%, and the rest is made of a mixed metal such as tin (Sn). Ingredients are added, and zinc (Z
It is possible to replace n). Its melting temperature is rather low, solid temperature is about 183 ° C, liquefaction temperature is about 195.
℃, Melting Temp is about 18
It is between 3 and 195 ° C. Correspondingly, the extension rate is slightly inferior and the Tensil Strength (Tensil Strength)
h) is 5.7 kgf / mm ² _, extension rate (Elongat)
ion) 33%. By selecting an appropriate mixed metal component from (I) to (V), a lead-free solder having necessary material characteristics can be manufactured.

[0005]

Industrial Applicability All products manufactured by the lead-free soldering method for a package of the present invention have oxidation resistance.
The welding temperature is lower than 250 ° C, the liquefaction and solidification temperatures of the solder material are close, and the melting temperature is close to the solder material of 63% tin and 37% lead. The strength is 5 kgf / mm ² or more, and the extension ratio is 10% or more. Its soldering performance is very good and perfectly meets the needs of solder material for packaging. In addition, since the lead-free solder manufacturing method is used in the manufacturing process and the lead-free manufacturing process lowers the inspection and repair rate of the entire equipment, the equipment cost during manufacturing can be kept low and the industrial utility value is high. The lead-free solder manufacturing method for a package of the present invention is characterized in that the manufactured lead-free solder has high adhesiveness at an integrated circuit contact and also meets environmental protection conditions.

[Brief description of drawings]

FIG. 1 is a comparison table of melting temperatures obtained by experiments with respect to a conventional tin-lead content.

FIG. 2 is a flowchart showing steps of the lead-free solder manufacturing method of the present invention.

Claims (3)

[Claims] 1. A (a) zinc (Zn) content of 7 to 11 wt.
%, Cobalt (Co) content 0.1 to 0.5 wt%, the rest is tin (Sn), or zinc (Zn) content 7 to 11 wt%, cobalt (Co) content 0.1 to 0.5 wt% %, Phosphorus (P) content is 0.005 to 0.05 wt%, the rest is tin (Sn), or zinc (Zn) content is 7 to 11 wt%, aluminum (Al) content is 0.1 to 0.5 wt% %, The rest is tin (S
n), or zinc (Zn) content 7 to 11 wt%, aluminum (Al) content 0.1 to 0.5 wt%, phosphorus (P) content 0.005 to 0.05 wt%, and the balance tin ( Sn) or indium (In) content 10 to 15 wt
%, Cobalt (Co) content 0.1 to 0.5 wt%, the rest is tin (Sn), etc. to provide a mixed metal produced by a combination method, and (b) use a high frequency furnace. Melted the above-mentioned mixed metal at a temperature of 350 ° C. or lower, and made a cast metal ingot of a required size by rapid cooling. (C) The metal was homogenized at 180 to 240 ° C. for 30 to 240 minutes. (D) A lead-free solder manufacturing method for a package, which is performed according to the steps of directly drawing the homogenized metal and forming it as a lead-free solder wire or a spherical product. 2. A lead-free solder product manufactured by steps (a) to (d), having a liquefaction and solidification temperature of 183 to 200 ° C. and a welding temperature of 250.
The lead-free solder manufacturing method for a package according to claim 1, which is characterized in that the temperature is lower than 0 ° C. to make the adhesion of integrated circuit (IC) contacts firm. 3. A lead-free solder product manufactured by steps (a) to (d), having a stencil strength of 5.7 to 6.2 kgf / mm ² and an extension rate of 33 to 68.
%, The extension ratio is larger than 10%, and the lead-free solder manufacturing method for a package according to claim 1, wherein the lead-free solder has further excellent soldering performance.