Svart

Re: Solder Paste Blues
« Reply #20 on: October 24, 2009, 12:30:20 PM »
you have to be careful with some chips these days.  Pay attention to their soldering heat curves.  i don't think 450F would hurt them but you never know how long they can stand it either.

We recently had a new PCB go into production and found strangeness with a high speed comparator.  Come to find out, it's soldering profile was being exceeded and the chips were being cooked..

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JohnRoberts

Re: Solder Paste Blues
« Reply #21 on: October 24, 2009, 12:41:41 PM »
I'll find out... I'm in the process of applying fire now.. so far it looks good... Of course once the processor comes up, I'll need to crank out some code before the other chips can be tested,,,

+1, I have had bad experience in the past with SMT film caps changing value and melting at a contract manufacturer I used... In this design there is nothing that temp sensitive as far as I can tell from the data sheets, which say no problemo with lead free temps...

So far these parts seem pretty robust, even the LEDs have survived me removing a couple to turn around...

I don't know how hot my 450' really was...   My research said 450' for 30 seconds, It took me several, couple minute hits to melt the paste so I suspect my PCB was not that hot...  The pan I had the pcb sitting in was probably acting like a local heat sink to level temperatures somewhat.

But thanks for the heads up...

JR


 
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