The devices that we commonly utilise to perform specific tasks contain printed circuit boards or PCBs inside. Manufacturing of these circuit boards has grown across many areas in the world, mostly in the Asia Pacific region, due to the escalating demand for electronics. Having sufficient capacity and technical expertise to produce these PCBs is extremely important to achieve a stable supply chain.
Errors and variations during PCB fabrication and assembly are possible due to several factors such as inconsistencies in materials, processes and machines. The processes have become complex as devices become smaller and denser. Printed circuit board repair is a common practice as it can be done successfully without impacting the performance of the boards.
When a PCB fails, the most practical approach is to know the underlying defective part and replace it rather than replace the entire PCB. This article discusses guidelines to refer to when performing printed circuit board repair. These include the Do’s and Don’t’s that must be followed to avoid encountering further defects on the PCBs.
What is Circuit Board Repair?
Circuit board repair refers to the restoration of a defective device by replacing a defective component with a good part without damaging the functionality of the PCB. It consists of the following steps:
- Inspection of the failing PCB to examine physical and functional damage
- Removal of the Component through desoldering techniques
- Preparation of the circuit board surface by ensuring a clean and smooth surface for the soldering process
- Solder paste and/or flux application to achieve an oxide-free solder joint. Flux can remove the oxides during the soldering process by chemically breaking the oxide film.
- Alignment and placement of component
- Soldering of the component
- Visual inspection of the soldered component and electrical testing
Some issues can arise during circuit board repair; thus, it is noteworthy that guidelines are followed while errors are prevented during circuit board testing and repair. These are the known issues that can happen:
- Electrical Overstress: Electrical overstress or EOS is a catastrophic device failure caused by mismanaged voltage or current that can cause circuit failures. Using tools that are not safe for handling components and incorrect soldering methods can result in EOS.
- Poor Connection: Electronic board repairs without following the right soldering parameters can result in insufficient connection between the component and the circuit pads.
- ESD Damage: Electrostatic discharge or ESD is a phenomenon wherein static charges interfere with the electrical performance of the device. Only tools and equipment that comply with ESD standards should be used during circuit board testing and repair.
Do’s in PCB Repair
Now that we understand the different steps in circuit board repair and the common issues, let us discuss the guidelines for the proper execution of PCB board repair. The expectation in PCB repair is to correctly identify and correct the defect and to eventually come up with a PCB that is as good as new.
- Pre-heating of the PCB. Sudden application of heat to the component’s solder joint can lead to thermal shock. The PCB should be preheated first at high temperatures for a certain period to avoid thermal stresses from trapped moisture. A tailor-designed fixture is used to hold the PCB prior to reflow. With pre-heating, the warpage of the PCB is also prevented through a gradual ramp-up of temperatures. Through the pre-heating step, PCB
- Follow Industry Guidelines. International standards should be followed in PCB repair. These standards offer requirements such as correct temperature, acceptance criteria and testing methods to have a reliable PCB post-repair.
- Perform Post-inspection of the Repaired Circuit Board. After the PC board repairs, a visual inspection is necessary to check if the solder joint has been successfully formed. For some important active components, x-ray inspection is also important to verify the full coverage of the solder. A certificate of conformance (COC) must be issued as evidence and documentation that the electronic circuit board repair has been effectively completed.
- Make Sure that Sufficient Solder is Applied. The soldering volume must be sufficient and uniform to avoid shorting with adjacent components. Insufficient soldering volumes can lead to non-soldering and detaching issues. Correct pressure parameters during electronic circuit board repair are necessary to get a reliable solder finish.
Don’ts in PCB Repair
Some mistakes should be avoided when conducting PCB repairs. These mistakes can result in higher expenses. Being aware of these errors can save a lot of cost and resources.
- Do not Disturb Other Components. During electronic board repairs, neighbouring components must be left undisturbed. To repair PCBs, there are further damages if one is not careful in de-soldering and re-soldering of parts. The inspection of the PCB after repair must also include the other components to check if there have been damages incurred.
- Do not Overheat the Board. Specifications must be established as to the right temperature range to follow when performing PCB repairs. Excessive heat can affect sensitive components that can aggravate failures on the device. Vulnerable components must have a thermal shunt to channel the heat away from the component.
- Do not Allow the Movement of Components during Soldering. The alignment and proper attachment of the component are crucial for good PC board repairs. Movement of the part during soldering should be minimised so that a metallurgical bond between the part and the pad is achieved.
- Do not let Untrained Personnel Perform PCB Repair. PCB board repair requires both knowledge and skill which can be acquired through technical training. Allowing untrained personnel to perform PCB repair can lead to serious events such as safety risks, quality non-compliance and reduced productivity. The solder connection must be smooth and free from dents and blistering which will require workmanship.
- Do not Skip Inspection and Testing. Inspection and testing are highly essential to properly evaluate the effectiveness of the printed circuit board repair. IPC standards provide test methods to repair PCBs that must be followed. These steps help to know if there are weak solder joints and misaligned parts.
