Top Tips for Flex Designers from a Fabrication Perspective
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Sometimes, it can seem like designers and fabricators are speaking two different languages, and maybe they are! But both are working toward the common goal of producing a high quality, reliable, and repeatable printed circuit board. “Back in the old days,” it was common for designers and fabricators to meet face-to-face on a regular basis. Designers became familiar with and understood the basic fabrication processes, including where different design attributes could be challenging for fabrication. At the same time, fabricators were given the opportunity to talk to designers and understand the challenges they face when creating a new design, and why it’s sometimes necessary to push the envelope.
This sort of open dialog isn’t nearly as common today for many reasons. There has been a significant decline in the number of PCB fabricators, making visits more difficult and often involving travel. Also contributing to this transition is the boom of the digital age. We are all accustomed to information being available at our fingertips and quick replies via email, and we tend to spend much less time in verbal discussion.
Thinking about this communication or knowledge gap, I am kicking off a short series of blogs, speaking directly to flex and rigid-flex fabricators and asking them a few questions probing for specific items that they think are important to share with designers.
For this blog post, I reached out to Anaya Vardya, CEO of American Standard Circuits. Anaya has extensive experience in virtually every aspect of the PCB manufacturing operation, including supply chain management and quality control. It is this background that allows Anaya to not only serve as ASC’s CEO, but as an expert ready to assist with whatever questions you may have. His thoughts are included below.
What do you wish every designer knew about flex, and why?
Material Selection is absolutely critical. Calculating the thickness of the flexible portion of the design is key, and what this thickness needs to be depends on many things: how is the flex going to function, what is the possible bend radius, and will this design be flex to install or dynamic flex? Additionally, there are flex materials which meet UL standards and flex materials which will not, and flex laminates bonding copper to dielectric with adhesive and without adhesive. All of these things factor into the overall thickness and potential bend radius.
Often, fabricators will see specific “brand” names called out on a drawing which limits the manufacturer to that specific flex laminate supplier. This can be a problem since different flexible PCB manufacturers may have different preferred material suppliers they use. This is especially important if the flex design may potentially be transferred to offshore manufacturing since domestic flex materials are likely not available offshore. It is always best to refer to IPC requirements for your material callouts.
What is your best advice to someone just starting with flex and rigid-flex?
Engage a knowledgeable PCB flex manufacturer as early in the design process as possible. The manufacturer should be happy to help with proper material selection, identifying cost drivers in the design and providing suggestions to reduce the overall cost and recommend the best panel layout for fabrication. Understanding the dos and don’ts before the design is completed can save time and expense by avoiding costly modifications once the design is complete.
What is the key difference in the fabrication process when working with flex materials as compared to rigid materials?
The most significant difference with manufacturing is usually material handling. The flex materials are extremely thin and not glass-reinforced, so they can easily become damaged by poor handling methods. Flex fabrication requires stringent material handling procedures including picking up materials only by opposite corners. It also requires custom trays and other transportation methods, and necessitates taping the flex materials to leader boards prior to running through certain equipment to be sure the thin flex panels are not caught up in equipment rollers and damaged.
Flexible circuit materials also absorb moisture at greater rates than standard PCB materials, so additional baking is usually required and may need to be done before certain processes. HASL is one example in which a flexible circuit panel will require baking prior to processing and an FR4 panel may not. Because the flex material is not reinforced layer to layer, registration is also always a concern and additional tooling may be required to ensure a reliable and repeatable process.
Wrapping up, I want to thank Anaya Vardya for participating and answering these questions—giving insight into some of the bigger issues that flexible PCB fabricators deal with. I also encourage you to please reach out to us or post a comment suggesting questions that you would like to see answered in future blog posts!
Would you like to find out more about how Altium Designer can help you with your next PCB design? Talk to an expert at Altium or read more about flex and rigid-flex PCB assembly in Altium Designer®.