Hi folks! Good to see you again John - figured you were lurking out there somewhere! It is very interesting that the MLCC fabricators have a large number of solder process recommendations but very few requirements (a requirement is not a requirement unless someone is willing to pay for it). A better explanation/example would be the MLCC recommendation to not manually solder chip capacitors - you won't see this recommendation as a requirement! The information and recommendations the MLCC vendors give is good information but also should not be taken as gospel (as John pointed out). Manual soldering of chip capacitors can be done very reliably with proper procedures and equipment. A fair segment of the industry has been reflow soldering MLCCs with ramp rates in the 2-6 C/sec range very successfully for many years. There are certain aspects of those processes which should be carefully monitored - understanding the process/component interaction is key to avoiding failures. Blind faith of a specific parameter is a bad thing. Dave Hillman Rockwell Collins [log in to unmask] John Maxwell <[log in to unmask] To: [log in to unmask] M> cc: Sent by: TechNet Subject: Re: [TN] Preheat of ceramic chip capacitors <[log in to unmask]> 09/04/2003 11:14 AM Please respond to "TechNet E-Mail Forum."; Please respond to John Maxwell 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------