Surface Finishes Are Used on Fast Turn Printed Circuit Board Assembly
A fast turn printed circuit board assembly is an effective way to reduce overall production time. Keeping this in mind, you should start planning your fast-turn project early with your assembly partner, ideally as soon as the design and gerber files are complete. This allows the fastest possible time for programming, documentation review, part sourcing, and preparation of pick-and-place data.
The type of surface finish used on a fast-turn printed circuit board plays an important role in the performance and cost of the finished product. Choosing the right surface finish requires careful consideration of factors like tight pitch components, heat dissipation, sensitivity in handling, lead related compliance, shelf life and more. The correct choice of surface finish will ensure your finished product is durable, efficient and reliable.
The most popular fast turn printed circuit board assembly surface finish is Hot Air Solder Leveling (HASL). This traditional technique involves dipping the circuit board in a molten solder bath to encase all exposed copper surfaces with an alloy of tin and lead. Once the excess solder is blown away with hot air knives, HASL offers a low-cost option that is ideal for simple and straightforward applications. If your application has strict requirements for environmental or lead-free compliance, you can choose a version of HASL called Lead-Free HASL. This offers all the benefits of HASL but eliminates the use of lead, making your circuit board compliant with RoHS directives.
What Types of Surface Finishes Are Used on Fast Turn Printed Circuit Board Assembly?
Chemical or metal immersion surface finishes, including tin, silver and gold, are another common option for your PCBs. They offer a flat finish, excellent solderability and heat dissipation, but are more sensitive in handling and have a shorter operating window. They are also more expensive than HASL.
Electroless nickel immersion gold surface finish is a popular choice because it offers the best balance of value and quality for a wide range of applications. The gold plating is both hard and wire bondable, and it provides good thermal conductivity and resistivity. Electroless gold is also very durable, increasing the operational life of your boards.
ENEPIG is a variant of the electroless nickel surface finish that includes a palladium layer to prevent “black pad” corrosion. It also adds a layer of immersion gold to provide protection for the nickel layer. This provides a high-reliability solution, especially for high-speed or harsh-environment applications.
If your project has specific requirements that require a more durable surface finish, consider carbon or ENEPIG. These options can be more costly, but they deliver durability and longevity that will save you money and resources in the long run. As you weigh your options, keep in mind that the right surface finish is just as important as the material used to create your bare boards. Taking the time to think through your needs, and working with an experienced assembly provider, will allow you to get the most out of your fast-turn printed circuit board.