All About Flex: Process Controls for Flexible Circuit Fabrication

Reading time ( words)

Manufacturers of flexible circuits use several chemical processes for fabrication. These processes are generally located in a common area of the plant because of facility requirements and environmental considerations. These chemical operations are referred to as wet processes. Some of the specific processes that would be characterized as wet process in circuit fabrication:

• Develop-etch-strip: Photosensitive resist is developed so the unneeded resist is washed away, leaving a pattern of resist that defines the circuitry. The subsequent etching operation removes the base metal (normally copper) that has been exposed by the patterned resist. The last step is to remove (strip away) the resist that defined the circuitry.

• Copper plating: This is typically an electro-chemical operation. Metal is electrodeposited onto the base metal surface thereby creating a thin, robust coating. Electroplating of copper is the most common example and is used to create electrical connection between traces on the top and bottom of the insulating dielectric film.

• Shadow plating: A laminate of metal-dielectric-metal is initially drilled, punched, or laser ablated to form the vias. In order to initially create an electrical connection between the layers of metal, the dielectric must be coated with a conductive material. Shadow plating coats graphite inside a via and is a chemical process commonly used by flexible circuit manufacturers.

Each of these operations relies on chemical reactions, which may be supplemented with mechanical agitation, temperature and voltage/current. In most cases the chemical makeup is the most critical element that affects the output. It is vital that critical process parameters are tightly controlled to assure desired results. The following are the basic outputs that are monitored and compared to a process or customer specification:

  • Trace width and spacing
  • Metal thickness
  • Via integrity
  • Metal composition

To read the full article click here.

Editor's Note: This article originally appeared in the November 2015 issue of The PCB Magazine.


Suggested Items

EIPC Summer Conference 2022: Day 2 Review

06/29/2022 | Pete Starkey, I-Connect007
Örebro, Sweden on June 15 brought a bright and early start to Day 2 of the EIPC Summer Conference for those who had enjoyed the previous evening’s networking dinner, but had resisted the temptation to over-indulge or to carry on their long-awaited catch-up conversations with old friends into the small hours. All but a few were in their seats for 9 a.m., awake and attentive for Session 4 of the conference, on the theme of new process technologies, moderated by Martyn Gaudion, CEO of Polar Instruments.

EIPC Summer Conference 2022: Day 1 Review

06/28/2022 | Pete Starkey, I-Connect007
At last, a live EIPC conference and this time in the Swedish city of Örebro, “where history and contemporary culture converge,” a pleasant and convenient location for an event that included a privileged visit to the Ericsson facility in Kumla. Around 100 delegates made the journey and the Örebro Scandic Grand Hotel was an excellent conference venue for the June 14-15 conference.

PCB Plating Still Comes Down to Physics

06/21/2022 | I-Connect007 Editorial Team
We asked columnist Michael Carano to discuss the latest innovations in plating equipment and chemicals, as well as some of the drivers in this segment, and the biggest challenges and opportunities he sees in plating today. As Michael points out, despite all of the technological advances in this industry, process engineers still need a solid understanding of Faraday’s Law and Ohm’s Law to successfully plate PCBs.

Copyright © 2022 I-Connect007. All rights reserved.