Mark,
Your best source is your manufacturer.
James made a good point about re-flowing instead of wave soldering.
However, I've had design situations where both were requested - re-flow
for the top side and glue & wave for bottom side with the through hole
components.
If you re-flow the bottom components, a fixture is built to keep the
SMT's from falling into the solder during wave of the TH components. It
all depends on which is going to be cheaper, make a fixture to protect
the SMT components during wave of the TH's or gluing them and allowing
them to go through the wave or hand soldering the TH components and
re-flow all the SMT's. IC's with a 50mil pitch can be wave soldered,
but if you're using less than that, most mfg's won't do it. I haven't
had 0402's wave soldered, but I have requested 0603's to be wave
soldered.
Direction of your components and "shadowing" (larger components in front
of smaller ones) are very important considerations when wave soldering.
You will need to know which way the boards and panels are going through
the wave and place your components accordingly. Also, thieving pads are
added at the trailing end of IC's when going through a wave. If you're
using QFP's, they have to be handled differently. Some companies put
them on a 45 degree diagonal, while others hand solder them afterwards.
Each of these will take up space on your board.
It really does depend on your manufacturer. There can be specific
spacing requirements for the mixed technology of TH and SMT that can
surprise you (in a very space consuming way). These are different
depending on your manufacturer and how much you are willing to spend.
Good luck,
Cherie Litson, CID
Sr. PCB Designer
Nytec, Inc.
-----Original Message-----
From: Mark Holmes [mailto:[log in to unmask]]
Sent: Friday, September 07, 2001 8:18 AM
To: [log in to unmask]
Subject: [DC] Wave Soldering SMT
Hi all!
Can anyone help me find a good source of info regarding wave soldering
SMT components? I am particularly interested in when a component is
to small or too large to be considered for wave soldering. What is the
minimum pitch, and max number of pins for ICs etc.
Thanks in advance.
Regards,
Mark.
Mark Holmes PCB Designer
Helvar Merca Ltd.
Hawley Mill, Hawley Road,
Dartford Kent.
DA2 7SY England.
Tel: +44 (0)1322 222211
Fax: +44 (0)1322 282286
mailto:[log in to unmask]
Visit our NEW Lighting Control website at:
http://www.helvar.co.uk
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