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Technology Stocks : Advanced Micro Devices - Moderated (AMD) -- Ignore unavailable to you. Want to Upgrade?

To: Bill Jackson who wrote (78145)	4/24/2002 10:48:12 AM
From: pgerassi	Read Replies (2) \| Respond to of 275872

Dear Bill: The bumps are part of the die and is part of why they call it flip chip technology (FCPGA). THe original orientation was circuits facing up and pads surrounding the die were connected with wires going from pads on the dies to pads on the substrate. With flip chip, the connections are made with bumps on the die being placed on pads on the substrate. This is exacting work due to the size of these bumps and the areas around them. You do not want high temperatures for this bond once the chip is placed because of the vert short paths to the active areas on the die. Then the package needs to be retested due to defects in the bonds or substrate. Only then would you cover it with a HIS. At this point only two connection methods exist that would not harm the working CPU, mechanical force with some filler between the die and the HIS to remove voids or some sort of adhesive that is thermally conductive. Placement is not as critical or precise as the die mount operation. Notice that either of these can just as easily be done aftermarket with a HSF which leaves the only advantage to a HIS being mechanically protecting the die. Notice during the wire bond days that the chip was soldered or bonded to the substrate and that could be copper or some other metal because of the loose tolerances allowed. Then HIS made sense because it was required. Pete