What Does Reworked PCB Mean?
Rework Tasks Typically Fall into One of Two Categories
The first category, needs to solve the problems in the design.
Your schematic symbols do not match the PCB footprint
You have chosen the wrong resistor value.
You chose the wrong IC
You forgot to make the necessary connections between the two pins
In the second category, the design needs to be changed.
You need to create a new function
you need to change the specs
You need to switch components
In the former case, there is an error in the design or assembly process, so a component or PCB trace needs to be changed to fix it.
In the latter case, the intended design works, but it turns out that it is no longer required by the product, so changes to components or PCB traces are required to adjust the design.
PCBA rework primarily involves heat and soldering, but may also require mechanical operations such as cutting traces or modifying physical components.
When designing a printed circuit board, you may not often consider how your design choices affect future rework operations. But rework is often necessary during prototype board startup, testing, or deployment.
PCB Rework and PCB Repair
You may be looking at the above and thinking that “fixing a problem” in a PCB is the same as PCB repairing. The difference comes from where the error occurs. Repairs are usually done when a circuit board fails for a specific reason. ESD strike or reverse polarity connection possible. This means that repairs are necessary because of unexpected failures.
Rework, on the other hand, means there are design errors that need to be corrected.
6 Tips for Reworking PCBs
Make your PCB bigger
Prototypes rarely need to be as small as the final design, so make the prototype PCB larger and fit it into an off-the-shelf prototype enclosure. This will allow you to release designs faster and waste less time on tricky PCB layout issues. To test as part of a system, use cables to connect a larger prototype PCB to a compact point in the system. Larger PCBs are easier to use on the bench, easier to probe, and easier to rework.
Use Larger Components
While using tiny BGA components or 01005 package resistors might look cool and advanced, you probably don’t need them – and your prototypes definitely don’t. You can’t easily rework parts smaller than a grain of sugar. For prototypes, unless absolutely necessary, consider using parts no smaller than 0402 and using parts with exposed leads whenever possible, rather than BGA or QFN packages.
Allow More Clearance
Rework is easier and more reliable when there is more clearance around the part. For BGA, QFN or other packages with no exposed leads, it is critical to have enough space around them for local rework reflow heating. For high-density or press-fit connectors, clearance is required for tools that utilize the PCB. Clearance is important for mechanical parts such as radiator snap-in pins, hand tools such as pliers.
Layout Strapping Resistors and Jumper Options
The goal of a circuit designer is to design everything right the first time. However, you can save a lot of time and hassle by designing bundled resistors that let you pull all the setup pins high or low with a simple rework. Or consider adding additional unmanned filter circuits around your power regulator. You can even design entire secondary circuits by simply moving jumpers from one header to another.
Use Programmable Parts
Where possible, use programmable parts for rework flexibility. Adjusting firmware is often easier than cutting traces or re-soldering components. Look for places where a programmable voltage regulator, microcontroller or CPLD/FPGA might make sense in your prototype, even if that’s not the intent of your final design. Simple, inexpensive programmable parts allow you to redesign your designs without compromising hardware.
Install All Programming Headers
Not following this guideline has troubled many, many designers. Spend a few extra cents to install every pesky programming header. Experience has shown that this works well if you install all programming headers on the prototype.
Follow these six tips and save your time and budget.
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