I was waiting for someone else to answer this, but no one has, so I'll start
us off. Mechanical joining is definitely not my thing so this response is
more theoretical background, as it is somewhat tempered (groan) by lack of
practical knowledge. 

The lead frames for Multi-leaded components are made from iron alloys or
copper.
Originally they were punched from ribbons of iron based alloys with trade
names like Kovar and Fernico. There are various grades but they are
combinations of Fe/Ni/Co to match TCE. 42 alloy is Fe/Ni to save on the cost
of Co. TCE match is less than perfect, but good enough. 42 is the most
widely used alloy now. Copper is used more in high power devices.
 
Iron alloys can be tempered. Strictly speaking copper can not, but it can be
work hardened. So copper strip is cold rolled to differing degrees of
hardness. In power devices the 'frame is usually quite thick so I doubt you
would want to clinch it.
I think this means check the part specification for lead frame material, but
you can probably make a starter rule of thumb on clinching power versus non
power devices.

Regards 
 
Mike 


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kerr, Bryan (UK)
Sent: Tuesday, January 28, 2014 12:07 PM
To: [log in to unmask]
Subject: [TN] Tempered leads

Hi All

IPC spec's have requirements on clinching and cutting of "tempered leads".
Can anyone advise me of the typical components which would have such leads ?
Also, would these always be iron based alloys ?

Regards


Bryan Kerr
Principal Quality Engineer
CMA Lab and Process Engineering
BAE Systems Maritime Services
Manufacturing Hillend
Hillend Industrial Estate
Hillend
Nr Dunfermline
Fife
Scotland
KY11 9HQ
01383-836097

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