| 摘要 |
The number of LIMMS devices in an assembly is increased by stacking multiple layers of LIMMS devices on top of one another, and interconnecting those device layers at an array of solder pads using solder balls. Each device layer uses vias to bring the needed conductors to the array of solder pads. All signals for the entire multi-layer assembly can be routed through the bottom LIMMS device layer to pass, through another array of solder pads onto a "mother substrate" of ceramic or other material that carries the multi-layer assembly. Alternatively, signals may enter or leave the upper LIMMS device layer by way of a flexible printed circuit harness. Vias may pass, either directly or by "dog legs" on interior surfaces, completely through the bottom LIMMS device layer, and through other device layers as needed. Opposing vias formed in the pair of substrates in a device layer have interior non-contacting pads that are bridged by a small ball of liquid metal held in place by a hole in a dielectric layer. Using patterned layers of dielectric to form bridging holes, cavities, channels and interconnecting passages for the LIMMS devices of both layers facilitates these needed vias and traces. Suitable thick film dielectric materials that may be deposited as a paste and subsequently cured include the KQ 150 and KQ 115 thick film dielectrics from Heraeus and the 4141A/D thick film compositions from DuPont.
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