Karen,
Bruce is correct in that the tape mastic should not be on the backside of the device IF properly ejected, however, sometimes that is a big "if". Many individuals feel that you have to poke THROUGH the tape in order to eject the device. I find that tends to transfer a small amount of adhesive, so I elect NOT to poke through the tape. It is all a game of tip diameter, needle travel, time, etc.
I have had similar experiences, but never to the magnitude that caused undo grief. On occassion, I have washed waffle packs out with clean IPA and this has helped. For those [empty] waffle packs that seem prone to die sticking [naturally, assuming the cavity size is large enough, etc], I just trash them.
I have a few devices which are essentially optically clear. If there is any mastic transfer during the die ejection process, it shows up as a small amber/brown dot after the die attach adhesive has been cured [can see it from the top]. I guess from a silver lining stand-point this allows me to verify just exactly where the ejection needle is contacting the device - but that is something I can generally do without :-)
I wonder .... if your device is large enough ... could you carefully remove it from the waffle pack with tweezers, flip it upside down on a 200-250°C heat stage for 10-15 minutes, char the mastic a bit [if it is there], then pull it off and look at it under the microscope. I am guessing that if mastic were there, it might show up if the lighting were just right.
I have had situations where the mastic is along the very edges of the device. Believe this was due to cutting too far into the nitto tape during dicing. Like Bruce said, this has been fixed with a better vacuum.
Just goes to show that even the little things are not so trivial.
Have a good day!
Steve Creswick - Gentex Corp
-----Original Message-----
From: Karen Walters [mailto:[log in to unmask]]
Sent: Wednesday, August 18, 2004 2:14 PM
To: [log in to unmask]
Subject: [TN] Picking Die
Has anyone ever experience die sticking to the waffle paks during die
attach. Please let me know what your solution was to this problem. We
believe it is Nitto tape residue that sticks to the back of the die when
the die are picked from the wafer ring to the waffle pak
Please let me know your experience with this.
(Embedded image moved to file: pic26500.pcx)
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