Interesting, the boards are hot air leveled (HAL), if inspected to
IPC-A-600, sect 2.4.1 Nonwetting, states that this is a non conforming
condition for all classes of products, Class 1, 2, 3,. The issue being, if
the boards are hot air leveled and there is exposed copper means that non
wetting is occurring and this is not acceptable. The basis material is
exposed and it is not supposed to be exposed.
IPC-A-610, the assembly document states in sect 6.5.6 Nonwetting that this
is a defect for Class 1, 2, 3, if solder is required. Since this board is
HAL, solder is required and therefore it again does not meet the
requirements of the specification.
So my opinion at this point is that the board is rejectable.
Now for the reality. Exposed copper will not cause you a problem, many
products have been built through the years with exposed copper, if not on
the ends of the component leads, along the edges of all the conductor
traces. And by the way go check your plumbing in your house and let me know
how your copper pipes are doing after all these years. We also have boards
that are OSP protected, once these boards are soldered the OSP coating is
for all practical purposes gone, so you have exposed copper all over the
board if the solder did not wet to the edges of all the pads. Some companies
have been building boards like this for over 20 to 25 years.
What to do? Identify the condition as a defect due to it does not meet the
specification, work with your subcontractors to get their act together, and
disposition the boards to use as is.
That's my cut at it. Will be interested to hear what others have to say.
Leo Lambert
Technical Director
EPTAC Corp
[log in to unmask]
www.eptac.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Mario Dion
Sent: Thursday, November 06, 2003 5:10 PM
To: [log in to unmask]
Subject: [TN] Assembled pcb with exposed copper; is conf.coating
appropriate to "isolate" the exposed copper ?
Bonjour Technetters,
Would a pcb assembly with exposed copper around some vias be reliable if
fully coated with conformal coating so copper won't be exposed anymore ?
The problem was not detected at the incoming inspection so many pcb were
assembled. Board finish is HASL.
Thanks for your comments,
Salutations,
___________________________
Mario Dion, T.Sc.A./ A.Sc.T.
Production Engineering
Mediatrix Telecom Inc.
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