This is an excellent question, but our problem is slightly different.
Our production line uses a no-clean wave soldering process and in-line BON
testing. Using the continuous flow manufacturing philosophy, we test the
boards as soon as they are built(previously we used a batch process, with a
stand alone BON). Our problem is that the boards need to be cool,
basically room temperature, before they enter the BON, or else you will get
false resistor readings due to the high temperature. We presently have a
series of muffin fans after the wave and a length of conveyor to cool the
board before testing. We are still working to improve this, including
trying Dave Hillmans recommendation of fans blowing over the chilled water
pipes(we started this before his response--I was glad to see that great
minds think alike LOL). The secret with fan cooling is high air flow
volume with low force or pressure. This way you get the maximum cooling
effect while avoiding the ESD effect of high pressure air. However, to
cool a board down to room temperature in a short time period, you need to
blow air that is cooler than room temperature. The cooling curve is
asymtopic, it is the last 50-100 degrees that is the hardest!
I am experimenting with a vortex tube, blowing cold air on the product, but
this is extremely loud.
There is a conveyor company that markets an enclosed FIFO buffer tower with
an air conditioner, this is rather expensive, not something we are trying
right now.
I have recommend to many Equipment vendors(Electrovert, Seho, etc), that
they need to create a stand alone piece of equipment similar to what is
found in the cooling section of the newer reflow ovens today, i.e. a one
meter long cooling section that can be used to cool boards down after the
wave solder or any other operation. SEHO presently has one under
development..
If anyone has any other recommendations, I look forward to hearing them
QUESTION: not trying to be a smart alec, but in the original question, the
problem is taking ltoo ong to cool down because of the large ground plane,
thus the solder joint is liquid for a long period of time, and the
component probably moves while the solder is cooling. I thought the proper
term for this was a "disturbed solder joint" not cold solder joint. Just
wondering!?!
Ed Holton
Lectron Products
[log in to unmask]
-------------
Original Text
From: C=US/A=INTERNET/DDA=ID/TechNet-request(a)ipc.ipc.org, on 4/2/97 11:23
AM:
Does anyone have any information on what type of fan (ionizer) works
best at the end of the wave solder machine?
We are having some problem with cold solder joints on some of the
products with large ground planes. They are taking too long to cool. I
was going to place an ionizer that will blow onto the bottom of the
board as it leaves the wave solder machine. We are running an
Electrovert 2000/s.
Also does anyone have any information or experience with how far away
from the wave itself the fan should be placed?
Any help is appreciated.
------------------------------------------------------------------------
-------
Ryan Chase - Manufacturing Engineer
Harris Canada Inc.
Wireless Access Division
(403) 295-5036
FAX (403) 295-8862
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