New Approach To Large Current Printed Circuit Boards(LC-PCB) With Attaching Bus-bars By Caulking Fasteners

We have developed a new type large current printed circuit board (LC-PCB). The LC-PCB consists of conventional PCB(FR-4) on which a bus-bar for large currents is mounted by caulking a fastener. The features of this LC-PCB are: (1) easier manufacturing, (2) three-dimensional wiring, and (3) large electric capacity. A compressive stress is constantly applied to the junction of the LC-PCB, where the fastener is caulked onto the PCB. To evaluate the long-term reliability of this junction, we performed an aging test at 378 K and a creep test using a test circuit board. Even after 2000 hours of agmg, the electrical resistance of the junction kept its initial value (as low as 0.15m.Q) and the mechanical sticking force of the fastener reduced by only 20% from its initial value. The degree of reduction of the mechanical sticking force of the fastener is far lower than the reduction estimated from the calculated creep value, because the creep and stress relaxation occur at the same time at the fastener caulking area. Thus, the LC-PCB exhibits a hiEh connection reliabihty, both electrically and mechanically, even after 2000 hours of aging at 378 K.