PCB Solderability Test Standard
As pretty important process of PCB manufacturing, PCB soldering and the solderability test are very useful to affect the performance and quality of the finished products. Solderability measures how well metal is wetted by molten solder to secure those connections. It’s one of the most essential PCB testing methods.
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Evaluating solderability will tell your PCB tester whether or not the attached components, like leads and terminations, can withstand the scorching temperatures that come with soldering. In this passage, we will focus on PCB solderability test, if you are interested in it, please check and read the content to learn more information.
Why is PCB solderability test important?
Solderability testing helps determine if a component provides the degree of wetting necessary for a solid solder connection. A poor test result indicates a less-than-optimal connection. Without this testing, you may have to rework the connections.
Solderability testing is effective during different aspects of production, such as when:
· Evaluating PCB coating, solder, and flux
· Benchmarking
· Performing quality control
This test is necessary for PCB projects because solderability can degrade over time for components left in storage, typically due to contamination.
What are the main types of PCB solderability tests?
There are numerous types of solderability tests, but the most typical methods are:
Dip and Look Method
Engineers widely apply the dip and look method in-process QA and reliability checking. In other words, the dip and look method is a qualitative test procedure. Basically, you use the physical characteristics of a component to determine its solderability.
You can apply the dip and look method in leaded and leadless terminations. It comprises three major steps: pre-conditioning, the use of flux, and terminations soaking. You should carry out the dip and look solderability test by exposing the parts to steam conditioning for a maximum of eight hours. After steaming, you should dip the terminals into the solder.
Wetting Balance Analysis
The wetting balance analysis method is a quantitative process you conduct on surface-based packages, such as BGA and CGA. The technique assesses the wetting powers of the liquefied solder on the assessment surface.
First, you should insert the connections in a non-activated flux. Secondly, load the package into the wetting balance arm before dipping the contacts in liquid solder. Then, plot the force applied on the balance arm as a time factor. Remember, the plot begins with a negative wetting force (the non-wet state).
The solder density and surface tension determine the wetting time, a crucial aspect you can use to measure solderability. Remember that most engineers use the wetting balance analysis method as an engineering instrument and not a manufacturing monitor.
Surface Mount Simulation Test
You can use the surface mount simulation test for any Surface Mount Technology (SMT) part. This includes components where you cannot use other testing methods, such as the wetting balance analysis.
You can carry out surface mount simulation by screen printing a solder paste into a ceramic container. After that, you should place the part into the paste. Lastly, you should put it into a convection reflow plate. Remember that you can use the surface mount simulation test on any surface-based parts, like BGA and CGA.
What are the standard methods of PCB solderability tests?
The test temperature is the temperature before the solder is in contact with the metal being soldered, so it is usually the same temperature as in the solder bath. The actual temperature of the wetted surface is, in almost all cases, lower than the temperature of the solder bath, and the actual temperature of the wetted surface is not constant and there is a significant change.
Wetting balance method
Wetting Balance Test is a solderability test method for identification that can quantitatively study the solderability of samples of any shape. Under normal circumstances, the solder terminals or pins of the components are tested, but can also be used for other aspects such as PCB, thick film substrate, solder, etc.
Dip method
Dip Test, also known as dip soldering, is an inexpensive, fast, and qualitative solderability test method, but the test results are often subjective. Wetting balance methods can give quantitative results, but they are slower and more expensive. The dipping method is very simple, that is, the test sample (PCB or component lead or solder end) is immersed in a molten solder pot, and the degree of wetting – the percentage of the wetted area and the degree of non-wetting are visually observed. It can be used for testing the solderability of solder joints on PCBs and components.
Spreading method
The spreading method is also called the flow parameter method and the area expansion method. The spreading method is used to test both the activity of the liquid flux and the activity of the solder paste flux. Quantitative solder is placed on the copper surface of the controlled oxide thickness. After applying a certain amount of flux, the solder is hot melted. If the oxide layer is not removed, wetting will not occur. The stronger the flux activity, the more oxide removed, the lower the solder stack height.
Aging
Before performing the reliability test, the PCB manufacturer needs to aging the test sample because the just-produced element PCB quote, the solderability of the soldered surface is generally not problematic, but after storage for a while, It will be degraded by oxidation. The test must consider the effect of normal storage conditions on solderability. In the electronics manufacturing industry, components and PCBs often require a certain shelf life of storage, usually 6-12 months. Therefore, It is obviously impractical to wait for this period and then perform measurements, so it is necessary to adopt an accelerated storage aging method.
PCB Knowledge ⋅ 09/01/2021 09:04
