Hullabaloo!! Wally, I am with you all the way. Theoretical reasonings for siding with oblong lands are not same as practical results. There are no signifcant gains for using oblong lands. Both oblong and square lands provide a good soldering result. In fact, it is more of headache to generate oblong shapes and apply them for photoplotting as per your response. Some of statements " Oblong stencil openings provides better solder paste release" are theoretical and there is only less than 5% practical truth for that statement. Major deciding factors for good solder paste release are based upon: - rheology and condition of solder paste being printed - screen printing parameters such as separation speed - stencil opening wall - aspect ratio - underneath stencil wipe frequency There is no etched-in-stone rule that stencil opening shapes must be same as smt lands. Any shape and size are acceptable provided that it produces good soldering joints and fillets, and there are no process defects such as solder balls, solder bridges, solder paste skip etc... regards mpark NII, Norsat International Inc >>> "Wally Doeling (wallyd)" <[log in to unmask]> April 1, 1998 9:19 am >>> OK, but I disagree! We at Sequent use rectangular pads and do not see a problem with concentrating the solder at the joint. We do not require that the entire pad be covered with solder on the final product. This allows the assembly supplier to modify his solder stencil and make it oblong for better release of the paste. The solder deposit shape does the concentration of solder fillet along with the wettibility of the lead. What we see is that all of the solder flows to the solder joint and leaves very little on the unused portions of the pad. The advantage of routability with the oblong pad is not something that adds much to the design as routing on a grid and using 45 DEG. corners is not compatable with a round feature.... not a significant gain in my view. The biggest problem with a oblong pad is that it either has to be drawn with the CAD system (creates a large Gerber file) or has to be constructed as a complex flash by the photoplotting vendor. All of this for no gain in my view! We did a test of oblong pads with rectangular pads on the same design. When we received the board, we could almost not identify the two designs, as the square corner is rounded in the PCB etching process to a extent that it approaches the oblong. The question of pad shape vs stencil opening shape should be separated, and are different with most assembly houses. Many articles have been published about different opening shapes in stencils. All are a advantage in each assembly house under their processes. To think that the pad shape dictates the stencil opening is a bad basic assumption! Please give me some feedback on the above. I would like to hear your reasoning for your position.. [log in to unmask] -----Original Message----- From: Gary Ferrari [SMTP:[log in to unmask]] Sent: Tuesday, March 31, 1998 8:27 PM To: [log in to unmask] Subject: Re: [TN] oblong lands Marletta, It is preferred to have oblong lands to assist in concentrating the solder fillet around the component lead. The IPC-SM-782 indicates oblong as optional but should read preferred. Regards, Gary Ferrari Executive Director IPC Designers Council (860) 350-9300 Fax (860) 350-9309 [log in to unmask] >>> Marletta Tucker <[log in to unmask]> 03/31/98 03:13PM >>> What is the deciding factor on whether or not an SMD parts land is squared off or oblong? Could/should all SMD parts have oblong lands? @ @ @ Thanks, @ @ @ /// @ * Marletta Tucker @ @ > 1921 Hurd Dr. M/S 2-21 @@|\ _ Irving, Tx. 75038 @ | 972-518-7619 # [log in to unmask] We have enough youth, how about a fountain of SMART? The above views are my own, and do not represent those of Abbott Laboratories. ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. 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