Jim
If you can use the boards with more warpage, then you should, by all means
increase the spec. There's no benefit to making your supplier throw boards
that are functional. The opposite is also true. If you need tighter
requirements, then specify them also. I've had a couple of instances where
I ran into some parts that needed an absolute maximum warpage value rather
than a %. If the warpage exceed a certain amount it interfered with the
cameras on the pick and place equipment. There were multiple parts impacted
by this and each had different dimensions, so the warp as a % was variable
on each part. Some parts ended up with warp specs over 1% while others were
less than 0.5%. The parts we had the biggest problem with were multi-image
arrays with long dimensions and unbalanced, mixed dielectrics. We ended up
working with the customer to re-panelize these so they could accept a higher
warp %.
I agree with the "consensus" that warpage should be evaluated in the panel.
One thing I'm curious is how your fabricator determined that the single
images met the spec. How did they measure it and how did they come up with
a different % value for the image vs the panel? Most of the warped boards
I've seen have a pretty consistent curvature to them and expressed as a %,
the value stays consistent.
> ----------
> From: Marsico, James[SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;Marsico, James
> Sent: Thursday, March 14, 2002 7:01 AM
> To: [log in to unmask]
> Subject: Re: [TN] Board Bow and Twist
>
> What if the panels are bowed beyond the .75% limit, the boards are not, I
> can build them and I can use them? I know I'm answering my own question,
> I
> should use them, right? Well, what's the purpose of the .75% requirement?
> I would think that the requirement should be whatever is agreed upon
> between
> customer and supplier. If I can live with 2%, why not (within reason).
> Jim Marsico
> Senior Engineer
> Production Engineering
> EDO Electronics Systems Group
> [log in to unmask] <mailto:[log in to unmask]>
> 631-595-5879
>
>
> -----Original Message-----
> From: Franklin D Asbell [SMTP:[log in to unmask]]
> Sent: Thursday, March 14, 2002 8:25 AM
> To: [log in to unmask]
> Subject: Re: [TN] Board Bow and Twist
>
> James,
>
> An afterthought, the bow and twist requirement is there to provide
> ease of
> board population as well as end use fit. If the board is warped
> prior to
> assembly, this indeed would affect population thus potentially
> making the
> boards unsuitable for end use...just something to think about, or
> pass along
> to your supplier.
>
> Franklin
>
> ----- Original Message -----
> From: "Marsico, James" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, March 14, 2002 6:48 AM
> Subject: [TN] Board Bow and Twist
>
>
> > I think this is a no-brainer, but here goes... We were
> delivered
> boards
> in
> > panel form from one of our suppliers. At Incoming Inspection,
> the
> panel
> was
> > rejected for excessive bow (>75% for SMT) and returned the
> supplier. The
> > supplier called me and said that even though the panel exceeded
> the bow
> > requirement, the individual boards were acceptable. When I
> quoted
> the bow
> > and twist requirement from IPC-6012, "Panels which contain
> multiple
> printed
> > boards which are assembled on the panel and later separated
> shall
> be
> > assessed in panel form." , he said yes, you measure the
> individual
> boards
> in
> > the panel. I need clarification.
> > Thanks,
> > Jim Marsico
> > Senior Engineer
> > Production Engineering
> > EDO Electronics Systems Group
> > [log in to unmask] <mailto:[log in to unmask]>
> > 631-595-5879
> >
> >
> --------------------------------------------------------------------------
> -------
> > Technet Mail List provided as a free service by IPC using
> LISTSERV
> 1.8d
> > To unsubscribe, send a message to [log in to unmask] with
> following
> text in
> > the BODY (NOT the subject field): SIGNOFF Technet
> > To temporarily halt delivery of Technet send e-mail to
> [log in to unmask]:
> SET Technet NOMAIL
> > To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> > Search previous postings at: www.ipc.org > On-Line Resources &
> Databases >
> E-mail Archives
> > Please visit IPC web site http://www.ipc.org/html/forum.htm for
> additional
> > information, or contact Keach Sasamori at [log in to unmask] or
> 847-509-9700
> ext.5315
> >
> --------------------------------------------------------------------------
> -------
> >
>
>
> --------------------------------------------------------------------------
> --
> -----
> Technet Mail List provided as a free service by IPC using LISTSERV
> 1.8d
> To unsubscribe, send a message to [log in to unmask] with following
> text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> Search previous postings at: www.ipc.org > On-Line Resources &
> Databases > E-mail Archives
> Please visit IPC web site http://www.ipc.org/html/forum.htm for
> additional
> information, or contact Keach Sasamori at [log in to unmask] or
> 847-509-9700 ext.5315
>
> --------------------------------------------------------------------------
> --
> -----
>
> --------------------------------------------------------------------------
> -------
> Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt delivery of Technet send e-mail to [log in to unmask]:
> SET Technet NOMAIL
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> Search previous postings at: www.ipc.org > On-Line Resources & Databases >
> E-mail Archives
> Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
> information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> ext.5315
> --------------------------------------------------------------------------
> -------
>
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
