RO 4350 has a lower bond strength when compared to FR4. TO combat this, a higher profile foil is used to improve the peel performance. When the PCB house uses 4350 in a foil build and is bonding with RO 4450, the foil treatment needs to be specific to maintain bond strengths. Not using the correct foil type will produce poor bond strengths which maybe a learning curve for the PCB house. If the build is a core build, with RO4350 from L1/2: Ln/Ln-1, then the bonding mechanism is controlled by Rogers. The PCB supplier should be able to interface with Rogers to obtain the lot testing information and assess of the peel numbers are out of specification. A microsection of the PCB will also show the foil profile characteristics and determine the build used. Jeffrey Bush Director, Quality Assurance and Technical Support VERMONT CIRCUITS INCORPORATED 76 Technology Drive - POB 1890 Brattleboro, Vermont 05302 Voice - 802.257.4571 ext 37 Fax - 802.257.0011 <http://www.vtcircuits.com/> -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D. Sent: Thursday, January 19, 2006 5:09 PM To: [log in to unmask] Subject: Re: [TN] PWB SMT pad retention The boards are made of Rogers 4350 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Sherif Refaat Sent: Thursday, January 19, 2006 11:31 AM To: [log in to unmask] Subject: Re: [TN] PWB SMT pad retention Hi Richard, What kind of laminate is that? I had similar problem, few years ago, repairing boards built using "Thermount" (Aramid). That was one of the draw backs of this laminate. The new version of "Thermount" suppose to be better in terms of peel strength, but I don't know if it is close enough to that of FR4. Sherif Refaat, ----- Original Message ----- From: "Stadem, Richard D." <[log in to unmask]> To: <[log in to unmask]> Sent: Thursday, January 19, 2006 11:42 AM Subject: [TN] PWB SMT pad retention Hi, Folks, Is there a standard that specifies how well SMT pads should adhere to the pwb? By pads I mean BGA pads that have no trace attachment, and I.C. (gullwing) pads. A client has circuit boards with pads that come off extremely easily during standard rework and reflow processes. It is not limited to the BGA pads, many other unused I.C. lead pads are also being found out of place in the solder joints after reflow, and are easily peeled away. The pads are not tiny flip chip pads, but standard .035" diameter pads and rectangular .020" by .030" pads. The reflow peak temperature is only 210 deg. C for about 40 seconds. The rework is at 200 C. for 30 seconds. Also, any speculation on the cause? This problem is limited to a single PWB part number. --------------------------------------------------- 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- 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 847-615-7100 ext.2815 -----------------------------------------------------