Flux can work fine in a well defined process but paste is better. However, over the last few months of training workshops in Europe and overseas I have been using dip paste designed for STACK Package assembly. The suppliers have not been offering it for rework but it's a joy to use with no stencil costs, just dip and go. I feel sure the main suppliers should offer it even at a higher price! With good housekeeping the material lasts a long time Videos as always to show with some still images as well, With flux www.smartgroup.org/pop/stack4.wmv With paste www.smartgroup.org/pop/stack013.wmv Dip paste images www.smartgroup.org/pop/bobwillisdippaste.gif I cant remember if we have added some POP package defects on the Defect Database at NPL yet but will have to check http://defectsdatabase.npl.co.uk Many thanks Bob Willis 2 Fourth Ave, Chelmsford, Essex, CM1 4HA England Tel: (44) 1245 351502 Fax: (44) 1245 496123 Mobile: 07860 775858 www.ASKbobwillis.com PCB Design for Manufacture & Assembly Workshop 15th October www.ASKbobwillis.com PCB Inspection & Quality Control Workshop 3rd November www.ASKbobwillis.com/faworkshops.pdf Book Bob's "Step by Step Failure Analysis Workshop" 4th November www.ASKbobwillis.com/faworkshops.pdf -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards Sent: 03 June 2009 17:43 To: [log in to unmask] Subject: Re: [TN] BGA-113 package Steve, I would not recommend you only use flux to reflow the BGA... I have had to rework a lot of BGAs because someone thought that that would be a reliable process for rigid PCBs... Paul Paul Edwards Surface Art Engineering -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Kelly Sent: Wednesday, June 03, 2009 9:10 AM To: [log in to unmask] Subject: [TN] BGA-113 package Hi All, We have a rigid flex that has a BGA-113 (microstar BGA) package to be mounted to it. The routing in this area on the top layer leaves me with 0005 of soldermask clearance from the edge of the BGA pad and .003 distance from the edge of the soldermask to the nearest track- in other words I have 0035 of clearance from pad edge to next track assuming a perfect etch and perfect soldermask registration. Having rooted around Texas Instruments web site I believe that it may be possible to reflow this BGA without adding solder paste to the pad - just letting the ball collapse do the attachment. If my scenario is correct I could open up the soldermask and not have too many concerns about bridging between the BGA pads and the tracks. Any thoughts or comments would be appreciated. Thanks Steve Kelly Steve Kelly (PLEASE NOTE NEW E-MAIL ADDRESS) (416) 750-8433 (work) (416) 750-0016 (fax) (416) 577-8433 (cell) --------------------------------------------------- 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 ----------------------------------------------------- =========================================================================== == This email and any attachments thereto may contain private, confidential, and privileged material for the sole use of the intended recipient. 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