John,
Wonderful answer. I didn't want to say in my earlier response that the 2C/sec. gideline was a number "invented" by ceramic component vendors to make it easier to blame crack caps on assembly processes rather than components. It's nice to hear the truth about party lines from an x-party member.
PS: Do you happen to have Bob Checkaneck's current contact information?
Regards,
George
George M. Wenger (908)-546-4531
Reliability Engineer
RF Power Amplifier Group
Andrew Corporation, 40 Technology Drive, Warren, NJ 07059
[log in to unmask]
-----Original Message-----
From: John Maxwell [mailto:[log in to unmask]]
Sent: Thursday, September 04, 2003 12:14 PM
To: [log in to unmask]
Subject: Re: [TN] Preheat of ceramic chip capacitors
Hi Daan,
Preheat rates is one of the most confusing guidelines ever stated by MLCC
vendors. If you ask them specifically where the numbers come from,,, well
don't be surprised by the answers. Basically those guidelines are vapor (or
perhaps vapour) especially when you consider that billions are wave
soldered each year and exposed to rates of change exceeding 100C/sec with
no cracking. I would look first at board handling for 0805 sized chips and
possibly fillet size and cooling rates. If parts were larger cooling rates
become more important. For those that want to rush to point out in some of
my much earlier publications that I repeated the party line of 4C/sec, it
was just that, a party line.
Basically you can't crack 0805 sized MLC capacitors during reflow during
the heating stage. Cool down is not very likely unless you are using
hurricane cooling fans and huge bulbous solder joints.
John Maxwell
At 05:32 PM 9/4/2003 +0200, you wrote:
>Hi Technet,
>
>I just saw a specification for the soldering profile for a simple
>0805-sized ceramic chipcapacitor. It mentions a maximum preheat ramp,
>both for wave and for reflow soldering, of 2 degrees Celcius per second.
>
>In the beginning of the slope, for some of our products, we go slightly
>higher than this.
>One of our customers now thinks that the preheat ramp being steeper
>than the component suppliers specification must be the reason for
>malfunctioning of this specific part.
>
>I won't annoy you with all the discussions we had and the
>investigations that we've done, I just hope to get an answer to the
>following question: is it possible that a preheat ramp of 3 °C/s results
>in failures (but without any visible damage) of 0805 ceramic
>chipcapacitors ?
>
>Best regards,
>
>Daan Terstegge
>Thales Communications
>Unclassified mail
>Personal Website: http://www.smtinfo.net
>
>---------------------------------------------------
>Technet Mail List provided as a service by IPC using LISTSERV 1.8e
>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
>847-509-9700 ext.5315
>-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 847-509-9700 ext.5315
-----------------------------------------------------
------------------------------------------------------------------------------------------------
This message is for the designated recipient only and may
contain privileged, proprietary, or otherwise private information.
If you have received it in error, please notify the sender
immediately and delete the original. Any unauthorized use of
this email is prohibited.
------------------------------------------------------------------------------------------------
[mf2]
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 847-509-9700 ext.5315
-----------------------------------------------------
|