Issue link: https://iconnect007.uberflip.com/i/1503357
JULY 2023 I DESIGN007 MAGAZINE 63 would be super difficult. e tolerances were mils across inches of area. First, we had a call with the component pro- vider to understand the tolerances they could hold. Once we had agreement and thought the tolerances were doable, we manufactured a machined stainless-steel stiffener that held very tight tolerances. e stainless material provided not only the flatness required, but the strength to hold a five-layer flex flat. e stiffener was pressed onto the flex and the BGA component was placed using SMT. Inspection was done using X-ray to confirm all balls were seated. Success! Mechanical Support We use stiffener material on flex to assist with mechanical requirements of the design. While the use of flex does provide "flexibility" of the circuit, there may be a need to mount, bend, attach, or support the flex in an applica- tion. is could include connector mounting holes, strain relief for bend areas, connec- tor gripping for mating and unmating, any flex mounting requirements, or wire bonding Figure 4: Stainless stiffener for flatness. Figure 5: FR-4 stiffener mechanically supporting TNC connectors. Figure 6: Stiffener supporting display. Figure 7: Stiffeners supporting SMT connectors and wire bond area. support. e use of a stiffener depends on the outline and shape of the design. e material used in these applications tends to be FR-4 and polyimide. Figures 5–7 demonstrate a few applications where a stiffener is supporting the flex.