Issue link: https://iconnect007.uberflip.com/i/972396
22 FLEX007 MAGAZINE I APRIL 2018 which includes resin content. If there is an area that is low(er) in resin content, you might not fill adequately, causing resin starvation and ultimately shorts. There are times when we do build boards with a single sheet of prepreg (with half-ounce copper or less), but there is always a risk of inadequate flow, which will allow air entrapment, and ultimately shorted circuits. A simple, straightforward 8-layer rigid-flex will have 10 sheets of no-flow prepreg. Eight sheets are used to bond the package, and two sheets are used to mate up to the coverlayer to create a cut back coverlayer design for high reliability packaging (Figure 2). Now, 10 sheets of prepreg at three square feet each, and $2 per square foot is $60. The equiv- Figure 2: An 8-layer rigid-flex circuit.