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December 2003

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 10 Dec 2003 09:54:43 +0200
Content-Type:
text/plain
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text/plain (152 lines)
Doug

I've been using an automatic e-mail sorter, called POPFile, for many
months and I thought I'd just about got everything working well, with
something like 99.9% accuracy into 12 mailboxes. Then a certain guy from
Rockwell Collins comes along and upsets the apple cart. How? He adds a
PS to his message, saying "Lets see how many out of office replies I get
on THIS one.....". Dang me! The system's parser interprets this as an
'out of office' message :-( And Bev's reply, to boot. Just when I
thought I could automatically delete all these messages, rather than
send 'em to a 'check' mailbox, you happen to prove me wrong. These two
are the first false positives for weeks :-(

Grrrrrrrrrr! Back to the drawing board!

:-)

Best regards,

Brian

Doug Pauls wrote:
> Depends... just kidding!
> **And I bet it just tickles you pink to use my favorite expression back at
> me!
>
> "Our specifications are based on solder joint connections and the solder
> specifications are not in question."  What does this mean?
> What solder joint requirements?
>
> **What, you can't read my mind?  Shocking.  OK, here is an example.  If I
> pick up a copy of IPC-A-610 (Rev C), and I go to section 12.2.2.1 Chip
> Components - Rectangular or Square End Components, Side Overhang, the
> target is no overhang.  It becomes a defect for class 3 when overhang
> exceeds 25%.  Looking at the requirements for end overhang, none is
> allowed.  These requirements come as the result of many solder reliability
> studies, and are based on the dynamics of a metallic solder joint.
>
> Now suppose we replace the solder material with a silver filled epoxy
> adhesive.  Different material, different dynamics.  Should these same
> solder joint requirements of 25% side overhang and 0% end overhang be
> applied to the conductive adhesive joint?
>
> I was looking for any studies that have delved into this issue.  Could I
> allow more side overhang or some end overhang because I am now using a
> different material with different mechanical bonding strengths and
> different creep characteristics?  Or, is it not as reliable as solder
> (Hillman, shup up)and we should require less overhang?
>
> Jack Crawford, does the IPC have a specification like A-610 which addresses
> the issues of electrical connection using conductive adhesives?
>
>
> Is epoxy rigidity good or bad? Is it brittle?  Is it stronger?
> <grin> It depends.  I think you get better mechanical strength from the
> epoxy, but at the cost of reworkability.
>
>
> Doug Pauls
> Rockwell Collins
>
> Lets see how many out of office replies I get on THIS one.....
>
>
>
>                       "Bev Christian"
>                       <[log in to unmask]        To:       "TechNet E-Mail Forum." <[log in to unmask]>, <[log in to unmask]>
>                       et>                      cc:
>                                                Subject:  RE: [TN] Adhesive strength vs. overhang
>                       12/09/2003 02:23
>                       PM
>
>
>
>
>
>
> Doug,
> Depends... just kidding!
> "Our specifications are based on solder joint connections and the solder
> specifications are not in question."  What does this mean?
> What solder joint requirements?
> Is epoxy rigidity good or bad? Is it brittle?  Is it stronger?
>
> No, I do not know of any public report of the type you are talking about.
> I would expect some of the big boys have their own internal ones.
> Bev Christian
> Research in Motion
>
>
> -----Original Message-----
> From: Doug Pauls [mailto:[log in to unmask]]
> Sent: December 9, 2003 3:14 PM
> To: [log in to unmask]
> Subject: [TN] Adhesive strength vs overhang
>
>
> Good afternoon all,
>
> Internally, we are having discussions on the amount of allowable overhang
> of passive SMT components (R and C).  Our specifications are based on
> solder joint connections and the solder specifications are not in question.
> We have an application where a silver filled adhesive is used to make the
> connection between SMT metalization and mounting pad.  The solder joint
> requirements were applied to these adhesive joints and I am wondering as to
> the validity of this.  The adhesive is epoxy based and, in my mind, more
> rigid than solder.  I think we are unnecessarily rejecting parts that are
> acceptable.
>
> So, before I go off and do a complex designed experiment, I thought I would
> check with the Technet crowd first.  Do you know of any studies that show
> the adhesive force (e.g. pull strength) vs. the degree of pad overhang?
>
> Doug Pauls
> Rockwell Collins
>
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