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May 2006

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Subject:
From:
"Kane, Amol (349)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Kane, Amol (349)
Date:
Mon, 22 May 2006 13:57:26 -0400
Content-Type:
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text/plain (140 lines)
Hi,
We use type UR, AR, SR coatings to coat boards. Urethane coatings are hard (stiff) coatings that lead to these defects as they cannot yield to the expansion/contractions during thermal cycles. Is there a specific reason (property) of 1A20 that you use it for?. Another suggestion to this problem would be to use acrylic coatings (1B31, 1B73 etc)

Sincerely,
Amol Kane
M.S (Industrial Eng.)
Process Engineer
Harvard Custom Manufacturing 
941 Route 38  Owego, NY 13827
Phone: (607) 687-7669 x349
[log in to unmask]

 -----Original Message-----
From:   TechNet [mailto:[log in to unmask]]  On Behalf Of Marsico, James
Sent:   Monday, May 22, 2006 1:17 PM
To:     [log in to unmask]
Subject:        Re: [TN] Cracked ICs

Hello, again...
All indications are leading to the conformal coating as the culprit for the
cracked 8-pin DIPs.  The urethane coating (Humiseal 1A20) is dip-applied,
and a typical assembly has bridging between the component body and the PWB,
as well as between the component body and the leads.  Ten ESS thermal cycles
of -51 to +85C prior to coating showed no cracks, but samples cycled after
coating had some cracks.  My suggestion to the supplier was to spray-apply
the coating and inspecting for coating bridging.

Have you experienced anything like this before?

Jim Marsico
Senior Engineer
Production Engineering
EDO Corporation
[log in to unmask] <mailto:[log in to unmask]>
631-630-5079


        -----Original Message-----
        From:   Russ Winslow [SMTP:[log in to unmask]]
        Sent:   Wednesday, May 10, 2006 5:58 PM
        To:     TechNet E-Mail Forum; Marsico, James
        Subject:        RE: [TN] Cracked ICs

        Hello James,
        Here are a few things to look for.  The 8-pin cerdip package does
not have much surface area for the glass seal especially if the die is
large.  A lead forming step prior to board assembly could be the cause.  If
you are forming the leads inward be certain that only the minor leads (the
skinny portion) are being bent.  If the major leads (the wide portions) are
bent simultaneously then you may very well pop the cap from the base or
cause these perimeter cracks.  Another thing to look for is cracks before
board assembly.  Cerdips are prone to glass cracking caused by tube to tube
handling.  I have never heard of cracking due to reflow process unless you
are doing vapor phase without preheat.  Some automatic lead straighteners
will crack 1000 units per hour so do not let them come anywhere near your
glass sealed components.  Another cause could be a lead tinning (hot solder
dip) step.  Without proper preheat a supplier could cause serious damage to
the glass seal.

        If you send me a sample I can probably tell you much more. (no
charge!)

        Regards,
        Russ Winslow

        Six Sigma
        905 Montague Expwy
        Milpitas, CA  95035

        [log in to unmask]
        www.sixsigmaservices.com
        Phone (408) 956-0100 x 111
        Fax   (408) 956-0199


        -----Original Message-----
        From: Marsico, James [mailto:[log in to unmask]]
        Sent: Wednesday, May 10, 2006 6:11 AM
        To: [log in to unmask]
        Subject: [TN] Cracked ICs


        Hello Technet,

        We're seeing a recurring problem of a cracked ceramic IC, assembled
on a
        through-hole PWB.  The component is an 8-pin DIP, T.I. P/N
5962-9452601QPA .
        The crack is located below the lead frame and radiates all the way
around
        the device.  Has anyone experienced this before?

        Please respond directly to me, as I cannot receive e-mails from
Technet.

        Thanks in advance,

        Jim Marsico
        Senior Engineer
        Production Engineering
        EDO Corporation
        [log in to unmask] <mailto:[log in to unmask]>
        631-630-5079

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