Mark
I am not going to claim to be and expert on this topic because I have just
recently started to support this process my self, but I too have come across
this problem.
Something to look at, for solder being pushed through the routed slots.
Is the board warping letting the routed slots fall deep into the wave and
scooping the solder on top?
If this is the case you might need some extra board support such as a
pallet or some kind of top support. Another possible solution to this is
having your panelized boards scored instead of routed, this will make the
panel much stiffer and actually eliminate the routed slots.
If the board is not warping you could try blocking the slots with some tape
or a peelable solder mask.
As for the skips, this should be able to be corrected through wave
adjustments or conveyor speed if the board is not warping.
Hope this is of some use.
Trevor Goddard,
SMT Supervisor
XLTEK
(905) 829-5300 x 348
[log in to unmask] <mailto:[log in to unmask]>
-----Original Message-----
From: Mark Holmes [mailto:[log in to unmask]]
Sent: Friday, September 29, 2000 7:42 AM
To: [log in to unmask]
Subject: [TN] Problems Wave soldering SMT.
Hi all,
We are currently having problems with one of our boards which requires SMT
parts on the underside to be wave soldered.
The problems include solder bridges and solder skips. All the components are
orientated as IPC-782-3-9, although they do
appear to be pretty closely placed. The board was designed some 5 years ago
by an outside contractor, and at the moment
I don't have the design data available to modify. Although the board is an
old design, we have had many changes at our
manufacturing plant, both with equipment and personnel, and the new operator
is struggling to get good results with this
particular board.
One point raised in a recent meeting was that they were unable to make
certain adjustments to the wave, which might
solve the problem, because the solder was being pushed through the routed
gap between the board and the panel.
Our routed gap between boards tend to be 2.4mm, which from my experience
seems to be fairly standard.
My questions are:
* Should a 2.4mm routed gap around a board cause problems when wave
soldering?
* What standards detail component to component spacing for wave
soldering SMT?
I have the IPC standards which details land to land clearances (IPC-782-3-8)
but these only appear to be for reflow.
My design guidelines state that the minimum distance between shadowed
components should be no less than the
height of the component next to it. What about parts that are not shadowed?
- ie end to end clearance of chip components
(assuming orientation is as IPC-782-3-9)
Any thoughts or comments would be most appreciated.
Thanks in advance,
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]
http://www.helvar.com
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