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Date: | Thu, 23 Oct 1997 14:08:44 -0500 |
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Bill,
Thanks for the SMT wave soldering recommendations. One question I have is:
what are "solder thieves"?
Thanks again for the info.
Erik Olson
Westell, Inc.
[log in to unmask] on 10/23/97 12:54:46 PM
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Subject: Re: [TN] Wave soldering SMD actives
Bryan:
A few rules to guide you down the path:
1) Gluing components is no problem. However, you don't need solder
paste for the bottom side, since the wave soldering operation makes
the electrical connection.
2) Nitrogen is NOT required.
3) Do NOT use components larger than SO28 in wave solder.
4) Do NOT use ICs with lead pitch < 0.050" pitch. If so, bridging is
almost guaranteed in the wave.
5) Components need to be mounted with leads parallel to the wave. That
way, the body of the IC will not create shadow voids or solder skips
on the trailing side of the IC. The same rule applies for passives;
parallel to the wave prevents shadowing.
6) IC and passive component land patterns may need to be extended
slightly to guarantee wetting by the wave. Rule of Thumb: The pad
should extend outward from the component >= to the height of that
component.
7) Do NOT mount tall components on the bottom side of the board. Not
only is there a land pattern consideration but also a clearance to the
edge of the solder pot. I would limit the height of bottom-side
components to the thickness of the SO-28 (~0.070" MAX)
8) Do NOT use PLCC or QFP packages on the wave solder side of the
board. See #3, #4 & #5.
9) Solder thieves are helpful on the leading and trailing leads of the
IC. That way, if the board in placed in the wave solder BACKWARDS, it
will still do OK.
10) If the board is to be ICT tested, I STRONGLY recommend water wash
vs.
no-clean. The flux acts as an insulator, it creates "false fails" or
"flase opens" in ICT and also gums up the test points of the ICT
fixture.
Now that you know "where the rocks are", you can APPEAR to "walk on
water"!
Good Luck!
Bill Fabry
Plantronics, Inc.
345 Encinal St.
Santa Cruz, Ca. 95061
(408) 458-7555
e-mail: [log in to unmask]
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Subject: [TN] Wave soldering SMD actives
Author: "TechNet Mail Forum." <[log in to unmask]> at INTERNET
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