Ed Holton wrote:
> Some help please!!
>
> I have recently become involved in a program that has to meet a
> temperature
> cycling criteria of -40C to +140C, 30 minute dwell times, 10sec
> transition
> time, for 1000 cycles. We have already made some units, and they are
> failing at various points in the temp. cycling. The failure mechanism
>
> appears to be the solder joint itself, however, there are some joints
> that
> are so strong we break the components, while others pop right off.
> The
> unit is being developed by another firm for us. There is discussion
> as to
> wether the problem is solder related or process related (cleanliness,
> etc.)
>
> The unit thus far is a ceramic substrate, silver palladium pads. The
> components are commercial grade resistors, capacitora and SOIC's. One
>
> problem appears to be the reflow temperature. With some of the high
> temp
> solders, the reflow temperatures are exceeding the component max.
> temperatures (ex. 250C for 30 seconds). Higher temp components may be
> the
> solution, but this is an automotive application, and cost is a big
> factor.
>
> Questions:
> What type of high temp solder is best for us, tin based, lead based,
> or
> gold based?
>
> Where can I find published papers?
>
> Component/terminal plating suggestions?
>
> Who are the experts in this field ( I have searched various archives
> to no
> avail)
>
> Is there a conference on high temperature soldering/applications
> coming up?
>
> What do you think about not soldering at all, instead glue all
> components
> to the board and attach to the substrate with wire bonding and
> encapsulate
> the whole thing(chip and wire)?
>
> Are there any conductive epoxies that might be used to replace the
> solder?
>
> Thanks for your help
>
> Ed Holton
> Hella Electronics
> 734-414-0944
>
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Hi,TechNetters!
I am also interested in answers for Ed's question.
Also, I would like to know if lead finishing could not be the culprit.
I had recently a failure case during vibration test and the component
which failed the test
had leads coated with 1-2 um 90/10 solder.
So, please address the answers to me too.
Thank you ,
Gaby
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