Choosing the Right Printed Circuit Board Finish
An often-overlooked decision in designing printed circuit boards is which surface finish is the best choice for the project. At least nine different choices are commonly available. Thinking through some factors will help you make the best decision.
Lead-Free Solder
Depending on where the product will be used after PCB assembly, you may face government regulations on the type of solder used in the project. Choices include:
- Lead-free hot air solder leveling
- Organic solderability preservative
* Immersion silver
- Immersion tin
- Electroless nickel immersion gold (ENIG)
- Electroless nickel
- Electroless nickel electroless palladium immersion gold
- Electrolyte wire bondable gold
- Electrolyte hard gold
Denotes BESTProto preferred finishes
Tight Pitch
Pitch refers to the center-to-center spacing between conductors, such as pads and pins. If you have a project, such as ball grid arrays, where that space is extremely minimal, it is vital to choose the right finish. Making a poor decision often leads to weak connections.
If you need a tight pitch, consider:
- Immersion silver
- Electroless nickel immersion gold (ENIG)
- Electroless nickel electroless palladium immersion gold
Shelf Life
Many different factors determine the shelf life of PCBs. Keeping the boards in a low-humidity environment that is dust-free helps extend their lives. Choosing quality materials for the PCB assembly can help. High frequencies and high loads on PCBs can make them fail more quickly. Boards should be stored in an environment that is colder than 30 degrees Celsius and has less than 85% relative humidity.
When shelf life is one of the deciding factors, choose:
- Hot-air solder leveling (HASL)
- Lead-free hot-air solder leveling (Lead-free HASL)
- Immersion silver
- Immersion tin
- Electroless nickel immersion gold (ENIG)
- Electroless nickel electroless palladium immersion gold
- Electrolyte wire bondable gold
- Electrolyte hard gold
Extra Costs
Some raw materials can be more costly to obtain. The manufacturer must pass these costs on to the company using the PCB. The market can change rapidly, but some types of PCBs that typically come at a higher cost include:
- Electroless nickel electroless palladium immersion gold
- Electrolyte wire bondable gold
- Electrolyte hard gold
Considering these different factors can help you make a more informed choice based on your specific needs. Contact BESTProto, and we will be happy to discuss the specifics of your PCB needs with you.