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4
The variability of COB thickness poses yet another design challenge for a socket product. COB substrates are available in
a variety of materials and thicknesses that need to be accommodated. The thinner and more brittle ceramic packages can
easily crack under pressure when used with flexible thermal interface pads and therefore consequentially commonly use
greases as TIMs. On the other hand, the more durable aluminum substrates commonly use grease or flexible TIM
materials. Any holder being considered by a manufacturer needs to be evaluated relative to how it accommodates these
varying stack heights posed by COB applications. One method is commercially available that utilizes a combination of
optional thermal springs and housing ledges to accommodate both types of COBs. An example using aluminum substrate
COB is shown in Fig. 13 below.
The same system when used with the thinner ceramic substrates is shown in Fig 14 with clearance to avoid exerting screw
pressure on the ceramic substrate .
Fig. 13
Fig. 14