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Application: Design guidelines to improve the flexibility and reliability of flexible circuits.
Most issues that arise with flex circuits can be eliminated in the early stages of the design phase, and special planning must occur when the circuit is required to bend. Many novices will design a circuit that calls for bending the flex in too tight of a bend radius, which can cause damage to the circuit and lower the reliability of the end product. This is the third and final installment in a series of articles that will focus on the seven key aspects to consider when designing for maximum durability and maximum “flexibility." It is important to know that because flexibility is a relative term this study will instead use the term reducing bend radius. Below are three of the seven design strategies, please see Part I and Part II for more tips!
5. Apply strain relief at transition areas from stiffener to flex.
- Stiffener material is common in flex circuit designs that have soldered components. While this rigid material is necessary for the soldered components, it can cause reliability issues during installation when the flex is bent at the stiffener location toward the stiffener.
- If the flex material will be bending toward the stiffener, it is highly recommended that an epoxy bead of Ecobond 45 be applied.
6. Ensure vias are located at least .050” away from bend zones.
Fig. 1 - Examples of a flex circuit with a bend radius and a plated through-hole.
7. Always put a 3D representation of your bend to install configuration on your drawings.
- Many problems can be avoided by informing your flex circuit vendor what the final configuration is going to be once used, this enables them to evaluate for potential bend radius issues.
- Most flex circuit drawings are only 2D. By showing a picture of the final configuration you are encouraging the discussion regarding materials, discussion about minimum bend radius and letting the flex vendor raise any concerns before build.
Fig. 2 - Examples of a 3D drawing of a flex circuit.
Andy Shaughnessy, Design007 Magazine
This week we have quite a variety of articles for you. There has been so much electronics industry news coming out of Washington, D.C., that it can be hard to keep track of what’s going on. So, Editor Michelle Te compiled a handy-dandy reference guide to recent legislation news, including our exclusive coverage. We need to keep an eye on these senators and representatives. They’ve been talking about the importance of our industry for the past year, but this is an election year, after all. They’ve been known to say one thing and do another.
Nolan Johnson, I-Connect007
Can it be Friday already? Seems like I’ve just barely put away my Tuesday dishes. Some weeks, I wonder where my days went as they fly by so fast I hardly even realize it. As I looked back through the news for the week, it was clear why everything went so fast: There was a lot going on. The news this week had a nice feel to it. It seems like the industry is starting to gain some traction again with shows, mergers and acquisitions, and companies getting to do those “extras” that they wanted to do before the pandemic reared its ugly head. It had a little of that “back to normal” feel, even if we aren’t quite there yet. What do you think? Are we normal yet?
Andy Shaughnessy, Design007 Magazine
I’m getting a lot of out-of-office replies. Are you all on the beach now? It’s 91 degrees every day here in Atlanta lately, but each afternoon it rains like we’re in a horror movie, and that drops the temperature down to the subtropical arena. Still, I’ll take heat over freezing any day. Things are heating up in our industry too, as we see from my top five choices this week. First-quarter electronic design revenue is up year-on-year, but PCB revenue barely moved the needle YOY. Editor Nolan Johnson spent the week at SEMICON West and the FLEX Conference, and he brings us a review of these conferences, co-located at the Moscone Center in San Francisco. As he notes, printed electronic circuits are beginning to gain a foothold in the market.