[SI-LIST] FW: Re: currnet through wire bond
- From: <jeff.latourrette@xxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Thu, 16 Feb 2006 14:16:03 -0700
Kami:
You will also find variation in the length of wire and size of pad it =
connects to, as the spreading of heat helps shorter, heat-sunk wires =
carry a little more current before fusing. =20
Not surprisingly, wires usually fuse near the middle where it gets hot =
the fastest. What's under the pad also makes a difference, especially =
if it's running at elevated temperatures. Benefits of any heat-sinking =
would depend on the speed at which heat can be drawn out of the wire vs =
how fast you push current through the wire. This may be important in =
pulsed vs continuous operation.
Wires inside a package (with or without insulating overmold compound) vs =
in air will make current capacity lower.
With access to thermal imaging, which is typically used to measure die =
temperatures you can also "see" just how hot your wires are getting and =
whether you are anywhere close to fusing temperatures.
Found a source, "Reference Data for Radio Engineers", which does have an =
equation for fusing current: I=3DK*d^(3/2), where d is wire diameter =
(inches) & K is a material constant in their table. Of course they =
don't even list K for Gold in my older edition, but for Aluminum, =
K=3D7585, & for Copper K=3D10244 (Pure Gold's melting point is just 20 =
deg below Pure Copper's). Calculated values in their table also stopped =
at 40 Gauge (d=3D3.1 mil). They wisely warn you that due to factors =
(like above), this should only be used for an approximation.
Using this approximate equation, I get:
0.324A for 1mil Cu (which is probably very close for Au)=20
0.240A for 1mil Al
These seem very conservative compared to postings so far.
Hope this helps,
Jeff LaT.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of Javier DeLaCruz
Sent: Wednesday, February 15, 2006 2:41 PM
To: azizi_kamran@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: currnet through wire bond
Kami,
Typically the gold wire used at the major subcons tend to be similar. =
=3D
The fusing current of the wire may vary depending upon how the wedge =3D
side was tailed off, so be careful with this if the wedge side is =3D
over-bonded. I am also assuming you are using ball bonds (not wedge nor =
=3D
ribbon bonds.) Data that I have shows following fusing current for =3D
wires at different diameters:
D (mils) I(A)
0.8 0.4
1.0 0.5
1.1 0.55
Regards,
Javier
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Kamran Azizi
Sent: Thursday, February 09, 2006 5:46 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] currnet through wire bond
Question: what is the current handling of wire bonds? any equations for =
=3D
that. What is the maximum current a wire bond can tolerate?
=3D20
thank you
Kami
=3D20
=3D09
---------------------------------
=3D20
What are the most popular cars? Find out at Yahoo! Autos=3D20
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