Victor,
	This may not make me the most popular person on TechNet, but as far as I know circuit designers don't know what thermal mass and temperature gradients are.
	As far as using the Taguchi method to develop profiles, that is a bit more involved then your run of the mill manufacturing engineer wants to get involved with.  They just don't have that kind of time.
	The up side is, convection ovens make profiling a lot easier than the older IR and convective IR ovens, and there are rules of thumb that can be applied to the development of a reflow profile.
	If you need any additional help with this, drop me a line or call me. 

John Guy
American Competitiveness Institute (EMPF)
317-655-3673 x130
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----------
From: 	Victor Li[SMTP:[log in to unmask]]
Sent: 	Tuesday, November 19, 1996 7:42 AM
To: 	[log in to unmask]; [log in to unmask]
Subject: 	Gen : SMT design/process issues



Two thoughts came to my mind concerning the complexity of PCB layout and 
the temperature relationships.

1) When circuit designers design the PCB layout, do they ever consider the 
thermal mass issues and try to layout the components in such a way that 
a more even temperature gradient would result across the PCB during reflow? 
e.g., trying to put larger components around the edge and smaller ones at 
the center region.

2) Does process engineer utilize the Taguchi method to find out the best 
oven temperature settings at different zones, in order to maintain an uniform 
temperature gradient across the PCB?  Or does the forced air furnace 
already taking care of this temperature problem?

Thank you very much in advance.

Vic

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