TECHNET Archives

August 2007

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Jack Crawford <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jack Crawford <[log in to unmask]>
Date:
Wed, 8 Aug 2007 10:29:44 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (153 lines)
Bev, thanks for your detail on this. One additional consideration is
cost and availability of a replacement assembly. Bottom line--every
soldering temperature excursion has a detrimental effect on the
assembly. Maybe a little or maybe a lot (see Bev's list of variables).

There was an Air Force spec that limited the number of rework/repair
operations, but unless every assembly has a unique serial number and
there is a complex, globally accessible database, how will a person know
if a particular component has already been removed/replaced three times?
Yes, depending on the skill of the technician, there may be evidence of
a rework but three times will look the same as one time.

Any limitations have to be established by a product owner based on info
that only they know, it isn't possible for the IPC committees to set
those limits.

Cordially,
Jack

Jack Crawford, IOM
IPC Director Certification and Assembly Technology
[log in to unmask]
847-597-2893
FAX  847-615-5693
3000 Lakeside Drive, Suite 309 S
Bannockburn, IL, 60015

-----Original Message-----
From: Bev Christian [mailto:[log in to unmask]]
Sent: Tuesday, August 07, 2007 8:53 AM
To: TechNet E-Mail Forum; John Burke
Subject: RE: [TN] Rework question

John,
I am having people look, but if there is a limit I do not remember.
However, from a practical point of view, the answer is Doug Pauls'
patented (Or is that copyrighted or trade marked? Being a lawyer, I
don't know.) phrase, "It all depends".  It depends on the method of
rework, (reflow, wave solder, selective soldering, soldering iron, hot
air gun focused IR, flame), temperatures reached, ramp rates, dwells,
size of board, thickness of board, type of component, heat sinks, skill
of operator. I could go on.  Make yourself a fishbone diagram.

And then are we talking about say 3X of the same component, or 5X
side-by-side or 7x but each in a thermally separated area from the other
six?

Here's a scenario for you: double sided reflow and then required rework
under cans on both sides of the board. So this means two more for can
removal, dressing the can pads, removing the components, dressing the
pads, part deposition, can replacement.  And hope everything works!

So you need visual inspection, x-ray inspection, electrical test and if
you really want to do it right, x-sectioning and a whole battery of
reliability testing.

I have seen good work and I have seen thin boards delaminated after a
single, poor attempt at rework.

Bev
RIM 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Tuesday, August 07, 2007 10:29 AM
To: [log in to unmask]
Subject: [TN] Rework question

Hi,

 

I had a question yesterday which was "has the number of re-work cycles
allowed by IPC changed for lead free?"

 

And I confess I don't know but I bet someone on this link does.

 

If you could let me know number of thermal cycles allowed and the spec
reference I would be grateful.

 

John

 

 

 

John Burke

 

(408) 515 4992

 


---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or
(re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing
per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/archives
Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------

---------------------------------------------------------------------
This transmission (including any attachments) may contain confidential
information, privileged material (including material protected by the
solicitor-client or other applicable privileges), or constitute
non-public information. Any use of this information by anyone other than
the intended recipient is prohibited. If you have received this
transmission in error, please immediately reply to the sender and delete
this information from your system. Use, dissemination, distribution, or
reproduction of this transmission by unintended recipients is not
authorized and may be unlawful.

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET
Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the
posts: send e-mail to [log in to unmask]: SET Technet Digest Search the
archives of previous posts at: http://listserv.ipc.org/archives Please
visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------

ATOM RSS1 RSS2