CN101575680A

CN101575680A - Lead-free solder alloy

Info

Publication number: CN101575680A
Application number: CNA2008100279851A
Authority: CN
Inventors: 项羽
Original assignee: Mitac Computer Shunde Ltd
Current assignee: Mitac Computer Shunde Ltd; Shunda Computer Factory Co Ltd
Priority date: 2008-05-09
Filing date: 2008-05-09
Publication date: 2009-11-11

Abstract

The invention provides a lead-free solder alloy mainly comprising 99-99.96 percent of stannum, 0.3-0.9 percent of copper, 0.01-0.06 percent of nickel and 0.003-0.01 percent of bismuth. The lead-free solder alloy not only solves the problem that copper foil on an electronic assembly is easy to corrode the lead-free solder alloy in the stannum spraying process to cause the solder alloy copper content to rise, but also effectively lowers the cost.

Description

Leadless welding alloy

Technical field

The present invention relates to a kind of leadless welding alloy, relate in particular to a kind of leadless welding alloy that is used for the electronic package welding.

Background technology

Traditional welding flux alloy that is used for electron and electrician production such as Sn-Pb alloy include not labile metallic lead, not only cause pollution easily, and be difficult for after being absorbed by the body excreting, human health is impacted environment, therefore, the manufacturing of alternative lead-free solder is arisen at the historic moment.

At Sn-Ag is in the alloy, the Sn-3.5Ag alloy is an eutectic composition, its fusing point is 224 degrees centigrade, when making welding flux alloy with SnAgCu, brazing temperature height not only, the highstrung electronic package of heat is caused cause thermal damage easily, thereby make the electronic package degradation, and when lead-free tin spray, copper on electronic package such as the PCB PAD etc. is dissolved in the SnAgCu welding flux alloy easily, cause the copper content in the SnAgCu welding flux alloy to raise, and solder fluidity descends, thereby be difficult to control the planeness of spray tin thickness, and utilize SnAgCu to make welding flux alloy cost height.

Summary of the invention

In view of the above problems, the invention provides a kind of leadless welding alloy that is used for the electronic package welding, when efficiently solving lead-free tin spray, the problem of the easy corrode of Copper Foil of electronic package.

In order to address the above problem, the present invention has adopted following technical scheme: a kind of leadless welding alloy, and wherein, described leadless welding alloy comprises that mainly weight ratio is:

Tin 99%～99.96%;

Copper 0.3%～0.9%;

Nickel 0.01%～0.06%;

Bismuth 0.003%～0.01%.

Preferable, the invention provides a kind of leadless welding alloy, wherein, the optimum weight ratio of described leadless welding alloy is: copper (Cu) 0.9%, nickel (Ni) 0.03%, bismuth (Bi) 0.01%, all the other are tin (Sn).

Preferable, the invention provides a kind of leadless welding alloy, wherein, the optimization weight ratio of described leadless welding alloy is: copper (Cu) 0.5%, nickel (Ni) 0.06%, bismuth (Bi) 0.01%, all the other are tin (Sn).

Preferable, the invention provides a kind of leadless welding alloy, wherein, the optimization weight ratio of described leadless welding alloy is: copper (Cu) 0.8%; Nickel (Ni) 0.06%; Bismuth (Bi) 0.01%, all the other are tin (Sn).

Compared to prior art, the invention provides a kind of leadless welding alloy, not only solved in the lead-free tin spray process, the easy corrode of Copper Foil on the electronic package of printed circuit board (PCB) is in leadless welding alloy, cause copper thickness on the low side, and be difficult to control the problem of spray tin planeness and tin temperature, and effectively reduce cost.

Embodiment

Below in conjunction with embodiment the present invention is made and to further describe.

Embodiment 1:

Various metals are pressed following weight ratio:

Tin 99.06%;

Copper 0.9%;

Nickel 0.03%;

Bismuth 0.01%;

Smelt under certain condition and make the SnCuNiBi leadless welding alloy, this SnCuNiBi leadless welding alloy is applicable in the lead-free tin spray process of printed circuit board surface processing, in order to electronic packages such as PTH plug in component are welded on the welding zone (LAND) or PTH hole of printed circuit board (PCB) and multilayer circuit board.

Wherein, bismuth and copper in tin, have been increased, to improve welding strength, and the nickel that adds can not only resist the copper corrode, in welding process, be used for reducing copper dissolution on the electronic component of printed circuit board (PCB) to the speed of tin, prevent to cause mobile decline because copper content raises in the leadless welding alloy, and be difficult to control the planarization and the tin temperature of spray tin thickness, and can change the crystal phase structure of the intermetallic compound (IMC) that lead-free tin spray surface forms, the crystal phase structure of this improvement can strengthen anti-fatigue life.

Embodiment 2:

Various metals are pressed following weight ratio:

Tin 99.43%;

Copper 0.5%;

Nickel 0.06%;

Bismuth 0.01%;

Wherein, for improving welding strength, bismuth and copper in tin, have been increased, and the nickel that adds is to be used for reducing copper dissolution on the electronic component of printed circuit board (PCB) to the speed of tin in welding process, prevent to cause mobile decline because copper content raises in the leadless welding alloy, and be difficult to control the planarization and the tin temperature of spray tin thickness.

Embodiment 3:

Various metals are pressed following weight ratio:

Tin 99.13%;

Copper 0.8%;

Nickel 0.06%;

Bismuth 0.01%;

Below several welding flux alloys are done antifatigue test, the test of anti-corrode and welding strength test.

1. the antifatigue test is relatively:

To spray SnCu, SnCuNiBi, SnAgCu alloy with lead-free tin spray process with a collection of printed circuit board (PCB) (PCB) surface, and this PCB that is sprayed with different-alloy is placed in 120 ℃ the temperature control box, respectively before putting into, put into thickness and the crystal phase structure of observing the IMC layer in 192 hours, 768 hours, found that SnCuNi has greatly improved than SnCu and SnAgCu alloy on IMC thickens, the IMC of SnCuNi thickens speed and wants slow; And dendrite arm configuration aspects SnCuNi is too than SnCu, and SnAgCu has bigger advantage.

2. anti-corrode test is compared:

The copper wire of getting 4 diameter 300um is placed on respectively among the SnCuNiBi of 235 ℃ of SnPb scolders, 254 ℃ SnCu and SnAgCu and 265 ℃, measures the diameter of this copper wire respectively at the 2nd, 4,6,8 minute, experimental data reference table 1:

Table 1

Found that SnCuNi is behaving oneself best aspect the anti-copper corrode really, verified that the SnCuNi alloy can resist the electronic component copper corrode problem of PCB really.

3. welding strength test:

To with the copper wire of different welding alloy weld diameter 0.6mm on the circular PAD of the PCB of diameter 2mm, do the push-pull effort test then, test result such as following table 2:

Table 2

By the visible SnCuNiBi welding strength of above data maximum.

Claims

1. a leadless welding alloy is characterized in that, described leadless welding alloy comprises that mainly weight ratio is:

Tin 99%～99.96%;

Copper 0.3%～0.9%;

Nickel 0.01%～0.06%;

Bismuth 0.003%～0.01%.

2. leadless welding alloy according to claim 1 is characterized in that, the optimum weight ratio of described leadless welding alloy is:

Tin 99.06%;

Copper 0.9%;

Nickel 0.03%;

Bismuth 0.01%.

3. leadless welding alloy according to claim 1 is characterized in that, the optimization weight ratio of described leadless welding alloy is:

Tin 99.43%;

Copper 0.5%;

Nickel 0.06%;

Bismuth 0.01%.

4. leadless welding alloy according to claim 1 is characterized in that, the optimization weight ratio of described leadless welding alloy is:

Tin 99.13%;

Copper 0.8%;

Nickel 0.06%;

Bismuth 0.01%.