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May 2006

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Subject:
From:
David Greig <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, David Greig <[log in to unmask]>
Date:
Tue, 16 May 2006 20:08:23 +0100
Content-Type:
text/plain
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text/plain (222 lines)
Speaking as a designer (analog,RF,SI,FPGA,DSP,PCB's & SW), can we also agree that test points are a waste of space and things
function better without them anyhow.

Silkscreen is damn handy in the lab, but one might reasonably loose it all together if assembly and test folk would happily
accept complete absence of test points! All they need to do is stick the bits down right first time anyhow...

Best Regards

David Greig
______________________________
GigaDyne Ltd
Buchan House
Carnegie Campus
Dunfermline KY11 8PL
United Kingdom
t: +44 (0)1383 624 975
www.gigadyne.co.uk
______________________________

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Black, Paul
Sent: 16 May 2006 19:46
To: [log in to unmask]
Subject: Re: [TN] Silkscreen on pads

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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