Issue link: https://iconnect007.uberflip.com/i/1108006
14 FLEX007 MAGAZINE I APRIL 2019 3. Beware of the Dual-row ZIF Connector Fine-pitch, dual-row zero insertion force (ZIF) connectors are becoming increasingly common because they greatly reduce the footprint area of an interconnection compared with single- row ZIF connectors (Figure 5). However, several inherent characteristics of dual-row ZIF fingers make them vulnerable to fracturing (Figure 6): • Pad-conductor transition: The transi- tion point where the pad narrows down to pass between adjacent pads is vulner- able to cracking • Brittle nickel underlayer: The stan- dard surface finish for ZIF contacts is electroless nickel immersion gold (ENIG), but nickel underplate is brittle, and cracks on this surface can translate through the copper underneath • Thin stiffeners: In the quest to min- iaturize, connector suppliers have responded by reducing the standoff height of the connector receptacle; therefore, the "stiffeners" on the oppo- site side of ZIF fingers are now so thin they act more like shims than stiffeners, offering little support The consequence of these factors is that any misalignment during insertion that causes the end to fold or deflect, even moderately, can crack the fingers. In some cases, cracks in the copper conductors can be small, resulting in partial or intermittent connections that may not be detected during electrical test—the worst case of a walking wounded. Because these are inherent characteristics of the ZIF contacts established by the ZIF con- Figure 5: ZIF connectors are a popular method to terminate FPCs for interconnection with other circuits. The traditional single-row style (L) is increasingly being supplanted by dual-row versions (R), which can greatly reduce the connector footprint. Figure 6: The design and construction of dual-row ZIF connectors makes them vulnerable to cracking.