What are the solderability inspection methods for components?

Date：2022-06-23 18:01:31Views：980

The solderability test of components is mainly aimed at the solderability of welding ends or pins. The primary cause of solderability problems is oxidation or pollution on the surface of components' welding ends or pins, which is also the primary factor affecting the reliability of SMA welding. Oxidation or pollution is easy to occur on the welding end or pin surface of components. In order to ensure the welding reliability, it is necessary to pay attention to the packaging conditions and environmental conditions of components during transportation and storage. It is also necessary to take measures to prevent components from being exposed to the air for a long time before welding, and to prevent them from being stored for a long time. Before welding, it is necessary to pay attention to the solderability test of components to facilitate the timely detection and treatment of problems. There are many ways to test the solderability of components. The following is a brief introduction to several commonly used test methods.

Solderability test method for components

1. welding groove moistening method

The welding groove moistening method is one of the most original component solderability test methods. It is a test method evaluated by visual inspection (or through a magnifying glass). Its basic test procedure is: immerse the sample in the flux and take it out, remove the remaining flux and then immerse it in the molten solder groove about twice the actual production welding time, and then take it out for visual evaluation.

This test method is usually carried out with an immersion tester, which can control the immersion depth, speed and residence time of the sample according to the regular parameters, and get the test results more conveniently and quickly. This test method can only get a qualitative conclusion of visual measurement. It is not suitable for the test occasions with quantitative accuracy requirements, but it is more suitable for the quick and intuitive test requirements of SMT assembly production site, and it is still commonly used. The qualification criteria for solderability test by welding groove moistening method is: all samples to be tested shall show a continuous solder coverage, or at least 95% of the solder coverage of each sample shall be qualified.

2. welding ball method

The solderability test of the solder ball method is also a simple qualitative test method. Its basic principle is: select the solder balls with appropriate specifications according to relevant standards and heat them on the heating head to a regular temperature; Place the parts (leads or pins) to be tested of the sample coated with flux horizontally, and immerse them into the solder ball at a regular speed. Record the time when the leads are completely wet and completely wrapped by the solder ball. Measure the weldability by the length of this time. The evaluation criteria for solderability test by using the solder ball method are as follows: the time when the lead is completely wet by the solder ball is about 1s, and it is unqualified if it exceeds 2S.

3. wet weighing method

The basic principle of the device and test principle for solderability test by wet weighing method is as follows: hang the component sample to be tested on the scale pole of the flexible scale; Immerse the part of the sample to be tested into the melting weld at a constant temperature to a regular depth; Together with this, the resultant force of buoyancy and surface tension on the immersed sample in the straight direction is measured by the sensor and converted into a signal, and recorded into a force time function curve by a high-speed characteristic curve recorder; The function curve is compared with the ideal moisture weighing curve obtained from an experimental sample with the same properties and dimensions and which can be completely wet, so as to obtain the test results.

Moisture balance tester is an instrument for weldability test by using moisture weighing method. When the test sample is soaked with molten solder at a predetermined depth, at first the solder level is pressed down into a meniscus shape, because the cohesion of the solder is greater than the adhesion between the molten solder and the test sample (PIN), making the wet angle 8 greater than 90. The straight weight FR and buoyancy FB of the surface tension fr of the meniscus under the solder are in the same direction, and the test samples are evaluated upward. When the sample reaches the welding temperature, the adhesion between the sample and the molten solder is greater than the cohesion of the solder, and the molten solder begins to wet the sample, so that the meniscus gradually bends upward until 6 equals 90 °. The test sample is only subject to the effect of buoyancy. Then, the molten solder is continuously wet, and the sample presents an upward meniscus, 9 ° is less than 90 °, and a downward tension effect occurs until the vertical weight fr of the surface tension FR is equal to the buoyancy FB, reaching the moisture balance.

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