JPS60148692A - Pb base high melting solder - Google Patents

Abstract

PURPOSE:To increase solidus line temp. without decreasing adhesion strength and to improve reliability by compounding Sn, Cu and Pb which are limited in compsn. ratio and melting Pb high melting solder. CONSTITUTION:Pb high melting solder consists, by weight, of 0.5-5% Sn, 1.5- 5% Cu and the balance Pb. The reason for limiting the solder compsn. is as follows: at least >=0.5w% Sn is required as an Sn-Cu base alloy is used for adding Cu and if the content of Sn is <0.5w%, the high melting base alloy contg. much Cu is eventually used and heating of Pb to a high temp. is necessitated and therefore problems such as oxidation, evaporation, etc. arise, thus making the production of solder difficult. If the content. of Cu is <1.5w%, the effect is not enough and when the content exceeds 5w%, the increased viscosity of the solder and the decreased fluidity and solderability are resulted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inexpensive Pb-based high melting point solder having a solidus temperature of 310° C. or higher and used for various solder joints, semiconductor die bonding, etc.

Conventionally, P was used for various solder joints, semiconductor die bonding, etc.
High melting point solders such as B-based, Sn-based, Cd-containing, and noble metal-based solders are used.

Pb-based solders include Pb-8n, Pb-In, or these with AQ added to high-melting point solders, Sn-based solders include So-8b, 8n-Ag, So-Au, etc., and Cd-containing solders include 5n. -Cd, Sn-
High melting point solders such as Zn-Cd are known, and high melting point solders such as AU-8i are known as noble metal bases.

In recent years, with the increasing density of semiconductors, there has been a demand for inexpensive high melting point solder with a common mode temperature of 300°C or higher from the viewpoint of cost and reliability, and semiconductor substrates are now coated with N1 plating. Therefore, in terms of soldering to N1, it is desired that the solidus temperature and liquidus temperature be close to each other from the viewpoint of performance and workability. However, the above-mentioned Pb-based and Sn-based high melting point solders both have a low melting temperature and a maximum solidus temperature of around 300°C, and the solidus temperature of the Cd-containing high melting point solder increases with the addition of Cd. , CD is a toxic substance, so its use is restricted.

In addition, noble metal-based high melting point solders have a high solidus temperature, for example, AU-2wt%S1 alloy (hereinafter wt% is simply abbreviated as %) has a solidus temperature of 370°C and a liquidus temperature of 390°C. Because it contains a large amount of precious metals, it is extremely expensive.

In view of this, as a result of various studies, the present invention has discovered that by adding Cu to Pb-8n alloy solder, the in-phase temperature and liquidus temperature can be increased without reducing soldering properties, As a result of further investigation, the solidus temperature was 3
We have developed an inexpensive Pb-based high melting point solder that has a temperature of 10°C or higher, with 5nO 15-5%, Cu 1.5-5%, and the remainder p.
It is characterized by consisting of b.

However, the reason why the solder composition is limited as described above in the present invention is as follows.

That is, when the Sn content is limited to 0.5% to 5%, sn
is an additive element for soldering, but C
Since a 5n-Cu master alloy is used for the addition of u, it is necessary to make the Sn content at least 0.5% or more, and if the Sn content is 0.
．． If it is less than 5%, a high melting point master alloy with a high Cu content will be used, and Pb will also have to be heated to a high temperature (800°C), which will cause problems such as oxidation and evaporation, making solder production difficult. . On the other hand, if the Sn content exceeds 5%, the solidus temperature of the solder will drop significantly.

Further, the reason why the Cu content is limited to 1.5 to 5% is that although the addition of Cu has the effect of increasing the solidus temperature and suppressing the copper cracking phenomenon, the Cu content is limited to 1.5% to 5%. This is because if it is less than 5%, the effect is not sufficient, and if it exceeds 5%, the viscosity of the solder increases and the fluidity and soldering properties are significantly reduced.

The solder of the present invention is manufactured using a 5n-Cu master alloy, Pb alone, and S.
It is sufficient to mix n alone into a desired solder composition, melt and cast it in the atmosphere, and process it according to a conventional method. In addition, for semiconductor die bonding, as shown in FIG. )
A molten metal (4) of a desired composition is inserted into the molten metal, the surface of the molten metal is pressurized in the direction of the arrow, and the molten metal (4) is ejected from the nozzle (3) onto the surface of the roll (1) through the nozzle (3). It is preferable to use molded solder which is made into a tape-shaped solder (5) by a molten metal quenching method in which it is directly solidified into a tape-shaped form, and which is then subjected to cutting, punching, bending, etc. In particular, solder produced by the molten metal quenching method has a structure in which Cu is finely dispersed.
Soldering in a short time will not result in large non-uniform compounds such as Sn Cu.

The present invention will be described below with reference to Examples.

A high-melting point solder having the composition shown in Table 1 was mixed and melted using a 5n-Cu mother alloy, Pb alone, and Sn alone, and a tape-like material with a medium size of 12# and a thickness of 50 μm was made by the molten metal quenching method shown in Figure 1. A PB-based high melting point solder was manufactured.

The solidus temperature and liquidus temperature of these were measured by thermal analysis. The results are shown in Table 1.

Note that high melting point solder having a Cu content exceeding 5% could not be jetted out from the nozzle due to decreased fluidity, and it was not possible to produce tape-shaped high melting point solder by the molten metal quenching method. Moreover, adhesive strength was measured by a conventional method.

5- Table 1 No. by solder, composition (wt%) Solidus temperature
Liquidus temperature Adhesive force Sn Cup pb (℃) (
℃) (K9/d>Inventive solder 10.5 2.0
Remaining 329 335 0.3~0.4N 2 1.0
2. On 327 334/J 3 2,0 1.5
,, 322 328 0.32~0.4// 4 2
．． 0 2,0 # 324 330 0.3~0.4〃
5 2.0 3,0 ,, 326 332 0.35
~0.45II6 2.0 4. On 328 333
0.3~0.4〃7 2.0 5,0,, 329
334 0.28-0.35n 8 3. Q3. O
n 325 331 0.32-0.4TI 9 4.
0 4. OII 326 332 0.3~0.4〃1
0 5.0 2.0 ,, 313 321yt 11
5,0' 3.0 /7 324 331# 12
5.0 5.0 //326 335 comparison solder 13
5.0-. 7 300 0.3 to 0.4 As is clear from Table 1, the in-phase line temperature of all of the solder Nos. 1 to 12 of the present invention increases without decreasing the adhesive strength. On the other hand, comparative solder No. 13 that does not contain Cu
It can be seen that the common mode line temperature is as low as 300°C.

In this way, the high melting point solder of the present invention has a common phase temperature of 310°C.
With the above-mentioned inexpensive Pb-based products, the chip remains stable even during thermocompression die bonding (capillary temperature of about 350°C) using -0- gold wire.
This has the remarkable effect of improving workability and reliability in die bonding of semiconductors.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a molten metal quenching method for manufacturing a solder tape of the present invention. 1. Cooling roll 2, Crucible 3, Nozzle 4, Molten metal 5, Tape 7 - Figure 1, page 1 continued 0 Inventor Shigeaki Nishikawa 465, Tokyo Parts Industry Ward 2 Central Research Laboratory -

Claims (1)

[Claims] Sn 0.5-5'wt%, Cu 1.5-5wt%
, the balance is Pb-based high melting point solder.