--- title: Flexible Circuit Boards Connector Options, Which One Is Best For You? description: Learn how ZIF, header, crimp, and interposer connectors compare for flexible circuit boards, and which option best fits your design requirements. image: https://blog.epectec.com/hubfs/blog/male-female-connector-on-flexible-pcb.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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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) # Flexible Circuit Boards Connector Options, Which One Is Best For You? [![Paul Tome](https://blog.epectec.com/hubfs/Blog-Authors/paul-tome.jpg "Paul Tome")](https://blog.epectec.com/author/paul-tome) Written by [Paul Tome](https://blog.epectec.com/author/paul-tome) Posted on September 1, 2021 at 10:24 AM ![Paul Tome](https://blog.epectec.com/hubfs/Blog-Authors/paul-tome.jpg "Paul Tome") - [Tweet](https://twitter.com/share) [Flexible circuits](https://www.epectec.com/flex/) support a wide range of interconnect options, including nearly all connector systems commonly used on [rigid printed circuit boards](https://www.epectec.com/pcb/) as well as several solutions developed specifically for flexible circuit applications. Selecting the most appropriate connector requires balancing multiple design requirements, including interconnect count, available board space, signal integrity, current-carrying capability, retention requirements, assembly considerations, and environmental demands. No single connector system is optimal for every application, which is why connector selection should be evaluated early in the design process. [![Free Download: Top 6 Flexible Circuit Board Design Checks](https://no-cache.hubspot.com/cta/default/707152/d155352b-d452-4450-8a92-07020e10d9a6.png)](https://cta-redirect.hubspot.com/cta/redirect/707152/d155352b-d452-4450-8a92-07020e10d9a6) ## What Drives Connector Selection in a Flex Circuit Design? The connector chosen for a flexible circuit must support both the electrical and mechanical requirements of the final assembly. **Important selection factors include:** - Number of signals or interconnect points - Available space on the mating rigid PCB - Signal integrity requirements - Current-carrying requirements - Mechanical retention requirements - Assembly and serviceability considerations The relative importance of these requirements often determines which connector family provides the best solution. ## Why ZIF Connectors Are the Most Common Flex Circuit Interconnect [Zero Insertion Force (ZIF) connectors](https://www.epectec.com/flex/termination-methods.html) are the most widely used method of connecting a flexible circuit to a rigid PCB or to another flex circuit. The ZIF connector was specifically developed to take advantage of flex circuit capabilities and can support applications ranging from low-level signal routing to controlled impedance designs and higher-current applications. ![Flexible circuit with ZIF connectors](https://blog.epectec.com/hs-fs/hubfs/blog/flexible-circuit-with-zif-connectors.jpg?width=800&name=flexible-circuit-with-zif-connectors.jpg) *Flexible circuit with ZIF connectors.* A ZIF connection functions as a one-part connector system. The connector itself serves as the female interface and is soldered to the rigid PCB. The flex circuit becomes the mating male interface through its contact fingers, eliminating the need for an additional connector mounted to the flex circuit. **This approach provides several advantages:** - Lower system cost because only one connector is purchased and assembled - Reduced interconnect points and solder joints - High-density interconnect capability - Small form-factor solutions with multiple contact pitch options - Availability of higher-retention connector designs - Compatibility with [controlled impedance applications](https://blog.epectec.com/flex-rigid-flex-pcbs-mastering-controlled-and-impedance-signals) and elevated current requirements ## Designing a Flex Circuit for a ZIF Connector Successful ZIF integration depends on compliance with the connector manufacturer's specifications. **Critical design elements typically include:** - Contact finger dimensions - Contact finger spacing relative to the flex outline - Contact area dimensions - Supporting stiffener dimensions We recommend including the specific ZIF connector part number on the fabrication drawing so that connector compatibility can be verified during design review. Errors in any of these areas can negatively affect connector performance and reliability. ## How Modern ZIF Designs Improved Reliability Early ZIF connector systems commonly relied on wedge-style retention mechanisms. In these designs, a movable wedge compressed the flex circuit within the connector to create both electrical contact force and mechanical retention. Assembly required opening the wedge, inserting the flex to the proper depth, and re-engaging the wedge mechanism. **Potential reliability issues could occur if:** - The flex was not fully inserted - The wedge lock was not completely closed - Excess force pulled the flex partially out of the connector More recent ZIF designs addressed these concerns through hinged locking lids and retention tabs incorporated into the flex outline. With this approach, the flex is positioned within the connector and secured when the lid is closed. The retention tabs mechanically engage the connector, substantially increasing pull-out resistance. These designs have enabled the use of ZIF systems in high-reliability applications. Higher current requirements are commonly addressed by using multiple contacts. A common maximum current rating cited for a ZIF contact is 500 mA per contact. ## When Standard Male/Female Header Connectors Are the Better Choice Flexible circuits can accommodate many of the same SMT and PTH connector systems used on rigid PCBs. To support these connectors, the flex circuit incorporates a [localized stiffener](https://www.epectec.com/flex/flex-circuit-stiffeners.html), typically FR4, beneath the connector area. The stiffener provides mechanical support that flexible materials alone cannot deliver. ![Male/female connector on a flexible PCB.](https://blog.epectec.com/hs-fs/hubfs/blog/male-female-connector-on-flexible-pcb.jpg?width=800&name=male-female-connector-on-flexible-pcb.jpg) *Male/female connector on a flexible PCB.* For SMT connectors, the stiffener is bonded to the opposite side of the flex in the connector region to create a stable mounting surface. For PTH connectors, the stiffener is attached to the connector insertion side and includes clearance holes that allow connector pins to pass through and engage the flex circuitry before soldering. Standard FR4 stiffeners are available in a wide range of thicknesses, from approximately 0.010" to 0.059". Where additional support is required but available space is limited, thinner stainless-steel stiffeners can be utilized. ### Advantages of Male/Female Connector Systems These solutions are often preferred when a design requires: - More than 40 signals - Current levels greater than approximately 3 to 4 amps - Screw-lock retention systems - High shock and vibration resistance - Compatibility with existing hardware platforms - Custom connector configurations combining power and signal requirements ## Crimp Contacts for Flex-to-Wire Harness Connections Crimp contact systems are derived from traditional wire harness connector technology and provide a direct connection method between flexible circuits and [wire harness assemblies](https://www.epectec.com/cable-assemblies/wire-harnesses.html). In this approach, contacts are mechanically crimped through designated flex circuit contact areas. A connector housing is then installed over the contacts, creating a pluggable interface with the mating wire harness connector. Although less common in many modern designs, this approach offers several benefits. ### Advantages of Crimp Contact Systems - Automated simultaneous contact crimping - Familiar wire harness assembly methods - Elimination of a separate interface board between the flex circuit and wire harness - Reduced interconnect complexity in certain applications ## Interposer Connectors for Very High Pin Counts Interposer systems serve a specialized role in applications with exceptionally large numbers of interconnections. These systems are commonly used when pin counts reach 300 contacts or more. An interposer is positioned between the flex circuit and the rigid PCB. Mechanical clamping plates apply compression across the interposer and maintain consistent contact force throughout the connection area. Although these systems can be comparatively expensive, they provide capabilities that are difficult to achieve using traditional connector technologies. ### Advantages of Interposer Connectors - Support for extremely high pin counts - Solderless mechanical connection - Simplified assembly through compression-based attachment - Positive mechanical retention suitable for shock and vibration environments - Custom connection geometries and contact configurations ## Matching the Connector to the Application ZIF connectors remain the most common and cost-effective connector solution for many flexible circuit designs because they provide a favorable combination of density, reliability, assembly efficiency, and electrical performance. However, no single connector family satisfies every design requirement. Applications with higher current demands, extreme environmental conditions, large interconnect counts, existing hardware constraints, or direct wire harness integration may be better served by alternative connector technologies. The most successful connector selections are made by evaluating the complete electrical, mechanical, assembly, and reliability requirements of the final product rather than focusing on connector type alone. ## Summary ZIF connectors are by far the most commonly used and most cost-effective method of connecting a flex circuit to a rigid PCB or another flex circuit throughout all segments of the electronics industry. While ZIFs do meet a very wide variety of requirements, they cannot meet all interconnect needs. Flex circuit technology allows for any type of connector system to be used to meet a design’s specific/unique requirements. --- ## Key Takeaways - **Flexible circuits can use nearly any connector system**, from ZIF connectors to male/female headers, interposers, and crimp contacts, depending on the design needs. - **ZIF connectors are the most popular choice** for flex circuits, offering cost efficiency, high density, and reliable connections with simplified assembly. - **Male/female header systems are ideal for high-current or high-pin-count applications**, providing robust retention and compatibility with existing rigid PCB designs. - **Interposer connectors excel in very high pin count applications**, offering solderless, mechanically clamped connections that improve reliability in shock and vibration environments. - **Connector selection depends on multiple factors**, including interconnect count, available space, current requirements, and retention needs, making early design planning critical for successful integration. - [Tweet](https://twitter.com/share) Topics: [Flex & Rigid-Flex PCB's](https://blog.epectec.com/topic/flex-rigid-flex-pcbs) --- [Next](https://blog.epectec.com/what-does-it-mean-to-constrain-a-solidworks-sketch) | [All posts](https://blog.epectec.com/all) | [Previous](https://blog.epectec.com/pcb-data-sets-what-you-need-to-know) [![New Call-to-action](https://no-cache.hubspot.com/cta/default/707152/9262fae5-131d-4836-8290-f9ef3d12f88c.png)](https://cta-redirect.hubspot.com/cta/redirect/707152/9262fae5-131d-4836-8290-f9ef3d12f88c) ## Leave a Comment --- ## Related Posts --- ### Recent Posts --- ### Posts by Topic - [Printed Circuit Boards (161)](https://blog.epectec.com/topic/printed-circuit-boards) - [Product Design (138)](https://blog.epectec.com/topic/product-design) - [Battery Packs (121)](https://blog.epectec.com/topic/battery-packs) - [Cable Assemblies (102)](https://blog.epectec.com/topic/cable-assemblies) - [Flex & Rigid-Flex PCB's (95)](https://blog.epectec.com/topic/flex-rigid-flex-pcbs) - [Electronics Industry (61)](https://blog.epectec.com/topic/electronics-industry) - [User Interfaces (55)](https://blog.epectec.com/topic/user-interfaces) - [Quality Solutions (33)](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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