Circuit Board Repair


[Circuit Board Repair | The correct way to fix PCB]

The most used equipment for circuit board maintenance is DMM (digital multimeter) and oscilloscope. These equipment are the most basic equipment used to check the simple PCB structure. They can measure the voltage and waveform of the test point of the circuit very well. But with the proliferation of high-end electronics, these simple devices face significant challenges. In order to reduce the cost of PCB inspection, enterprises provide PCB consistency through automated equipment. For electronics enthusiasts, it is inevitable to encounter circuit boards that need to be repaired in a large number of DIY circuits. When they face these failures, do they deal with them by themselves or seek help from PCB Repair companies?。

FS PCBAbelieves that today's electronic circuits are more complex than ever. Whether design failures, manufacturing failures or assembly failures have become commonplace. Circuit boards that have been used for a long time often lead to PCBA failure due to component failures such as electrolytic capacitors. For newly-produced PCBAs, there are often manufacturing failures, false soldering, and missing soldering due to operator errors, causing the circuit board to fail to operate normally. For this reason, we need to take certain measures to conduct PCBA failure analysis to ensure that the assembled PCBA can operate according to the intended function.

While hand soldering is more suitable for hobbyists or small batch orders, some repairs may require a more professional approach to finding the cause of the failure. Repairing a complete PCB assembly can seem daunting, but a methodical approach helps to find and fix problems quickly.

We believe that the best repair measure is to obtain a circuit board failure analysis report from the customer. Is it working properly? What are the obvious symptoms of the fault? Was it just running a software update that caused the glitch? PCB working environment?

When we find that an electronic product cannot operate, it is the most sensible choice to cut off the power immediately. When a fault occurs, the first reaction of ordinary people is that the fuse is blown. We need to face up to this problem, such as replacing the fuse with a higher resistance. The circuit board short is often caused by excessive current, and it will have obvious phenomena, such as heating, burning smell, etc.

For some PCBs with special surface treatment, we need to clear these faults first. Historically, electronics manufacturers have asked us to apply conformal coatings, which protect against moisture and dust, and we need to remove them. FS Technologies conformal coatings can be removed using solvents, stripping or sandblasting, and many companies are also working on new techniques to pierce the coating with very sharp test needles.

Information collection will be helpful for the repair work. Before officially starting the repair, we will use digital multimeters, soldering/desoldering hand tools, oscilloscopes, power supplies, etc. to test the circuit boards that need to be repaired. The most useful "tools" are user reports of how failures occur or observed failures.

According to the complexity of the circuit board circuit structure, we choose different equipment for this work. The most commonly used one is a multimeter. If you are an electronics enthusiast, we recommend that you buy one. For PCBA factories, we often need to deal with high-frequency boards with more complex structures, IMS boards, etc. For these PCB tests, it may be necessary to use LCR meters, oscilloscopes, power supplies and logic analyzers to investigate the operation of the circuit. For RF circuits it may be necessary to use a spectrum analyzer.

Below is a complete PCB rework strategy. Troubleshooting is also much easier if a known good board is available so that visual and signal comparisons can be made. The lack of comparison boards or documentation compounded the challenge.

Artificial Vision Inspection

In addition to circuit board failures at the technical level, PCBA components may fall off due to severe vibration in the transportation diagram, so manufacturers often use more complete transportation methods. When we receive the goods, please check in time whether the connectors or components in the socket are loose, whether there are components falling, etc. We call this detection method PCB manual inspection , that is, to use a microscope or a magnifying glass to find. This method is considered to be an effective and indispensable detection method, but it is limited by the technical means of the operator.

PCB capacitor detection

If you observe obvious leaks, cracks, bumps, etc. on the PCB, it may be due to damaged capacitors on the PCBA board. A capacitor is a circuit board component with a short lifespan. When the lifespan is reached, please replace it with a capacitor with an equivalent or rated voltage.

Wire breakage

SMD is widely used on PCBA boards, but due to the small size and small pins of these components, they are easily broken due to pressure. Among all SMD components, integrated circuits are the most expensive and most vulnerable components. If the PCBA processing factory does not control the pressure of the placement machine when assembling these fragile SMD components, it is easy to cause IC bending. Use a microscope to look for cracks on circuit boards that result in broken circuit traces or damaged components.

Component burnt

The role of the circuit board is to provide electrical connections between electronic components as a carrier. These components are very fragile, and even static electricity generated by contact can cause a breakdown. When the current is too large, the components are easily burned, so we need to check whether the transformer, power output transistor, resistor, capacitor, etc. are burned. With this type of damage, overheated components can be identified by burns and brown stains, but you need to find out why they overheated.


PCB assembly is a complex and professional process, and failure in any link will lead to PCBA failure. In order to avoid loss of reputation, PCBA processing factories usually add testing procedures in every link to ensure the integrity of PCBA.