Solderability test equipment – types of testing and its importance
Speaking of Solderability testing, you can perform both quantitative and qualitative analysis. One of the most common forms of Solderability testing is the “dip and look” test. It has been there for more than 50 years. In this process, you take the sample in the Solderability test equipment and dip it into molten solder and then withdraw it in a controlled manner. Once the melted bar is removed, the sample is inspected for a certain percentage of the solder coverage. If the solder coverage is more than 95%, then it is considered acceptable. The whole process is a qualitative analysis of Solderability.
As we mentioned above, you can also perform quantitative analysis. The most common form of quantitative analysis is the wetting balance test. This test involves a controlled immersion of the sample within a molten solder bath while measuring the forces encountered by the sample. Initially, the sample will encounter some resistance once it comes in contact with the molten solder. But as the solder begins to wet the sample, the initial resistance will be replaced by the wetting forces “pulling” on the sample. It is displayed on time versus the force plot. The result is such that a stronger and quicker pulling is required. It indicates that the sample has good Solderability.
Tinning is another method of Solderability testing. Here the Solderability test equipment is used for replacing the existing surface finish with a pristine solder finish of the desired alloy. The tin that is used in the tin-lead and lead-free solder alloys is aggressive, considering the capability to dissolve any other metals. Whenever a sample is dipped within the molten solder bath, the tin within the tub will disappear and then remove the surface finish. Also, it will dissolve some of the basis metal as well. The amount of basis metal to be removed will be a function of the duration of immersion, whether the solder bath is static or dynamic. It will also depend on the temperature of the tub as well.
Once the sample is removed from the solder bath, it will have a fresh coating of the solder alloy instead of the original surface finish. Removing the basis metal is a primary concern while using the lead-free alloys because the higher tin percentages are much more aggressive than tin-lead alloys. Now, when should you use the Solderability test equipment? The Solderability testing is an excellent tool for determining whether the surface finish of the selected components will offer the degree of wetting required for the acceptable solder connections.
Like, if the Solderability testing results are indicating anything less than optimal Solderability. If the optimal value is not reached, it will result in poor wetting and defective solder connections that require rework and additional processing. The Solderability testing also is done for determining the effects of the storage conditions present on the surface finish. If the accelerated aging is added, the examination will also estimate the acceptable storage life. Testing is also used for verification of the components received from the vendor.