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Method for rapidly evaluating growth tendency of Sn crystal whiskers of Sn-based solder

A solder and whisker technology, applied in the field of rapid evaluation of Sn whisker growth tendency of Sn-based solder

Inactive Publication Date: 2016-11-16
HARBIN INST OF TECH SHENZHEN GRADUATE SCHOOL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Due to the occasional and long-term nature of whisker growth, there is still no fast and feasible method to evaluate the whisker growth tendency of various Sn-based solders.

Method used

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  • Method for rapidly evaluating growth tendency of Sn crystal whiskers of Sn-based solder
  • Method for rapidly evaluating growth tendency of Sn crystal whiskers of Sn-based solder
  • Method for rapidly evaluating growth tendency of Sn crystal whiskers of Sn-based solder

Examples

Experimental program
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Effect test

Embodiment 1

[0027] Such as figure 1 with 2 As shown, a 3mm thick pure Mg plate is selected, the pure Sn solder is pressed into a solder sheet with a thickness of 300μm, the weld width is 200μm, and the Mg / Sn / Mg sandwich structure is heated to 240°C by induction, and the operating frequency is 20KHz , an ultrasonic wave with an amplitude of 8 μm was applied for 15 s. After the sample is polished and placed in a room temperature environment (temperature 20-25°C, relative humidity 30-45% RH), Sn whiskers appear 2-4 hours after polishing, and then grow rapidly.

Embodiment 2

[0029] Such as figure 1 with 3 As shown, a 2mm thick pure Mg plate is selected, and the Sn-0.7Cu solder is pressed into a solder sheet with a thickness of 400μm, and the weld width is 300μm. The Mg / Sn / Mg sandwich structure is heated to 240°C by induction, and the frequency of use is Ultrasound at 20KHz with an amplitude of 5μm acts for 12s. After the sample is polished and placed in a room temperature environment (temperature 20-25°C, relative humidity 30-45% RH), Sn whiskers appear 2-4 hours after polishing, and then grow rapidly.

Embodiment 3

[0031] Such as figure 1 with 4 As shown, a 5mm thick pure Mg plate is selected, and the Sn-3Ag-0.5Cu solder is pressed into a solder sheet with a thickness of 200 μm, and the weld width is 150 μm. The Mg / Sn / Mg sandwich structure is heated to 230 ° C by induction. Ultrasonic waves with a frequency of 25KHz and an amplitude of 10μm were used for 6s. After the sample is polished and placed in a room temperature environment (temperature 20-25°C, relative humidity 30-45% RH), Sn whiskers appear 2-4 hours after polishing, and then grow rapidly.

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Abstract

The invention provides a method for quickly evaluating the growth tendency of Sn whiskers of Sn-based solder, which provides a carrier for the growth of whiskers by preparing Mg / Sn-based solder / Mg ultrasonically assisted brazing joints. In the process of ultrasonic brazing, due to the action of ultrasonic waves, a large number of Mg atoms enter the liquid solder, and most of the Mg atoms combine with Sn atoms to generate Mg at the interface and inside the solder. 2 Sn; another part of Mg atoms exists in the solder in the form of solid solution. After the solder is solidified, the solid-dissolved Mg atoms are in a thermodynamically unstable state, and Mg atoms react with Sn atoms to form new Mg atoms. 2 Sn, and produce volume expansion, which in turn creates stress in the weld. Sn whiskers grow rapidly under stress. The invention can compare the Sn whisker growth tendencies of different solders by statistically comparing the whisker growth conditions on the surface of welds prepared by different Sn-based solders, and provide important solder reliability parameters for the electronic industry.

Description

technical field [0001] The invention belongs to the technical field of materials, in particular to a method for rapidly evaluating the growth tendency of Sn whiskers of Sn-based solder. Background technique: [0002] The problem of metal whiskers has been widely concerned by the scientific community since the end of World War II. At that time, Cd was commonly used as a surface coating material for electronic components. In 1946, Cobb first observed cadmium whiskers sufficient to cause short circuits. Whiskers, especially Sn whiskers, are still of concern today. [0003] Although there is still no complete consensus on the mechanism of whisker growth, the current general view is that internal compressive stress is one of the main driving forces for whisker growth. The compressive stress required for whisker growth comes from the following aspects: 1. The residual stress generated during the coating preparation process; 2. The stress generated by the mechanical action proces...

Claims

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Application Information

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IPC IPC(8): G01N33/00G01N1/28G01N1/32
CPCG01N33/20G01N1/28G01N1/32
Inventor 杨海峰李明雨张志昊
Owner HARBIN INST OF TECH SHENZHEN GRADUATE SCHOOL
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