Solderability Test: Understanding PCB Solderability Testing

You need a solder testing to minimize component solderability issues in PCB manufacturing. You can use preventive measures, such as the wetting balance solder method, to remove poorly soldered circuit board parts. All electronic products and PCBs that pass the test will definitely solder well in volume production.

Basically, solderability testing will enable you to project your soldering process’ success rate before carrying out large scale production. Once you assemble and solder numerous components, it will be expensive to redo defective parts at this stage. Component malfunctioning is mostly caused by poor placing of the solder mask. This article will help you to understand the solder testing well.

1. What is Solderability Test?

Solder is the material that you use to connect your PCB components. You need to carry out a solderability test to measure the solder wetting ability of the terminations. Once you know their wetting ability, it is easy to secure the connections. It is important to note that this is one of the most crucial circuit board testing methods. 

Assessing your components’ solderability will inform your PCB manufacturer whether the connected parts can tolerate the severe soldering temperatures. Besides, it also establishes whether keeping these parts can affect their ability to solder to the board. Generally, understanding the solderability of your components can reduce circuit board failures and enhance final product quality.       

2. Types of PCB Solderability Tests

You can determine the solderability of a part by determining its wetting ability. Solder wetting is the creation of a comparatively uniform, smooth, and continuous solder film. This film shows strong adherence to the soldered parts. Contrary to this, non-wetting is when the solder coat has partially stuck to a component. On the other hand, dewetting is the condition where the solder withdraws after covering a component. This forms uneven solder dunes but does not leave behind any exposed part.   

There are numerous types of solderability tests, but the most typical methods are:

2.1 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. Remember to conduct this step in a controlled manner using activated rosin flux. 

Lastly, inspect the parts according to the industry solderability standards. You should only consider your components to have passed the solderability test if fresh solder coats at least 95% of them. The coating, solder materials, and the test conditions determine the solder joint formation method.   

2.2 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). It then gradually increases beyond the zero axes, demonstrating that wetting has taken place.    

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.  

2.3 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.

3. The Benefits of Performing a Solderability Test

A solder test saves costs, and is an effective method of preventing poorly soldered components from reaching the final production.

Secondly, a solder test warranties proper electrical connections. This is because components that pass the test have reliable contacts and unbroken bonds. 

When using parts displaying good solderability, you can quickly reduce the solder temperature. That prevents component damage.   

Lastly, the components that have passed the test require short soldering temperature intervals. Consequently, this will preserve heat-sensitive parts.

4. Solderability Test Concerns

4.1 Is Solderability Testing Required in All PCB Projects?

You need to perform a solderability test during the various production process, like when:

  • Assessing the circuit board coat, solder, and flux.
  • Conducting quality control
  • Benchmarking. 

Generally, the test is essential in PCB projects. This is because contamination reduces the solderability of stored parts with time.    

4.2 What is the Cost of Performing a Solderability Test?

Most designers consider the solder test as a destructive process. However, the test ends up saving PCB production costs. As we mentioned earlier, poorly soldered surfaces call for reworking. This will consume your time and resources. Generally, solderability testing:

  • Minimizes assembly problems, such as solder mask misuses. 
  • Enhances the probability of quality solder joints. 
  • Validates safe storage. 

4.3 Which Solderability Tests do You Offer?

WellPCB offers all types of solder tests, including the dip and look method, the wetting balance analysis method, the surface mount simulation test, etc. We acknowledge that the test is an integral step of PCB functional testing. That is why we are always available to ensure that your PCB components pass the test quickly.

Final Thoughts on Solderability Test

A solderability test will help you measure your PCB components’ solderability. Generally, the test is an essential process in PCB projects. It minimizes assembly problems, enhances the probability of quality solder joints, and confirms safe storage. Importantly, when your electronic products pass the solder testing, they will definitely solder well in the final volume production.  

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Emma Lu
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