CN1555960A

CN1555960A - Tin zinc copper leadless solder alloy

Info

Publication number: CN1555960A
Application number: CNA2004100210398A
Authority: CN
Inventors: 杰赵; 赵杰; 于大全; 马海涛; 韩双起; 黄明亮; 王来
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2004-01-10
Filing date: 2004-01-10
Publication date: 2004-12-22

Abstract

A low-smelting-point lead-free alloy solder contains Zn, Cu, RE chosen from La, Ce, Pr and Nd, Bi and Sn. Its advantages are high wetting power and mechanical performance, no poison and pollution, and low cost.

Description

Tin zinc-copper lead-free solder alloy

Technical field

The invention belongs to the metallic substance technical field, relate to Electronic Packaging braze material technology, specially refer to the lead-free solder alloy that is applicable to the soldering electronic component and does not cause thermal damage.

Background technology

Because traditional tin-lead solder contains the lead element that human body and environment is had very big harm, the development lead-free brazing has become present material scientific worker's a urgent task.The U.S., Japan and other countries were just actively made laws and are forbidden plumbous use, and European Union is according to the instruction of the waste of legislation case electrical and electronic product machinery, will completely forbid the uses of poisonous and harmful element electronic industry such as leaded, cadmium from July 1st, 2006.Thereby, in order to eliminate plumbous pollution, press for unleaded solder and replace the Sn-Pb solder and be applied in the Electronic Packaging welding technique.

In order to make the lead-free solder alloy composition satisfy relevant laws and regulations requirement, and make solder alloy have excellent mechanical property and brazed joint has higher reliability, solder alloy must have appropriate melting point, good wettability, component does not contain poisonous, hazardous property element, the feed rate abundance can satisfy the requirement of industrialization, alloy structure good stability, non-corrosiveness etc.In the binary and multicomponent alloy system of current research, extremely brazed joint research is more for Sn-Ag, Sn-Bi-Ag, Sn-Ag-Cu solder, has application promise in clinical practice.But these alloys are very expensive, are about 3 times of tinsel price.

The Sn-9Zn alloy has good and economic and mechanical property, but the Zn element has the chemical property and the metallurgy of living and dialling, and makes the wettability of this alloy and erosion resistance very poor, has greatly influenced application.And, contain thick β-Sn crystal grain in the Sn-9Zn alloy structure, because wettability difference brazed joint bonding strength is also lower.In recent years, in order to improve the performance of Sn-9Zn alloy, the investigator adds In, Bi, Al and rare earth element etc. in the alloy to as alloy element, but effect is remarkable inadequately.1198117) etc. for example, U.S. patent of invention US6488888, US6440288, US5017738 and thousand live the Chinese invention patent (publication number: added multiple element and improve performance in the Sn-Zn alloy of commercial firm's application.Wherein the addition of Cu is all less than 3%.Yet,, can obviously improve its wettability if in the Sn-9Zn system, add the Cu element of 3-10% according to our current research result.Its reason is to have only the interpolation of Cu just can make Zn form more stable Cu-Zn compound above 3%, has greatly reduced the activity of Zn element; Further, this solder has good mechanical performance and reliability.Its tensile strength is greater than 50Mpa, though plasticity descends, but still has unit elongation and relative reduction in area more than 15%.Can satisfy the mechanical property requirements of solder fully.

Summary of the invention

The objective of the invention is, a kind of tin zinc-copper lead-free brazing is provided,, its wettability, erosion resistance and mechanical property are further improved, thereby can be widely used in the middle of the Electronic Packaging to solve the problem that present restriction red brass exists.

More specifically purpose of the present invention provides the lead-free solder alloy with following character:

1) has good weldability;

2) brazed joint of Xing Chenging has sufficiently high bonding strength, and the brazed joint structure stability is good;

3) can carry out soldering with soldering bit;

4) extremely low cost.

Technical scheme of the present invention is, added the Cu of 3.05～10 weight % in the Sn-Zn alloy,, one or more among optional simultaneously Bi, the trace rare-earth element RE that contains 0.2～2 weight % (by La, Ce, Pr, one or more among the Nd are elementary composition).

The solder alloy composition according to following reason is: the adding of Cu element makes that rich Zn is transformed into Cu-Znization and thing mutually in the alloy, greatly reduced the activity of Zn element, make that the problem of oxidation of Zn is resolved in brazing process, reduced the surface tension of liquid phase, thereby significantly improved wettability.

The trace mixed rare-earth elements has suppressed thick β-Sn crystal grain and has generated, and makes the obvious refinement of alloy structure, and then has improved the mechanical property of alloy, and the adding of rare earth element simultaneously significantly improves the wettability of alloy.

Bi improves wettability, the reduction fusing point of alloy as alloy element

Effect of the present invention and benefit are, because Cu, RE, the adding of Bi alloy element makes solder alloy wettability, mechanical property better, and fusing point is suitable, low price, can overcome the weakness of Sn-Zn alloy, can be widely used in electronic industry, household electrical appliances especially, the unleaded demand in fields such as automobile.

Description of drawings

Fig. 1 be the wetting angle of (Sn-9Zn)-xCu with Cu content synoptic diagram, the brazing flux of use is the active brazing flux of RMA rosin, brazing temperature is 265 ℃.

Embodiment

Be described in detail the specific embodiment of the present invention and embodiment below in conjunction with technical scheme.The chemical ingredients (%) of tin zinc-copper lead-free brazing of the present invention is as follows:

1. (5～10) Zn; (3.05～10) Cu, surplus is that Sn and unavoidable impurities are formed;

2. (5～10) Zn; (0.05～0.5) RE; (3.05～10) Cu, surplus is that Sn and unavoidable impurities are formed;

3. (5～10) Zn; (0.2～2) Bi, (3.05～10) Cu, surplus is that Sn and unavoidable impurities are formed.

Above-mentioned raw material of proportionately distributing is put into the vacuum for industrial use induction furnace smelt, under normal pressure, 600 ℃ of temperature are incubated 4～6 hours, and cast can obtain welding flux alloy. and produce solder powder by spraying, add brazing flux, just obtain soldering paste.

Embodiment:

Choose following chemical components (%): (7～9) Zn; (0.05～0.15) RE; (0.5～2) Bi; (4～6) Cu, surplus is Sn.Above-mentioned raw material of proportionately distributing is put into the vacuum for industrial use induction furnace smelt, under normal pressure, 600 ℃ of temperature are incubated 4～6 hours, and cast can obtain welding flux alloy, produces solder powder by spraying, adds brazing flux, just obtains soldering paste.Can be used for reflow welding.

Claims

1. tin zinc-copper lead-free solder alloy is characterized in that containing the Zn of 5～10 weight %, the Cu of 3.05～10 weight %, and all the other are Sn.

2. a kind of tin zinc-copper lead-free solder alloy according to claim 1 is characterized in that containing the rare earth element of 0.05～0.5 weight %, and rare earth element comprises La, Ce, Pr, one or more elements among the Nd.

3. a kind of tin zinc-copper lead-free solder alloy according to claim 1 is characterized in that containing the Bi of 0.2～2 weight %.