PCB Assembly Rework

PCB assembly rework comprises de-soldering or re-soldering of certain surface mounted components on the board. So, the term implies repairs or replacements required on a PCB. However, there are some challenges involved. For instance, unlike PCB production, rework cannot be mass produced. Hence, there are cost and time issues involved when it comes to PCB assembly repairs, and if it is lead-free assembly, the cost rises further. Sierra Assembly Technology, Inc. offers various types of PCB assemblies and relevant services including rework and repairs. We do not compromise on quality, while adhering to the strict deadlines.

PCB Assembly Rework Process at Sierra Assembly Technology, Inc.

There is not much difference in the process for leaded or lead-free PCB assemblies, except that lead-free assemblies require higher temperatures and a better precision. It is crucial to clean the PCBs before rework or component removal. Here are the steps followed for PCB assembly rework:

1. Thermal profiling: This is done to determine the actual component temperatures, as well as identify the soldering process required for a given PCB assembly.
2. Removal of damaged components: Depending on the component, special and safe tools such as forked tips, wooden sticks, or tweezers are used to remove damaged components. Various heating methods are used. Any component should be removed as quickly as possible. Special care needs to be taken for glued components, and extra heating with a tip may be required until the glue comes off completely. Liquid flux is applied to both ends of the component and the forked tip is placed on the top of it. Once the solder is melted, the component slides away from the site and is picked up from the board.
3. Cleaning of the site: Cleaning is crucial before, as well as after soldering and component removal. The liquid used, oils, and grease should be thoroughly removed as these may create issues such as poor adhesion and contamination.
4. Removal of rust and solder residues: Soldering leaves behind flux residues such as ionic contaminants which depending on their charge increase the conductivity of the cleaning solution. This may cause current leakage issues and corrosion. Hence, it is important to remove these residues.
5. Replacement of the component with a new soldered one: Replacing a new component is a crucial task and even tougher than removing a component. This requires highly skilled technicians and upgraded equipment. Usually epoxy liquid is used when replacing surface mount pads or circuits. However, it is not suitable for fine pitch components. Certain pads come with adhesives and they are heat bonded to the board surface.
6. Testing and inspection: The PCB assembly once repaired is tested, operated, and verified by authorities from all aspects such as required functionalities, quality of components used, contamination or other drawbacks, and so on.

Factors Considered before PCB Assembly Rework

As mentioned above, there are cost and time issues involved and quality cannot be compromised upon. Many factors play a role in how a PCB is reworked upon. Here are some of them:

• Material used, thickness, complexity, and type of components are some physical factors considered.
• PCBs today are pretty complex with fine-line circuits and precision components. It is essential to figure out how much conformance to the original component is required in the reworked component.
• The complexity and size of the electronic device in which the PCB is to be fitted is important, whether it is a general, dedicated, or high-performance electronic device.
• The type of PCB, whether rigid, flexible, or rigid-flex, needs to be considered.
• Mounting of certain components needs to be done manually and requires excellent skill. Hence the skill level of the concerned technician also needs to be verified.
• The quality of tools used for soldering, heating, drilling, removing components, and so on is important as well.
• Appropriate work areas, free from contamination and dust, must be designated for PCB assembly rework.
• It is essential to identify the original coating on the component to be able to choose an appropriate coating removal method such as heating, scraping, and so on.

With over 30 years of experience in handling PCB assembling requirements across diverse industries ranging from defense to healthcare, Sierra Assembly can assure high-quality PCB assembly services and has standard and documented methods and practices for PCB assembly rework. We also have certified, skilled technicians who have vast experience to their credit.