Hi Cedric, to solder such components nearly void free I suggest to use a vacuum vapour phase soldering system. On standard PCBs we run automotive products with low void paste, which is solder paste with less flux, through reflow. The paste reduce the void rate about 10%, additional nitrogen (oxygen less than 100ppm during lead free reflow) can reduce by additional 10% to nearly 5% void rate. Best regards, Torsten i.A. Dipl.Ing.(FH)Torsten Hagge tech. projectmanager Kristronics GmbH Gewerbegrund 5 - 9 24955 Harrislee Tel.: +49 461 7741 624 Fax: +49 461 7741 642 [log in to unmask] www.kristronics.de Gerichtsstand Flensburg, Handelsregister: HRB 1433 FL Geschäftsführer Dipl.-Ing. oec. Thormod Ohm Ust-Id-Nr. DE 811182059 Bankverbindung: Deutsche Bank AG Flensburg, Konto-Nr. 4216610, BLZ 21570011 IBAN: DE32 2157 0011 0421 6610 00, BIC: DEUT DE HH 215 -----Ursprüngliche Nachricht----- Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Cedric ORAIN Gesendet: Donnerstag, 17. Februar 2011 15:26 An: [log in to unmask] Betreff: [TN] Voids issue on Aluminium base plate Dear Technetters, We have to solder a RF power transistor onto an aluminium base plate and we are facing with a very challenging issue. We encountered a high voids rate (>30% or 40%) underneath the component body (which is about 35x10mm). This is not acceptable for this application. The component is Nickel/gold plated whereas the aluminium baseplate is plated with Nickel and Silver and then cleaned with solvent. We tried to change/adapt: - soak time of the profile, - 2 difference solder pastes (SAC305), - change the screen design and thickness Finally none of these parameters looks to have significant effect on voids rate. We are now wondering if the solderability of the Ni/Ag plating is good enough and even if it is convenient for that purpose. Is somebody could give us advises? How to enhanced NiAg plating solderability (acid ?!, ...)? Which flux could help to compensate the poor wettability? Which kind of plating would be preferable? ... Thanks and regards, Cedric -----Message d'origine----- De : TechNet [mailto:[log in to unmask]] De la part de Douglas Pauls Envoyé : jeudi 17 février 2011 14:07 À : [log in to unmask] Objet : Re: [TN] Electrical Clearance as stated in IPC standards Good morning Wee Mei, IPC-T-50, the IPC "dictionary", lists the following: Electrical Clearance: The shortest distance between two conductors, which includes traces, terminals and structures, measured through the air. IPC-T-50 does not contain terms for Clumpy, Trucklett, or Bobby Dazzler..... Doug Pauls Lum Wee Mei <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 02/16/2011 11:26 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Lum Wee Mei <[log in to unmask]> To [log in to unmask] cc Subject [TN] Electrical Clearance as stated in IPC standards Dear All, Until now, I am still very curious about this term "electrical clearance" that is used on the IPC standards. Very often, the standard will says something like "it is acceptable as long as it meets the electrical clearance". As I did not have the IPC standards with me when I right this, allow me to use a scenario to illustrate my query : A digital PCB has some pockets of power and ground area fills with minimum trace width/clearance of say 6mil/6mil (0.15mm/0.15mm) and power trace width of 50mil. During bare board inspection (Class 3 requirement), one of the power trace that run along side of the ground fill, has an excessive copper protrusion that reduce the physical conductor to conductor clearance by 60%. Based on the IPC-A-600, it has violate the conductor to conductor clearance. However, the argument kick-in that it is not a violation and can be acceptable because the remaining clearance of 40% is much larger than the electrical clearance stated in IPC-2221 for that application. Now, how should this be resolved? Thanks and Regards, ~ Wee Mei ~ ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [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.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [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.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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For more information please contact helpdesk at x2960 or [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.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------