9 Common Printed Circuit Board Assembly Failures and Their Prevention Methods

Printed circuit board assembly

Failure 1: PCB Crack or Bend

The Reason:

Printed circuit board assembly (PCBA) may crack or bend because of high mechanical or physical stress. For instance, a rigid PCBA may fail if you put it to repeated vibrations or thermal shock. Also, even the flex PCBAs can crack if you apply a bending strength more than its capability.

Prevention method:

Before using the PCBs in the assembly process, make sure to prebake it and keep it in humidity-controlled cupboards. Will remove any water content in the bare PCB, which may cause shocks at the later stages of assembly.

(A technician fixing a broken PCB)

Failure 2: There is Apparent Polarity in the Components of the Assembled PCB

The Reason:

You may forget to mention the contradictions of the parts while designing the PCB layout. If the ingredients' opposition is not apparent on the printed circuit board assembly, it can cause issues of reverse polarity. For instance, if you connect a battery with reversed poles, it can damage the battery and the electrical parts. The printed circuit board assembly may also fail, and electrical shock may occur.

Prevention method:

You can either use a diode or a Schottky diode to mitigate the impacts of the reverse polarity. If you connect a diode in series with the battery, the circuit will shut off in the opposite polarity case. It will prevent any significant damage to the printed circuit board assembly.

（Electronic circuit board, Setup IC）

Failure 3: Solder Joint Fracture

Reason:

The difference in PCB's thermal coefficients and the electronic components may cause fracturing of the solder joint. The printed circuit board assembly may fail if you put it in an environment with repeated high or low temperatures. Another reason could be manual soldering, which makes solder more prone to heat stresses.

Prevention method:

It would help if you used specialized automatic machines for the soldering of the electronics components. You should not just put a small whisker of solder as it would eventually break due to vibrations. Therefore, make sure that the PCB has undergone visual inspection before sending it for the assembly process.

( Image: It shows a manually soldered PCB )

Fault 4: The Printed Circuit Board Corrosion

The reason:

Since the flux residues are used in this process, the printed circuit board assembly may corrode. The solder flux is obligatory for making sure secure connections of electrical components. However, it can also cause their corrosion once it comes in contact.

Prevention method:

The solder flux consists of organic acids such as citric or adipic acids. PCB assemblers should make sure that they eliminate any excess flux from the surface of PCB. In this way, there will be no flux left to destroy the metal contact. It touches on its way. If the PCB assemblers are using reflow soldering machines, they should remember to rinse off any extra flux.

( A white residue making the PCB defective)

Fault 5: The Component is Burned or Burned out (short circuit)

The reason:

During the printed circuit board assembly operation, short courses can damage both the PCB and the electronic components. It can be due to undetected solder bridges, moisture, or unexpected occurrences like high current spikes. The short circuits cause sudden and abrupt damage to the components. It may also cause a fire break out and damage to electrical equipment.

Prevention method:

Perform visual inspection for checking the short circuits on the PCB surface. For inner layers, electrical testing works best for printed circuit board assembly. This test will mainly inspect for any short or open circuits. Further, you may also compare the readings obtained with the ones obtained from probe tests.

Also, while designing the PCB layout, the PCB assembler must accurately align every layer. This way, they will be able to work in tandem and avoid any short circuits. You may also reduce the thickness of the PCB stencil to decrease the solder paste deposition.

( A burning PCB due to short-circuit )

Fault 6: Copper Weight is not Suitable

The reason:

For good electrical flow in printed circuit board assembly, correct copper foil weight is necessary. If the copper weight is either too thin or thick, it will cause your printed circuit board assembly's failure. This occurs because of improper size determination and trace width selection while designing the PCB layout.

Prevention method:

The PCB assemblers must follow the copper weight specifications required by the designer. It should be neither too thick, as it can increase costs, nor too thin, as they may result in heating of PCB.

（Hands of engineer with a digital multimeter check computer electronic circuit board）

Fault 7: The Component Position Has Moved

The reason:

In printed circuit board assembly, pick and place or some other automatic machine places the board's component. If the component shifts or moves due to the molten solder during soldering, your printed circuit board assembly will fail mainly because a reliable solder joint will not develop and may result in an open circuit.

Prevention method:

PCB assemblers should follow the standard humidity and temperature requirements. They may use a more accurate pick and place machine for precise placement of components. Further, if you also use a more aggressive flux, it will improve the parts' solderability. It will make them stay in their original position.

(Manual placement of components)

Failure 8: Component Warranty May Be Less

The reason:

If any individual component fails in the printed circuit board assembly, it can cause the collapse of the whole PCB assembly. The parts may fail due to adverse selection. It would help if you made sure that the components do not have a limited warranty. Also, if you select a low-quality component, it will decrease the life of the parts. They may fail even before their warranty expires.

Prevention method:

You should carefully select the components or ask your PCB assembler to do so. The part should not be damaged or low quality. Further, you may also make sure that they are available in abundance, so that may they fail, you can repurchase the same components.

(Various electronic components are shown)

Failure 9: De-wetting Due to Melting Solder

The reason:

Dewetting occurs due to a problem with electric components or the solder pad. If it happens, the solder joint will be loose, and it will not make a secure connection with the element. The two main reasons for dewetting are contamination, corrosion, and the following overheating. So, if the component leads are without solder, your PCB assembly will fail.

Prevention method:

The PCB assemblers must perform careful board examination, prepare it well, and then do the necessary cleaning. The pencil eraser eliminates any mild corrosion or rust. You can identify the matt copper pads by their dark brown color. The solder does not stick to the surface affected by rusty must apply it after cleaning, and get rid of the excess with solder wick.

You can also use magnification glass for checking the conformal coating. A hobby knife will easily remove them. Further, please keep your fingers well away from repair areas, and handle the boards by their edges. It will prevent contamination. The salt on the skin can make the copper tarnish rapidly. And, the skin oil will disrupt the solder connections.

(Assembling PCB)

Summary:

In a nutshell, you will significantly reduce the nine common PCB assembly failures if you follow the given prevention methods. Your PCB will work fine, and there will be no re-assembly costs. However, you also need to ensure that your selected PCB manufacturer also has experts to produce high-quality boards. They should have all the advanced machines to follow the best practices for printed circuit board assembly.

Every PCB assembler may encounter challenges; but, we, here at OurPCB, have expert technicians to recognize printed circuit board assembly problems at early stages. Identifying them early helps us to provide you with quality boards. Contact us now if you are looking for preventing common PCB assembly failures.

OurPCB is willing to provide services on PCB and PCBA. You may ask for an online quote or email us to get in touch with our engineers.