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A method for measuring the ratio of white tin to gray tin in tin and tin alloy samples

A tin alloy and sample technology, applied in the field of low temperature reliability research of solder, can solve the problems of slow transformation and low sensitivity

Active Publication Date: 2020-11-10
HARBIN INST OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to solve the problem of low sensitivity of the existing Sn low-temperature phase change detection method, and provide a method for measuring the ratio of white tin to gray tin in tin and tin alloy samples. This method is simple to operate and can significantly detect early Sn phase transformation, the transformation from β-Sn to α-Sn is quite slow, and Sn needs to nucleate and grow during the process, and the incubation period takes months or even years to complete, but based on the different physical and chemical properties of white tin and gray tin, especially It is a 27% volume change, which can accurately detect the occurrence of tin plague and the gray tin transformation ratio in the sample, which is not only beneficial to the study of Sn low-temperature phase transition, but also plays an important role in scientific research and actual workpiece safety testing

Method used

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  • A method for measuring the ratio of white tin to gray tin in tin and tin alloy samples
  • A method for measuring the ratio of white tin to gray tin in tin and tin alloy samples
  • A method for measuring the ratio of white tin to gray tin in tin and tin alloy samples

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specific Embodiment approach 1

[0024] Specific implementation mode 1: This implementation mode records a method for determining the ratio of white tin to gray tin in tin and tin alloy samples. Method variable is the relation of temperature, time and volume, it is characterized in that: described method specific steps are as follows:

[0025] Step 1: Prepare a cube tin or tin alloy sample with a side length of 1 cm;

[0026] Step 2: Measure the volume of the sample in tap water at a constant temperature of 10°C, such as figure 1 shown;

[0027] Step 3: Put the sample into the high and low temperature test box, and place it in the high and low temperature test box for 10 minutes; the model of the high and low temperature test box is TGDW-500TA;

[0028] Step 4: Take out the sample, and when the temperature rises to 9°C, put it into the tap water at a constant temperature of 10°C as described in Step 2 to measure its volume;

[0029] Step 5: put it into the high and low temperature test chamber again, reduc...

specific Embodiment approach 2

[0033] Specific embodiment two: a method for measuring the ratio of white tin in tin and tin alloy samples into gray tin as described in specific embodiment one, in step three, the low temperature treatment is timing cooling or constant temperature change, (1 ) Timely cooling is to place the sample in a low temperature environment of -20 ° C ~ - 120 ° C for 10 minutes, and then change the temperature of the storage environment, the cooling gradient is 20 ° C; (2) Constant temperature change is to place the sample at -40 ° C The low temperature environment, and then change the length of storage time, each increase of 10 minutes.

[0034] In step 5 and step 6, reduce the temperature of "phase change low temperature environment" by a step, such as -10°C to -30°C, until -120°C; keep the temperature of "phase change low temperature environment" unchanged, and increase the processing time each time. Measure for 10 minutes until the required time such as 200 hours. In step 8, when t...

Embodiment 1

[0041] This embodiment takes pure Sn as an example to describe in detail (other solder alloys are similar):

[0042] Step 1: Prepare a regular Sn sample with a side length of 1 cm;

[0043] Step 2: measuring the volume of the Sn sample in a liquid medium at a constant temperature of 10°C;

[0044] Step 3: Put the Sn sample into the "phase change low temperature environment" at -20°C for 10 minutes;

[0045] Step 4: Take out the sample, put it into the above-mentioned liquid medium with a constant temperature of 10°C to measure its volume when the temperature rises to 9°C;

[0046] Step 5: Lower the temperature of the "phase change low-temperature environment" by 10°C each time, and the processing time is still 10 minutes;

[0047] Step 6: Repeat steps 3-5 above until the temperature reaches -120°C;

[0048] Step 7: Draw different "phase change low temperature environment" temperatures and corresponding sample volume curves;

[0049] Step 8: According to the inflection poin...

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Abstract

The invention discloses a method for determining the proportion of white tin converted to grey in a tin and tin alloy sample and belongs to the technical field of research on low-temperature reliability of brazing filler metal. The method comprises the steps as follows: the sample is placed in a constant-temperature liquid medium for measurement of the initial volume, the sample is placed in a low-temperature phase change environment, the environmental temperature or placement time is changed, the sample is taken out and heated to the initial temperature, the sample is placed back to the constant-temperature liquid medium again, the volume of the sample at different temperatures or after different placement time is measured, a volume change curve is drawn, and the Sn low-temperature phasechange process such as the conversion start point and conversion proportion is monitored according to the change curve. The method has the advantages as follows: occurrence of tin pest and the proportion of converted grey tin in the sample can be effectively detected by use of the density change of grey tin and white tin in the Sn phase change process, and different from existing phase change detection methods, the method has higher sensitivity.

Description

technical field [0001] The invention belongs to the technical field of low-temperature reliability research of solder, and in particular relates to a method for measuring the ratio of white tin to gray tin in tin and tin alloy samples. Background technique [0002] In recent years, as the use of lead has been banned in the electronic industry, people have been researching lead-free solders that can replace Sn-Pb solders. Prior to this, the widespread use of Sn-Pb solder did not see the occurrence of gray tin problems, and due to the relatively small amount of alloying elements contained in the widely used Sn-based lead-free solder, its Sn content can reach 95% ~99% or more, its composition is closer to pure tin, the problem of tin plague has gradually been paid attention to, and some new data can prove that under long-term low temperature conditions, the risk of gray tin formation in lead-free solder will be greater, Therefore, the problem of tin plague has always been a se...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N25/02
CPCG01N25/02
Inventor 王春青赵厢汐籍晓亮安琪
Owner HARBIN INST OF TECH