Paul, Do you know what the failure mechanism is for these modules? Are the solder joints cracked? One of the more common failure mechanisms for LCCC's are cracked solder joints due to thermal coefficient of expansion (TCE) mismatch between the LCCC and the substrate (FR-4?). Stress induced by temperature swings encountered in operation (ambient temperature changes, power cycling, etc.) cause the solder joint to fatigue and fail. If you are using no clean solder paste, then the flux should remain benign and not cause a problem in service. Howard A. Cyker Lucent Technologies New Product Engineering Email [log in to unmask] Phone 978-960-2964 -----Original Message----- From: Paul Baine [mailto:[log in to unmask]] Sent: Tuesday, March 20, 2001 10:23 AM To: [log in to unmask] Subject: [TN] Solder flux under LCCs Hello. This is the first time I have used IPC TechNet, so please forgive me if this question has been asked before. Our company has built some SEM Modules (Standard Electronic Modules) for a customer who recently reported failures in the field with these Modules. These types of Modules have Leadless Chip Carrier ICs with castellated terminations on them. The solder pads are underneath the IC packages. As part of the failure analysis performed by the customer, some of these LCCs were removed, and they noticed an off-yellow coating on the bottom of the LCCs which they feel is solder flux. They theorize that the solder flux has hardened over time and has become conductive. Our Production Manager thinks that this problem is caused by the fact that these LCCs sit flat on the substrate and therefore the solder flux gets trapped under the LCC during reflow and cannot be cleaned out. He proposes two possible solutions: - put adhesive under the LCC - put a spacer under the LCC which is dissolvable in water (i.e. during cleaning) I was wondering if anyone had experienced a similar problem and knew of an "industry standard" solution, or any solution. Thank you in advance. Best regards, Paul Baine Q.A. Manager C-Tech Ltd., Cornwall, Ontario, Canada ---------------------------------------------------------------------------- ----- 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 the following message: SET Technet NOMAIL 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 the following message: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------