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| Date: | Mon, 10 May 2010 22:14:14 -0400 |
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LEDs are darn sensitive this way. Pb free is pretty nasty on the buggers. Also note that the power dissipation capability really nosedives at higher temperatures for the medium to high output parts: Its easy to blow them up by bad circuit design (ignoring the ambient temperature for the dissipation).
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Monday, May 10, 2010 10:08 PM
To: [log in to unmask]
Subject: Re: [TN] LED wiring bonding
Hi Chris,
Make sure its the wire bond and not the bonding wire that failed; in my experience it is the wires that are more susceptible.
Depending on the thermal excursion and the geometry, you can get both overstress and fatigue failures. The ductility of the Al-bonding wires is pretty low.
The FA is a great big 'IT DEPENDS'.
Werner
-----Original Message-----
From: Chris Mahanna <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, May 10, 2010 5:48 pm
Subject: [TN] LED wiring bonding
It's all LEDs these days!
We have an FA that shows poor wire bonds to GaAlAs/GaAs in microsection after
assembly. The failure is seen in the parts per hundred across different lots
and slightly different part numbers of LEDs.
The assumption would be that LED wiring bonding defects are very rare. Is
there something particular about these? Or is it the crimping and/or Pb-free
assembly that is pulling them apart?
The ones that seem more susceptible are GaAlAs Double Heteros.
Thanks.
Chris
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