Flex-rigid wiring board

Abstract

In a flex-rigid wiring board in which a rigid substrate formed from a rigid base material and a flexible substrate formed from a flexible base material are stack-joined and electrically connected to each other, the flexible substrate including a conductive layer having interconnecting electrode pads provided on at least one surface thereof, and the rigid substrate including a conductive layer having interconnecting electrode pads provided on at least one surface thereof in a position opposite to the interconnecting electrode pads on the rigid substrate, are locally connected electrically to each other with an anisotropic conductive adhesive layer interposed between conductive layers of substrate portions each including at least the interconnecting electrode pads. In this flex-rigid wiring board, transmission of high-frequency signals can be prevented from being delayed, noises can be suppressed, and an excellent electrical connection and connection reliability be assured.

1 . A method of producing a flex-rigid wiring board in which a rigid substrate formed from a stack of rigid base materials and a flexible substrate formed from a flexible base material are joined to each other, the method comprising the steps of: 
 preparing a flexible substrate including a plurality of first interconnecting pads and a plurality of first conductor layers connected to the first interconnecting pads, respectively;    preparing a first rigid-substrate layer having a cut formed at either end thereof while preparing a second rigid-substrate layer including a frame pattern exposed from the cuts, a plurality of second interconnecting pads formed in an area surrounded by the frame pattern, a plurality of via-contacts formed beneath the second interconnecting pads, respectively, and a second conductor layer connected to each of the via-contacts;    stacking the first and second rigid-substrate layers together to form a rigid substrate;    forming a coverlay between the first conductor layers of the flexible substrate and frame pattern of the second rigid-substrate layer to electrically insulate the frame pattern from the first conductor layers;    forming an anisotropic conductive adhesive layer between the first interconnecting pads of the flexible substrate and second interconnecting pads of the rigid substrate; and    fitting the free end of the flexible substrate into the cut in the rigid substrate to provide a compression connection between the first and second interconnecting pads via the anisotropic conductive adhesive layer.