--- title: The Use of Strain Relief with Rigid-Flex Printed Circuit Boards description: With rigid-flex circuit boards the transition from rigid to flex material requires a strain relief epoxy in the transition zone to protect underlying laminate. image: https://blog.epectec.com/hubfs/Blog/rigid-flex-circuit-board-transition-zone-from-rigid-to-flex-material.jpg --- [![Epec Engineered Technologies](https://www.epectec.com/images/logo.png "Epec Engineered Technologies")](https://www.epectec.com/) [![Epec Engineered Technologies](https://www.epectec.com/images/logo.png "Epec Engineered Technologies")](https://www.epectec.com/) - [Articles](https://www.epectec.com/articles/) - [Blog](https://blog.epectec.com/) - [Webinars](https://www.epectec.com/webinar/) - [Videos](https://www.epectec.com/videos/) - [Case Studies](https://www.epectec.com/case-studies/) - [News & Events](https://www.epectec.com/news/) - [Customer Portal](https://system.netsuite.com/c.406760/site/NSlogin.html) - [About](https://www.epectec.com/about/overview/) - 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[Login](https://secure.epecpcb.com/epec/) - [Register](https://secure.epecpcb.com/epec/index2.jsp) - [Home](https://www.epectec.com/) - [Blog](https://blog.epectec.com/) - The Use of Strain Relief with Rigid-Flex Printed Circuit Boards Share This Page: [LinkedIn](https://blog.epectec.com/#linkedin) [X](https://blog.epectec.com/#x) [Facebook](https://blog.epectec.com/#facebook) [Email](https://blog.epectec.com/#email) # The Use of Strain Relief with Rigid-Flex Printed Circuit Boards [![Chris Perry](https://blog.epectec.com/hubfs/Blog-Authors/chris-perry.jpg "Chris Perry")](https://blog.epectec.com/author/chris-perry) Written by [Chris Perry](https://blog.epectec.com/author/chris-perry) Posted on November 12, 2014 at 10:13 AM ![Chris Perry](https://blog.epectec.com/hubfs/Blog-Authors/chris-perry.jpg "Chris Perry") - [Tweet](https://twitter.com/share) For [rigid-flex printed circuit boards](https://www.epectec.com/flex/) (PCBs), the space joining rigid material to flex material (Transition Zone) sometimes contains imperfections that, although acceptable, could impact effectiveness of the final part. Transition zone imperfections can include any of the following: - Adhesive squeeze-out - Protruding dielectric materials - Crazing - Haloing If the parts are flexed at the interface, the remaining cured resin could damage the underlying flexible laminate. To protect the underlying flexible laminate, [flex PCB designers](https://www.epectec.com/flex/design/) require a strain relief epoxy in the flex transition zone. The applied, cured epoxy will help to extend the bending area past the remaining cured resin, as shown in the illustration below. ![Rigid-flex circuit board transition zone from rigid to flex material](https://blog.epectec.com/hs-fs/hubfs/Blog/rigid-flex-circuit-board-transition-zone-from-rigid-to-flex-material.jpg?width=650&height=325&name=rigid-flex-circuit-board-transition-zone-from-rigid-to-flex-material.jpg) *Rigid-flex circuit board transition zone from rigid to flex material.* This strain relief epoxy can be controlled to be either rigid or flexible, depending on the requirements of the final product. It is important to note that when designing strain relief into your rigid-flex PCB design that you refer to IPC-2223, section 5.2.9 for complete guidelines and limitations. [![Free Ebook Download: Top 6 Quality Issues Seen in Flex & Rigid-Flex PCBs](https://no-cache.hubspot.com/cta/default/707152/f1da5027-aae4-46b7-ba59-65371917f1da.png)](https://cta-redirect.hubspot.com/cta/redirect/707152/f1da5027-aae4-46b7-ba59-65371917f1da) ## Summary The transition zone is a very sensitive area of printed circuit boards that must be constructed with great care. Even the slightest miscalculations will result in errors that impact the performance of your PCB. Here at Epec, we take the time to be certain our rigid-flex PCBs meet the high standards our customers need for their products. If you have any [questions or concerns with your rigid-flex board](https://www.epectec.com/flex/info-request.html), we'd love to hear from you! Feel free to reach out to us during the design stage, our engineers are always ready to help. --- ## Key Takeaways - **Transition zones in rigid-flex PCBs are sensitive areas:** Imperfections such as adhesive squeeze-out, protruding dielectric, crazing, or haloing can occur and impact performance. - **Strain relief epoxy protects the flexible laminate:** By extending the bend area past cured resin, epoxy prevents damage when the board is flexed at the rigid-to-flex interface. - **Epoxy can be tailored to requirements:** Strain relief material can be either rigid or flexible depending on the final product’s needs. - **Design guidelines exist in IPC-2223:** Section 5.2.9 provides detailed rules and limitations for properly applying strain relief in rigid-flex designs. - **Precision in the transition zone is critical:** Even minor errors during construction can compromise PCB performance, making careful design and manufacturing essential. - [Tweet](https://twitter.com/share) Topics: [Quality Solutions](https://blog.epectec.com/topic/quality-solutions), [Flex & Rigid-Flex PCB's](https://blog.epectec.com/topic/flex-rigid-flex-pcbs) --- [Next](https://blog.epectec.com/becoming-a-hybrid-supplier-in-the-electronics-industry) | [All posts](https://blog.epectec.com/all) | [Previous](https://blog.epectec.com/how-to-select-your-battery-pack-cell-type) [![New Call-to-action](https://no-cache.hubspot.com/cta/default/707152/846c020a-b0a4-42f3-974e-1b694b491d92.png)](https://cta-redirect.hubspot.com/cta/redirect/707152/846c020a-b0a4-42f3-974e-1b694b491d92) ## Leave a Comment --- ## Related Posts --- ### Recent Posts --- ### Posts by Topic - [Printed Circuit Boards (157)](https://blog.epectec.com/topic/printed-circuit-boards) - [Product Design (132)](https://blog.epectec.com/topic/product-design) - [Battery Packs (118)](https://blog.epectec.com/topic/battery-packs) - [Cable Assemblies (99)](https://blog.epectec.com/topic/cable-assemblies) - [Flex & Rigid-Flex PCB's (92)](https://blog.epectec.com/topic/flex-rigid-flex-pcbs) - [Electronics Industry (61)](https://blog.epectec.com/topic/electronics-industry) - [User Interfaces (54)](https://blog.epectec.com/topic/user-interfaces) - [Quality Solutions (32)](https://blog.epectec.com/topic/quality-solutions) - [Flexible Heaters (30)](https://blog.epectec.com/topic/flexible-heaters) - [Events, Training, and Support (9)](https://blog.epectec.com/topic/events-training-and-support) - [RF Products (7)](https://blog.epectec.com/topic/rf-products) - [CNC Machining (3)](https://blog.epectec.com/topic/cnc-machining) - [Fans & Motors (1)](https://blog.epectec.com/topic/fans-motors) See All --- --- ### Need Help with A Project? 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