Jul 3rd, 2018
What finish should I use for my PCB Design? There’s no one single answer, it depends. Meet chemist and surface finish expert Mike Carano, the Vice President of Technology and Business Development at RBP Chemical, industry leaders in high performance chemical technology. Mike emphasizes a key question when it comes to surface finishes, “What are the reliability requirements of the environment?” Learn about the chemistry behind different finishes, fabrication and get tips for avoiding corrosion in unexpected environments in this episode of the OnTrack Podcast.
- Mike was Inducted into IPC hall of fame.
- RBP Chemical - veteran owned small business, based in Milwaukee, founded in 1954 as a supplier for the printing industry and over the years evolved into surface finishes and also carry product lines for Embedded Medical Devices and Semiconductor and Mining industries.
- On using solder mask over bare copper method - prior to going out to assembly the copper needs to be made pristine.
- What are the surface finishes and which to use when? 50% of industry using hot air solder leveling (HASL), a surface finish with a long successful history.
- Other surface finishes: Electroless nickel immersion gold (ENIG), Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG) - which is common in IC substrate, packaging industry.
- Future of surface finishes: Tin-silver, Direct palladium copper
- What finish should I use? There’s no one answer, it depends.
- Are there common examples of things that can go wrong? ie. High frequency design applications - ENIG is a well known issue that most engineers learn about the hard way.
- Where is the final product going to be used? Is it a domestic product or for the military?
- Reliability first, cost last. Cost should not be driving force.
- The environment is what really matters i.e. Shock-drop or Brunel fracture - consider for mobile phones, ENIG - tin-nickel bond, not tin-copper, corrosion environments, temperature extremes
- What are the reliability requirements of the environment?
- The most high quality board fabricators have strong process control and automation in place to ensure chemical stability.
- Board designers are looking for electrical performance. Need to ask about the environment.
- I would put every designer in a circuit board fabricator for a week and let them build a board they design.
- To learn, you need to practice and get practical information on building the bareboards.
- Creep corrosions on the mill automation machines because the OEM is specifying the finish.
- Japanese techniques i.e. Shokuku chemical
- Most substrate work is done in Asia; IC substrate packaging at its best is in Japan.
- Advice for learning: IPC courses, CID and CID+ training is one way to learn more.
Links and Resources:
HDP Users Group (HDPUG)