Final Quality Control (FQC) in PCB Manufacturing

A circuit board is the most important component for designing a smooth-functioning electronic device. A printed circuit board is the heart of the device because it can implement the performance and functions of electronic gadgets. However, PCB assembly creation involves a complex process, and manufacturers need to pay attention to every detail. Let us now see how they conduct a quality assurance process to provide the best products.

Final Quality Control involves a process that meets quality requirements. Experts will examine every manufacturing step, starting from the original design to the end-product verification.

Conducting a Final Quality Control process for the circuit board manufacturing project is crucial for several reasons.

Prevent Device Failures–

A malfunctioning and defective PCB will cause failure to your electronic device. Even a single or minor flaw can result in short circuits. It can also pose safety risks to users. During PCB manufacturing, professionals have to inspect the design to identify errors and correct them.

Promote Brand Reputation–

The best PCB companies provide proof of Final Quality Control to maintain the reputation of their business. They want to show that their only aim is to provide quality products. This effort enables them to boost their sales and gain loyalty from customers.

Save Costs–

By conducting Final Quality Control in PCB Production, manufacturers can identify errors earlier. They can repair or rework the defective components. Thus, it will reduce production costs and save overall time, making the business more profitable in the future.

Ensure Better Customer Satisfaction 

PCB manufacturers want to satisfy customers with high-quality products. So, the quality control process helps manufacturers increase the customer satisfaction level.

Comply with Regulatory Standards 

In an electronic equipment production project, manufacturers should adhere to different standards and rules. The finished product must comply with industry standards. Failure to do so will lead to legal issues.

Important Criteria For Inspecting PCB Boards

 PCB manufacturers set some criteria for checking the quality of the circuit boards.

• Visual qualities- Manufacturers need to ensure that the board dimension is correct and there are no plating flaws. Besides, there should be perfection in the conductor spacing.
• Quality of solder mask- The mask should not have discoloration, scratches, or residues. 
• Cleanliness- No residues should contaminate the PCB.
• The PCB needs to undergo an electrical test. It involves testing the resistance, capacitance, and adjacency of the product.
• Experts also check the prior defect history of the product.

What Are the Ways to Check PCB Quality?

FQC in PCB Manufacturing involves different testing methods.

Visual Inspection–

If a PCB is not properly cleaned, a visual inspection will show white residues on the surface. Exposure of these residues to chemicals and heat makes them appear white. Visual inspection of the PCB is an affordable method. Although it is just a qualitative method, it is best for class 1 electronic gadgets. Only bare human eyes will detect visible flux, dendrites, and white residues. But, magnifications are essential for high-density boards.

However, human eyes may miss many micro-level defects. Besides, not every inspector has the same level of skill. That is why automated inspection processes are better to improve and maintain consistency. You should note that FCQ is different from PCB. FCQ provides good testing to find almost any defect that has not been considered during visual inspection.

Automated Optical Inspection- A Final Quality Control Process 

AOI is a machine-driven process for testing and evaluating PCB to identify potential errors like dimensional issues, surface defects, and component placement problems. As PCBs are highly complicated, it is challenging to check them manually. That is why AOI is the best method for checking PCB after assembly. 

The AOI testing process is not just for PCBs but for PCB assemblies as well. The test identifies potential defects, such as insufficient solder and shorts. But, in the case of the PSB assembly, the process will detect polarity, values, and component soldering. With the AOI test, engineers want to improve the PCB’s pass rate and reduce the overall cost.

AOI tests for your PCB board will also inspect

• Billboarding
• Component absence or presence 
• Excessive solder joints
• Component skew
• Height defects
• Flipped component
• Lifted leads
• Paste registration
• Damaged parts
• Volume issues
• Solder bridging

Testing Cleanliness of the PCBs

The Final Quality Control process involves checking the cleanliness of the PCB to determine the amount and type of contaminants.

There are different types of cleanliness testing conducted for PCBs.

Ionic contamination test– 

Ionic contamination causes a high risk to the performance and integrity of your PCB assembly. It occurs when highly sensitive and conductive devices get exposed to different contaminants during the assembly and fabrication process. Salts, sulfates, acids, and other residual substances are the main reasons for contamination. The Final Quality Control team will use an omegameter and contaminometer to measure ionic cleanliness. Ions are released to mix them with an extraction liquid. The test determines bulk ions in a square inch.

SIR Testing–

Dendrite formation, leakage, and electrochemical migration result from contamination. It will then affect the surface insulation resistance of your printed circuit board. That is why SIR testing is essential to check the conductivity of ionic residues. The test will show the resistance to the current flow of charge. If the test shows higher resistance, it indicates a clean board. 

Electrical Testing Methods for PCBs

An electrical check for PCB involves different testing techniques-

Flying probe testing- It is a cost-effective process that checks for resistance, shorts open, diode issues, capacitance, and inductance. This testing process needs to use needles fitted to a probe. But, if you have placed a large order for PCBs, the flying probe process will be costly.

In-circuit testing–

 ICT is one of the robust testing processes implemented for PCBs. The overall cost varies with the size of the fixture and board. ICT powers up every circuitry on your board. The best fact is that the test ensures 100% coverage. Experts will lay out fixed probes in a way that aligns with the PCB design. Besides, the probe inspects the solder connection’s integrity. The ICT tester pushes down the board to initiate the test.

Different functional tests for PCBs–

A functional test for PCB verifies the behavior of the board in the end-use environment of the product. However, the needs for functional tests and processes vary considerably by PCBs. 

Other types of PCB assembly testing processes include

• Solderability tests check the sturdiness of the surface and boost the formation of solder joints.
• Micro-sectioning evaluation investigates shorts, defects, and other risks of failures.
• Solder float test is another process to identify the thermal stress level that can be resisted by PCB holes.
• Peel test- It detects the level of strength needed to remove the laminate from PCB.

PCB functional testing processes are highly advantageous because they simulate the working environment and reduce cost. They also eliminate the need for conducting costly tests for the system. Most professionals pair different testing processes like flying probes and ICT to provide the best result. 

Conclusion–

The best PCB manufacturers ensure that they have implemented Final Quality Control processes for every board. So, you will find an acceptable quality level of the boards. You can look for reliable PCB fabricators and suppliers to make an optimal approach.