I vote with Loa. Silkscreens might not be needed in a perfect process with perfect components, but they come in handy when you are trying to find a part referenced in a schematic, ECO, first pass yield report or part placement error report. It is more convenient to grab a board than wait for support documentation to print.
Thank you,
Paul Black
Manufacturing Engineer
Kronos
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of ALLEN, LOA
Sent: Tuesday, May 16, 2006 1:10 PM
To: [log in to unmask]
Subject: Re: [TN] Silkscreen on pads
Regarding Silkscreen markings - Unless you are using ARE (Automatic
Rework Equipment) then AOI, ATE, & X-ray are useless and should also be
eliminated. :)
I vote in favor of leaving silkscreen.
Loa
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Tuesday, May 16, 2006 9:42 AM
To: [log in to unmask]
Subject: Re: [TN] Silkscreen on pads
Silk screen has been redundant for many years unless you are really
testing
by hand.
Let's face it the machine that places components doesn't use it, the AOI
doesn't need it, the ATE can't see it, and the x-ray machine couldn't
care
less.
Remove it all I say,
John
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell
Sent: Tuesday, May 16, 2006 8:37 AM
To: [log in to unmask]
Subject: Re: [TN] Silkscreen on pads
I really makes sense considering the only use for silkscreen in these
times
are hand placement of components and perhaps rework or removal and
repair of
said components.
I've talked to many CM's and OEM's who've stated they could care less
about
the symbolization only to the point it affects component placement.
A show of hands now, who would be comfortable with removing symbol
altogether? Pros of such action, Cons of such action?
Franklin
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey
(AZ75)
Sent: Tuesday, May 16, 2006 10:31 AM
To: [log in to unmask]
Subject: Re: [TN] Silkscreen on pads
This is one of the reasons I don't allow silkscreen on my expensive
printed wiring boards that have to be soldered. I get grief from
everyone, but I never have to scrap a perfectly good functional printed
wiring board, because of a poorly executed questionable at best
manufacturing aid.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, May 16, 2006 5:55 AM
To: [log in to unmask]
Subject: Re: [TN] Silkscreen on pads
It depends.
If the artwork covers major parts of the pads critical to the strength
of the solder joint, then it needs to be removed. If it is a situation
where a very small amount of the epoxy overlaps onto the very edges of
the pads, it may not be so critical. The boards are not any good if even
one pad has an open.
I know that removing the artwork epoxy can be extremely difficult.
I would suggest the board vendor get on the stick and start a rework
process for removing the epoxy. You should reach an agreement that any
rework on your part is paid for by the board vendor.
After the vendor provides you with 100 of the reworked pwbs, build them
up and see how they solder before accepting any more.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Black, Paul
Sent: Tuesday, May 16, 2006 7:46 AM
To: [log in to unmask]
Subject: [TN] Silkscreen on pads
Hi Fellow TechNetters,
I am expecting a fabbed board for our first leadfree production build
next month and have just been informed by the supplier that the artwork
contained silkscreen on quite a few of the solderable SMT pads. They
didn't catch it in time, so now they are asking is we could accept the
boards (qty = 1000) this one time. My PCB spec does not allow silkscreen
on any solderable surface, so I could reject the boards, but my concern
is that there may not be enough time to have more boards fabricated in
time for this build. I know that the boards wouldn't be acceptable per
IPC-A-610, but does anyone have any experience with this situation and
the best way to handle it?
Thank you,
Paul Black
Manufacturing Engineer
Kronos
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