I would be quite worried at what I see here. To me, it looks like vesication. This is caused by the solder mask being placed over a hygroscopic contaminant. As the mask is semi-porous (as are all polymers), the contaminant absorbs moisture and forms the bubble where adhesion is poor. Note that there is a halo round each defect; this could be because the pressure in the bubble rises and tends to pull the mask off. You can confirm this possible diagnosis by autoclaving a board in steam, using a domestic pressure cooker for 24 h or so (making sure that it never boils dry). If the problem appears worse, then it is confirmed. Brian (not brain: I lost that many years ago!) Luan Nguyen wrote: > Sorry! I send you file attached but maybe you will not receive it. You > can see the picture on > http://picasaweb.google.com/johnynhluan/BubbleDefectOnPCB > > Best regards, > > >>>> [log in to unmask] 10-Jan-08 08:32:31 >>> > Thank you Brain! > I have some pictures of this defect to refer. > Please give me a advice for this defect. > > Thanks and best regards, > > >>>> [log in to unmask] 09-Jan-08 13:37:58 >>> > If there is one >0.25 mm, then the board should be rejected. > If there are 3 or more of <0.25 mm the board should be rejected. > > Furthermore, and this is my opinion, if a bubble <0.25 mm is between > two > tracks and occupies >50% of the spacing between the tracks, it should > also be rejected. > > Brian > > Luan Nguyen wrote: >> Dear Technet, >> Our company were been happening a problem on PCB, details: >> Per IPC-A-600, Revision G >> 2.9 SOLDER RESIST (Solder Mask) >> 2.9.4 Blisters/ Delamination >> - Acceptable - class 2,3: >> . Two per side not exceeding 0.25 mm [0.00984 in] in the greatest >> dimension. >> >> According to our understanding: >> - If there are 3 bubbles and each of them is exceeding 0.25 mm in > the >> greatest dimension per side, this is defect. >> - In case, if there are more than 3 bubbles and each of them is not >> exceeding 0.25 mm in the greatest dimension per side, this is defect > or >> accept ??? >> Please help us understand clearly it. >> >> Thanks and best regards, >> >> >> *************************** >> Nguyen Hoang Luan >> QC&Training Supervisor >> Spartronics VietNam Co, Ltd. >> No.3, Street No.6, VSIP >> Th An Dist., BDuong Prov., VN >> Tel: (84-650) 784 890 >> Fax: (84-650) 784 891 >> Mobile: 090.3.667448 >> Email: [log in to unmask] >> *************************** >> >> --------------------------------------------------- >> 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 > ----------------------------------------------------- > > --------------------------------------------------- > 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 > ----------------------------------------------------- > --------------------------------------------------- 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 -----------------------------------------------------