bond wire length
bond wire length
(OP)
I've been told the maximum length to run a 0.001" Au bond wire is 0.065". Is this a standard telecom spec and if so where would I find details about how this spec was set?
Is this a spec for droop (potential shorting), strain (breakage during vibration), inductance, or something else?
Thanks,
John D
Is this a spec for droop (potential shorting), strain (breakage during vibration), inductance, or something else?
Thanks,
John D





RE: bond wire length
http
We consider the potting material if the bond is potted as well as the environment when calculating max length.
Harold
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RE: bond wire length
http
http://www.natelengr.com/documents/dg3wirebond.pdf
There are a number of reasons why one might limit the length, and you've mentioned most of them.
Some others:
> IR drop
> bonder limits -- You have move the bonder tip up and out to draw additional length, and then come back down. I can't really if there really a mechanical limit on bonders, though.
> damage to first bond -- drawing additional wire puts stress on the first bond
I vaguely recall seeing bonds longer than 0.1" but that was mainly due to putting a really small die in a package that was too large for it. And that was due to the fact that the large package was off-the-shelf, and the exercise was for a special test.
As to some of the concerns you raised:
> droop -- no necessarily a problem, since die are usually passivated, so shorting to the die is unlikely. Shorting to other bonds might occur if the loop height is excessive. Certainly, the longer the bond, the more sway space you should have allowed for in the bond pad layout.
> fatigue -- unclear, since the longer the bond, the smaller the angular deflection relative to the foot of the bond.
My guess would be that the most prevalent reason is inductance, particularly with high-speed, high-transient current devices. A poor bonding layout can result in several tenths of volts of bounce during a transient, enough to potentially change the logic state of the signal on the wire.
TTFN
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RE: bond wire length
The Natel link is interesting; I like that it gives a maximum length. I expect the clearance limits are tailored to their bonding equipment.
I'm thinking that fatigue may be an issue not due to the deflection angle, but due to the increased mass and thus the increased torque on the bond.
Thanks for the responses.
John D
RE: bond wire length
http:
While it doesn't explicitly cover bonding, it does discuss the bond wire characteristics out to 5mm (0.197").
RE: bond wire length
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: bond wire length
I seem to remember that some of the glob-top products had quite long bonds but it didn't really matter as it was encapsulated within minutes of bonding. Wasn't my line so can't be sure of lengths.
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