Application considerations for plated-through-hole flexible circulatory

The need for a reliable, economical joining technique for electrical interconnections in telephone packaging has initiated several studies at BTL. Two such studies have involved the application of plated-through-hole flexible printed circuits to the Touchtone Trimline Handset and the 584 Panel, part of the 1A2 Keyset System. As these studies have progressed, the feasibility of applying plated-through-hole flexible circuitry to other Bell System equipment has become more obvious. For the convenience of those contemplating the future use of such an approach, this paper puts forth the experience thus far gained in the above two studies. Included are circuit design layout considerations, several mass bonding techniques for electrical interconnections and some basic data on flexible substrate materials.