CN107322178A - A kind of new solder for power device package - Google Patents

Abstract

A composite solder used for power device packaging. The invention relates to the composition design of a new composite solder and the preliminary selection and optimization of the new solder. The invention aims to solve the problem of using 80Au-20Sn solder in the current power device package The problem of high cost can replace 80Au-20Sn at a relatively low temperature. The cost of the new solder is more than 99.9% lower than that of 80Au-20Sn. Its main feature is that it has better high temperature resistance than the commonly used SAC305. % of Ag, 0.10% to 2.00% of Cu, 0.10% to 0.50% of Ni, 2.00% to 5.00% of Sb and the rest of Sn. The present invention uses Sn-Sb alloy as the matrix, and by adding alloy elements (Cu , Ag, Ni), the brazing filler metal is prepared by smelting, the melting point of the brazing filler metal is 237 ° C ~ 244 ° C, and the weldability and mechanical properties are good. The composite solder filler metal prepared by the invention can be used for gold-plated and nickel-plated copper plates on the surface. Welding between.

Description

A new type of solder for power device packaging

technical field

The invention relates to the composition design of several novel composite solders.

Background technique

The development of traditional semiconductor materials represented by Si and GaAs has promoted the rapid development of optoelectronics and microelectronics. However, due to the limitations of material properties, the first and second generation semiconductor materials are not enough to meet the requirements of modern electronic technology development for high temperature and high temperature. However, the third-generation semiconductors represented by SiC and GaN have large band gap, high breakdown voltage, high thermal conductivity, high electron saturation drift rate and radiation resistance. Strong ability and other performances make it popular in optoelectronic devices, high-frequency high-power, high-temperature electronic devices, etc.

80Au-20Sn solder is a high-temperature solder that was studied earlier. The 80Au-20Sn alloy is a binary eutectic composition with a eutectic point of 280°C. The brazing temperature is relatively moderate, which meets the melting temperature requirements of high-temperature solder. The Au-based alloy has high strength, excellent electrical and thermal conductivity, and strong corrosion resistance. It does not require flux during welding to ensure the cleanliness of the chip. However, Au-based alloys are hard, have high tensile strength, low elongation, and poor machinability, making it difficult to process them into wires or strips. Moreover, when the interconnection joint is in service at a higher temperature, due to its high hardness, it is difficult for the joint to undergo plastic deformation, and the thermal stress generated by the joint is easily transmitted directly to electronic components such as chips, which may lead to failure of components such as chips in severe cases. The most important thing is that the cost of Au-based alloys is too high, so the applicable occasions are extremely limited. The patent titled "Tin-antimony-silver-nickel alloy foil-shaped solder and its preparation method (patent application number: CN201010623783.0, application date: 2010.12.31)" proposes a hermetic sealant for integrated circuits Packaging solder, its composition and mass percentage are: antimony, 8-11%, silver, 3-20%; the name is "high temperature lead-free solder alloy (patent application number: CN201280007265.3, application date: 2012.08.08)" The patent proposes a high-temperature lead-free packaging solder, whose composition and mass percentage are: antimony, 35-40%, silver, 13-18%, Cu, 6-8%, tin, and the balance. The melting point of the solder is as high as 299-337°C, and the solid phase rate of the solder is 100% at 280°C. However, the solder with high brittleness has limited application occasions. The patent titled "A SnAgCuNi-based lead-free solder alloy (Chinese patent number: CN200710041687.3, application date: 2007.6.6)" proposes a SnAgCuNi-based lead-free solder alloy, whose composition and mass percentage are: 1.5- 2.5% Ag, 0.1-0.8% Cu, 0.01-0.5% Ni, 0.001-0.1% P, 0-0.01% Bi, the melting point of this solder is about 220°C, which cannot meet the third-generation semiconductor power requirements. The temperature requirements of the device package.

The development of new solders and other interconnection processes that replace or partially replace Au-based solders has become an urgent need in the industry and has important practical significance. Sn-Sb alloys have a narrow melting range (232-243°C) for Sn-Sb (Sb≦10%) alloys, good compatibility with existing solders, excellent mechanical properties, and much lower cost than Au-Sn alloys. Therefore, it has attracted much attention as a high-temperature lead-free candidate material. In order to further improve the performance of the solder, the Sn-Sb alloy is modified by adding other metal elements, so that the solder joints have higher reliability during service.

Contents of the invention

The purpose of the present invention is to solve the problems of poor processability and high cost of connecting high-temperature solders for existing power devices, and provide a new type of solder that can replace the existing Au-based alloy solders at relatively low temperatures. The cost of new solder is only about half of the cost of SAC305 solder, and less than 0.1% of the cost of Au80Sn20 solder.

The new type of solder is based on Sn-Sb alloy and made by adding alloy elements. The experiment adopts the form of Sn-Sb, SnCu, Sn-Ag, Sn-Ni master alloy for smelting. The high-temperature solder of the present invention is composed of the following components according to the mass percentage: the Sb content is 2-5%, and the Cu content is 0.1-2%. , Ni content is 0.1-0.5%, Ag content is 0.1-0.5%, and the rest is Sn.

The brazing filler metal of the present invention is formed by heating and smelting raw materials in a quartz tube under an argon protective atmosphere through a high-frequency induction heater, and the smelted block alloy can be cut into sheet brazing filler metal or powder material or solder paste.

The present invention is achieved by the following technical solutions: a lead-free solder for power device welding, the composition percentage of the solder is: Sb content is 2-5%; Cu content is 0.1-2%; Ni content is 0.1% ~0.5%; the balance is tin (Sn). The above scheme optimizes the components of Cu, Ag and Ni, and obtains a high-temperature solder with good wettability and high shear strength.

The mechanism of the invention is: adding Ag and Cu can significantly improve the wettability of solder, improve thermal conductivity and electrical conductivity. Adding Sb can increase the melting point of the solder. Adding Ni refines the microstructure of solder joints and improves the comprehensive mechanical properties of solder joints.

The present invention can adopt the smelting method of conventional production solder to obtain, and the method that the present invention preferably adopts is: according to the order of Sn ingot and Sn-Sb alloy, Sn-Cu and Sn-Ag, Sn-Ni alloy according to the composition distribution ratio of design Add in sequence, melt in a protective atmosphere of high-purity argon, and pour it on an aluminum mold to cool after melting.

The invention has the advantages of low solder cost, high strength and excellent weldability.

Description of drawings

Figure 1: Basic properties of different examples (1, 2, 3, 4) in Table 1.

Fig. 2: Line-scan EDX analysis of IMC of solder joint interface IMC of specific example 1 solder Sn-3Sb-0.5Cu-0.1Ni-0.1Ag/Cu.

Fig. 3: is the spreading rate of different examples (1, 2, 3, 4) in table 1.

Fig. 4: is the shear strength of different examples (1, 2, 3, 4) in table 1.

The present invention will be further elaborated below through 4 embodiments in conjunction with accompanying drawings 1-4.

The materials used in the following 4 examples are Sn ingots, Sn-Cu master alloys, and Sn-Ag master alloys. The method is to follow the Sn ingots and Sn-Sb alloys, Sn-Cu and Sn- Ag and Sn-Ni alloys are added sequentially, smelted in a protective atmosphere of high-purity argon, and poured on an aluminum mold to cool after smelting. The required solder wire can be obtained by extrusion and drawing, and the new solder can also be prepared into solder paste for use.

Example 1

The composition and weight percentage of the lead-free solder used for power device welding are: Sb3%, Cu0.5%, Ni0.1%, Ag0.1%, and the balance is Sn.

Solder performance testing: the solidus temperature is 229.67°C, the liquidus temperature is 240.55°C (taking into account the experimental error), the spreading rate is 66.618%, and the shear strength is 72.2Mpa.

Example 2

The composition and weight percentage of the lead-free solder used for power device welding are: Sb3%, Cu1%, Ni0.3%, Ag0.3%, and the balance is Sn.

Solder performance testing: the solidus temperature is 220.03°C, the liquidus temperature is 238.48°C (test error is considered), the spreading rate is 67.652%, and the shear strength is 74.07Mpa.

Example 3

The composition and weight percentage of the lead-free solder used for power device welding are: Sb3%, Cu2%, Ni0.5%, Ag0.5%, and the balance is Sn.

Solder performance testing: the solidus temperature is 220.62°C, the liquidus temperature is 237.51°C (taking into account the experimental error), the spreading rate is 68.750%, and the shear strength is 75.349Mpa.

Example 4

The composition and weight percentage of the lead-free solder used for power device welding are: Sb5%, Cu1%, Ni0.1%, Ag0.5%, and the balance is Sn.

Solder performance testing: the solidus temperature is 222.27°C, the liquidus temperature is 240.55°C (taking into account the experimental error), the spreading rate is 69.185%, and the shear strength is 77.34Mpa.

The brazing material obtained in this embodiment adopts power compensation differential scanning calorimetry, and uses the American PerkinElmer～Pyris Diamond DSC power compensation differential scanning calorimeter to measure the melting temperature of the solder alloy, and the quality of the solder is 5-10mg , In this test process, the heating rate is 10°C/min, and the temperature range is 180-300°C. During the test, high-purity nitrogen gas is used to protect the sample.

Wettability was tested using the GB/T11364-2008 standard. The standard sample is a single-sided copper-clad laminate test piece of 40×40×1 mm, and the mass of the solder sample is 0.25g. The heating equipment is an R340C eight-zone lead-free reflow oven with a peak temperature of 280°C, and their wettability is evaluated by their spreading rate on the Cu substrate.

Adopt Japan PTR-1101 bonding strength testing machine to test the shear strength of the micro-solder joint prepared with the solder of this embodiment, the shear speed is 0.5mm/s, the shear distance is 1mm, the positioning distance is 175μm, and the size of the ball is 700µm. The basic properties of the brazing material in each embodiment are shown in Figure 1.

Claims (3)

1. a kind of high-temp solder for power device package, it is characterised in that solder is by five kinds of composition Sn, Sb, Cu, Ag, Ni groups Into wherein Sb contents are that 2~5%, Cu contents are that 0.1~2%, Ni contents are that 0.1~0.5%, Ag contents are 0.1~0.5% surplus For tin（Sn）.

2. the new type high temperature solder described in claim 1, it is characterised in that using Sn-Sb alloys as matrix, by adding alloy member Element is made, and experiment carries out melting in the form of intermediate alloy, devises orthogonal test and component content has been carried out preferably, this hair Bright solder is that raw material is formed in quartz ampoule under the protective atmosphere of argon gas through the heating melting of high-frequency induction heating instrument, is smelted into Block alloy can be cut into sheet solder with warp, and powder or soldering paste can also be made.

It is the addition alloy in the form of intermediate alloy 3. being used for the high-temp solder of power device package as claimed in claim 2 Element, wherein Sb：Sn-30Sb、Cu： Sn-10Cu、 Ag：Sn-20Ag、Ni： Sn-1Ni.