Speaking dice,
you are two top experts on the stage, I take the opportunity to ask you about this one: do you practice the analysis way by backetching the chips and study them from 'underside'? What acidous process is best for GaAs resp. Si?
Ingemar Hernefjord
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Creswick, Steven
Sent: den 19 augusti 2004 18:19
To: [log in to unmask]
Subject: Re: [TN] Picking Die
Joyce,
My suggestion for use of hotplate to determine presence/or not, of adhesive was considered to be a destructive test. In no way would I do this as a 100% 'fix'
Any die tested in this manner would be considered as scrap
Steve
-----Original Message-----
From: Joyce Koo [mailto:[log in to unmask]]
Sent: Thursday, August 19, 2004 9:20 AM
To: TechNet E-Mail Forum; Creswick, Steven
Subject: RE: [TN] Picking Die
depend on type of chip... adhesive residue may cause high electrical
resistance if the back is used as ground. cook on the heat plate must be a
short time... otherwise, you may cause some degradation of wirebondability
(depend upon how clean is your hot plate... you can varify cleanliness of
your chip surface before and after hot plate using DI contact angle
measurement, you will see the difference)...If I were you, I'll check all
the vacuum pick, process parameter, etc. If everything is OK as per
qualification, you still got stuck die, I'll reject the lot for sure...(not
that make me popular...)
-my cold 1.52 cents..
jk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Creswick, Steven
Sent: Thursday, August 19, 2004 6:35 AM
To: [log in to unmask]
Subject: Re: [TN] Picking Die
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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