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|Thermal Characteristics for LSI Embedding Build-up PWBs|
|Keywords: thermal, characteristic, embed|
|Device-embedding technologies have come to the front with the marketfs request to enhance the electrical performance and to multiply functions of electronic modules. On the other hand, device-embedding technologies are accompanied by heat issues because heat density rises due to the dense arrangement of active devices in a given area. The one solution is to form continuous thermal conductive paths with copper and buried via interconnections from the embedded device to the surface of the PWB. Thus, it is very important to recognize the thermal properties of PWB components and to have creative plans on heat transfer at the PWB design. The authors have been developing LSI-embedding B2itTM (Buried Bump Interconnection Technology) PWBs, called e-B2it (Embedded B2it) PWBs, for advancing the miniaturization of electronic modules. The characteristic of e-B2it PWBs is the interconnection Vias made of Ag paste as the substitution for copper; consequently, the thermal feature of the Ag-paste bumps is an important factor for the thermal design of e-B2it PWBs. At the first, the authors investigate thermal conductivities of e-B2it PWB components; the Ag-paste bumps particularly, the insulation material and copper additionally. The equivalent thermal conductivity of e-B2it PWBs is measured experimentally; then, the thermal conductivity of each component is estimated on Computed Fluid Dynamics (CFD) analysis. Furthermore, the authors clarify how the abundance ratio of the insulation material and Ag paste affects equivalent thermal conductivity. The focus in the second stage is the enhancement of the thermal performance of e-B2it PWBs. The authors examine the effect of heat-spreading sheet on the surface of or inside the e-B2it PWBs on CFD simulation, exploring the depth, thickness and material of heat-spreader, and the contact between the heat-spreader and the embedded LSI. The improvement in thermal conductivity of the insulation material in e-B2it PWBs is also the discussing factors. Finally, the authors conclude with the effective heat spreading for e-B2it PWBs, and then expanding the total power dissipation of embedded LSIs. MOVED FROM EMBEDDED & INTEGRATED PASSIVES PER RAJEN CHANCHANI 5-1-09.|
Dai Nippon Printing Co., Ltd.
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