Our specification is 0.010"/ inch. Like everyone else, our assembly sites and subcontractors experience the yield problems associated with warpage in the 0.005"-0.010" range. We work on the product design and manufacturing process to keep this impact to a minimum. I would prefer to leave the specification where it is and work the product and process issues than to tighten our specification, throw the issue at the PCB manufacturer and invite cost adders. Kelly Kovalovsky IBM Printed Circuit Solutions Engineer Email: [log in to unmask] Phone 607-757-4595, FAX 607-757-4621 [log in to unmask] on 02-19-98 06:48:51 AM Please respond to [log in to unmask] @ internet To: [log in to unmask] @ internet cc: Subject: Re: [TN] PCB warpage -Reply Matthew, IPC 275 specs out a multilayer .060" thick board as having a flatness requirement of 1% which equates to .010" / inch. Most of the time we receive boards that are well within the spec and we process them with no difficulty. When an occasional lot of boards are received that are on the high side of the spec we experience all the problems you described. Do you specify a tighter tolerance with your pwb shop. Does this tighter spec cause an increase in pwb cost. ( According to IPC to reduce the spec to .5% or .005" / inch reduces yields. I am curious as to what you and the majority of the industry is specifying. Thanks, Dan Shea Sr. Manufacturing Engineer The Foxboro Company Tel # 508-549-2410 Fax # 508-549-4379 Email: [log in to unmask] -----Original Message----- From: Matthew Park [SMTP:[log in to unmask]] Sent: Wednesday, February 18, 1998 6:53 PM To: [log in to unmask] Subject: Re: [TN] PCB warpage -Reply JIm, By the look of your message, you must be a quality eng/mgr or sales eng/mgr. No harm if i am wrong. Qual/'sales eng/mgr's usually like to go by the book and process/mfg eng's like to go by what work and what not work. To get to my points, IPC-275 Bow & Twist spec should be in a permanent storage. Boards that are closer to 0.01"/inch spec causes some problems in smt manufacuring and th wavesolding. They introduces printing registration inaccuracies, uneven solderpaste depositions and solderpaste skips. They go thru bumping rides during p/p placement cycles and off-placements of plcc's, qfp's and bga's are visible. They wont transfer thru edge conveyors without an operator assistence. Some chip components get disloged due to the springness of boards and slight vibrations. They cause more open solder joints. They allow flooding of solder on comp side during wavesoldering and prevents solder wetting on the highest area of warped boards. It becomes more important to have flat boards with advancement of finer qfp's and bga's. Bow & Twist spec of 0.002"/inch or less is better suitable for SMT assy. I know a lot of board fab shops won't guarantee with hasl boards. regards Matthew Park Automation Engineer NII Norsat International Inc. >>> Jim Mathis <[log in to unmask]> February 18, 1998 2:27 pm >>> I spec'd out .01"/inch, also, which used to be the spec. IPC-275 section 5.2.5.2 now specs Bow & Twist in terms of percentages. If you don't have a copy of IPC-275, let me know and I'll fax you the appropriate pages. ################################################################ 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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For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################