3. An IC chip is soldered onto a printed wiring board (PWB) and then subjected to underfilling. Assuming that a first-or

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3 An Ic Chip Is Soldered Onto A Printed Wiring Board Pwb And Then Subjected To Underfilling Assuming That A First Or 1 (48.14 KiB) Viewed 36 times

3. An IC chip is soldered onto a printed wiring board (PWB) and then subjected to underfilling. Assuming that a first-order Newtonian fluid flow is always occurring, calculate the underfill time in two possible cases, namely if: (a) Capillary underfill is used. Assume that the standoff gap height h between chip and substrate is 250 um and that the chip is square, with a size L = 5 mm. The underfill fluid has the surface tension o= 20 mN/m, the apparent viscosity u = 1.5 Pa-s and the wetting angle a=30°. (b) Injection underfill is employed instead. In this case the injection pressure Pris 1.01 times larger than the atmospheric pressure Pa = 101,325 N/m². What can you comment regarding the difference between the results in the two cases and which would be more advisable in what circumstances?