TECHNET Archives

July 2008

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:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Thu, 31 Jul 2008 07:39:04 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (77 lines)
Hi, Gregg
We use a contract manufacturer who has a really good process for adding
compliant S and C leads to QFNs using a process that does not subject
the components to heat. They do really good work for us and it very
effectively fixes the problem. We inspect 100% and then X-ray the parts
when they send them back to us, and we have yet to find a bad solder
joint on the components. Check out www.analog-tech.com. 

  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Temkin, Gregg
Sent: Wednesday, July 30, 2008 4:27 PM
To: [log in to unmask]
Subject: [TN] Use of QFN devices in high reliability applications

Our team is working on several new electronic devices whose application
is primary, flight critical hardware for commercial aircraft.

Our initial component selection includes many QFN packaged devices
(leadless, bottom side termination only) which will be mounted on .063"
FR4 boards using SN63.  The devices range from 20 to 44 terminations.

From studies that are available on the web, a picture has emerged that
QFN packages have reduced long term solder joint reliability when
compared with leaded or some of ball grid array devices.  Board
thickness, flexing and whether the device has a central solderable heat
sink seem to have a significant affect on reliability.  Problem is there
are no absolute numbers, so for critical applications it seems that
thorough testing is required.  We'd rather not wait until the end of a
lengthy test regimen to find we've gone down the wrong path.  Is there
newer information abbailable?   Two of the studies stated that further
testing was being performed to support the reliability requirements for
aerospace and other high-rel applications however I cannot find any
updated information on the web.

We have decided to replace several of the QFN's with leaded devices,
however there are no direct crosses for 3 of the devices. One of them
will require a number of components to create the same function;
possibly an additional circuit card.

Is anyone aware of information or recommendations that would be useful
for our assessment?  Is there any specific information that would drive
us to use or not use them?

Thanks for your help

Gregg






---------------------------------------------------
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