CN100431747C

CN100431747C - Preparation method of leadless soldering ball

Info

Publication number: CN100431747C
Application number: CNB2005100867281A
Authority: CN
Inventors: 徐振武
Original assignee: Individual
Current assignee: Langfang Bondtron Electronic Material Co ltd
Priority date: 2005-10-27
Filing date: 2005-10-27
Publication date: 2008-11-12
Anticipated expiration: 2025-10-27
Also published as: CN1954946A

Abstract

A method for preparing the Pb-free soldering tin balls includes such steps as providing raw materials, adding antioxidant consisting of P and T1 and grains fining agent, smelting to become liquid state, immersing the most of a spherical mould with semi-spherical pits on its surface in said molten soldering tin, making said spherical mould to rotate for filling the molten soldering tin in said semi-spherical pits, cooling in N2, for solidifying the molten soldering tin in said pits, and releasing the soldering tin balls.

Description

A kind of preparation method of Pb-free solder ball

Technical field

The present invention relates to a kind of preparation method of solder ball, relate in particular to a kind of Pb-free solder ball preparation method who is exclusively used in the integrated circuit encapsulation.

Background technology

Prepare general wired smelting process, spray shaping technology and the swing-shaping technology etc. of cutting of technological process that adopt of solder ball at present.Line is cut smelting process and is adopted method hot candied, that cut off, causes a tolerance easily and cut off tolerance to produce deviation, and yield rate has only about 10%; Spray shaping technology is to bring the fluid moulding into by gas, without any rule, causes size uneven, and yield rate can only reach 5%, and prolongs the production time, and power consumption is big, has caused the raising of production cost.The pendulum moulding process is that its drop is wayward by metal melting liquid swing discharging, thereby preparation solder ball particle is inhomogeneous.To be that technology is carried out in the process operation many for the common shortcoming of these technologies in addition, this has taken more usage space virtually, and the Pb-free solder ball quality requirement is very superior, very harsh to environmental requirement, must under the high purification condition, produce, operation is many more, and the probability that causes substandard product to occur is just big more, and the cost of product also will increase simultaneously.

Aspect density control, the external at present chemical method process method of smelting that adopts is realized grain refinement, and this method is difficult to guarantee that the density of product is even in actual mechanical process through practice test, density is grasped bad, is difficult to guarantee the dimensional accuracy of product (as soldered ball).

Aspect smelting temperature, the heating of external at present employing stove silk, though the heating of stove silk can reach the necessary temperature of melting, but because the proportion difference of various metals, certain tenor height of output product that when forming output product such as solder ball, inevitably can cause, certain tenor is low, causes output product density unevenness, thereby influences welding quality.

Summary of the invention

The object of the present invention is to provide a kind of Pb-free solder ball preparation method.

For achieving the above object, preparation method provided by the invention, its key step is:

A) in the Pb-free solder material component, add antioxidant and grain refiner, be smelted into liquid; Described antioxidant is that weight ratio is 1: 1 phosphorus and a thallium, and its addition is the 0.006-0.03% of raw material weight, preferably is 0.01%: described grain refiner addition is the 0.003-0.005% of scolding tin weight, preferably is 0.005%;

B) surface is provided with some spherical moulds that are the semicircle shape round pool; its scolding tin melt liquid that places over half at least; rotate this mould; make the little round pool of die surface fill with the scolding tin melt liquid; when treating that spherical mould rotates to the nitrogen mouth; cooled and solidified typing under nitrogen protection, by the continuation rotation of mould, the solder ball of typing falls from discharging opening.

Described its component of Pb-free solder raw material and weight ratio are Sn 95.5%, and Ag 4%, and Cu 0.5%.

The round pool diameter of described spherical die surface and the degree of depth are decided by the solder ball size of needs preparation.

Described discharging opening is provided with extractor fan.

In sum, owing to technology and the mould that the present invention adopts, guaranteed the uniformity of scolding tin particle and density.

Description of drawings

Fig. 1 is a schematic flow sheet of the present invention.

Fig. 2 is melting container of the present invention and mould schematic diagram.

The specific embodiment

Below in conjunction with accompanying drawing the present invention is described in detail.

Please, be the schematic flow sheet of preparation process of the present invention in conjunction with Fig. 1.Its concrete operations step is as follows:

Prepare the raw material of Pb-free solder according to the weight of Sn 95.5%-Ag 4%-Cu 0.5%, be understandable that this proportioning just for example, press 0.01% of raw material weight again and add antioxidant, add 0.005% grain refiner of raw material weight simultaneously again, became liquid in 30 minutes in 450 ℃ of meltings; The antioxidant that the present invention adopts is that 1: 1 phosphorus and thallium formed by weight ratio: grain refiner is known commodity, and available from Jinan electroplate liquid factory, and this melt liquid makes it protect liquid condition in 240 ℃ of insulations down.

Please in conjunction with Fig. 2.The container A that the present invention carries out melting is equipped with a rotatable spherical mould 1, and this mould 1 surface is provided with some roundlet holes 2 that are semicircle shape, and according to this example, the diameter of this round pool 2 and the degree of depth are about 5000 solder ball of per kilogram feedstock production.(shown in arrow among Fig. 2) this mould 1 will also be rotated in this mould 1 immersion scolding tin over half at least melt liquid 3.When the round pool on the die surface 2 rotates to when horizontal, be full of the scolding tin melt liquid in the little round pool of tool, and in the cooled and solidified typing under nitrogen 4 protections of this position, the solder ball particle size behind mould shape can guarantee its basically identical.By the continuation rotation of mould 1, the solder ball 5 of typing falls into ball sieve 7 from discharging opening 6 and screens, and branch detects defective part and carries out quality control with further assurance product quality, last inflated with nitrogen packing.

Because solder ball 5 its volumes after the moulding are less, weight is lighter, for accelerating its falling speed, is provided with extractor fan (this extractor fan is known technology, and is not shown in the figures) at discharging opening 6.

Rotation about spherical mould can be a known technology about being rotated by the motor drives mould, so the present invention seldom be described by a motor drives.

Its material of spherical mould of the present invention does not have strict the qualification, as long as ability is lived the temperature of raw materials melt state.

Need to prove, the present invention for embodiment in the component of raw material, auxiliary material and other operating condition etc. have been provided more concrete numerical value, its purpose only is not mean that for the ease of it will be appreciated by those skilled in the art that method of the present invention can only prepare the solder ball of above-mentioned numerical value representative.Similarly, the present invention changes in the container that spherical mould and heat-preserving equipment are installed after also can earlier the scolding tin raw material being melt into liquid again, though this is not the emphasis that the present invention discusses, the method that forms solder ball should belong to the inventive method category.

Claims

1. the preparation method of a Pb-free solder ball, its step is as follows:

A) in the Pb-free solder material component, add antioxidant and grain refiner, be smelted into liquid;

Described antioxidant is that weight ratio is 1: 1 phosphorus and a thallium, and its addition is the 0.006-0.03% of Pb-free solder raw material weight;

Described grain refiner addition is the 0.003-0.005% of Pb-free solder raw material weight;

2. according to the preparation method of claim 1, it is characterized in that the component of described Pb-free solder raw material and weight ratio are Sn 95.5%, Ag 4%, and Cu 0.5%.

3. according to the preparation method of claim 1, it is characterized in that the addition of described antioxidant is 0.01% of a Pb-free solder raw material weight.

4. according to the preparation method of claim 1, it is characterized in that the addition of described grain refiner is 0.005% of a Pb-free solder raw material weight.

5. according to the described preparation method of claim 1, it is characterized in that the round pool diameter of described spherical die surface and the degree of depth are decided by the solder ball size of needs preparation.

6. according to the described preparation method of claim 1, it is characterized in that described discharging opening is provided with extractor fan.