Subject: Re: Bond wires

From: "Ravender Goyal" <[email-masked]>
Date: 9 Mar 1994 10:30:30 -0800

Reply to:   RE>Bond wires
Again, having faced this problem in extreme situations such as RF/ telecom
circuit designs, there are closed form rules of thumb available that can
be used for bondwire modeling- both for wedge bonding as well as ball
bonding, with and without ground planes. These have worked well with me
upto 10- 12 GHz in the past. Such formulae are a function of distance
between bonding pads (Manhattan length), type of bonding techniques- wedge
or ball (determines the curvature in the bondwire path), distance from
ground plane (or no- ground plane), number of bondwires on a pad
(detemines the effective bondwire inductance- such as if you keep
increasing the number of bondwires in parallel believing it will be
decreasing the inductance, it is not true after second or third bondwire
there is minimal reduction in inductance), bondwire diameter, bondwire
material, etc. The other option is to use 3D field solvers to analyze bond
wires and provide the L and C matrices.

Ravender
--------------------------------------
Date: 3/8/94 6:50 PM
To: Ravender Goyal
From: Bob Ward
From: [email-masked] (Bob Ward)
To: [email-masked]
Subject: Bond wires
Date: Tue, 8 Mar 94 20:37:50 CST

All -

Kumar makes a _very_ good point about bond wires.  I have found them to be
a real
bugaboo in making leadframe models.  They are not at a uniform height
above a
ground plane, even though they have relative well behaved cross sections. 
But
how do they _really_ behave?  Even more puzzleing to me is how to treat
the case
of parallel bond wires where on power or ground connections, for instance,
we 
may have two, three, or even more bond wires in parallel between the
leadframe
lead and the bond pad.  I imagine the mutual C is pretty well shorted out
( or
is it? ) but that the mutual L exists and is pretty well still active ( or
is
it :-) )KK? :-) ).  I agree this may a good are for some university
research.  Comments?

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