The bar seems to raise itself at times, after the sixth single malt. As for the floor lowering, five suffice before it moves all over the place. Brian On 02/05/2011 20:30, Whittaker, Dewey (EHCOE) wrote: > Even with the best intent on your part to justifiably "raise the bar", > this is a potentially false perception due to your supply chain > implementing a "lowering of the floor" strategy. > This is on a par with me trying to explain how clever and witty > "Deweyisms" are to someone when English is not their native language. > Dewey > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Brooks, Bill > Sent: Monday, May 02, 2011 9:52 AM > To: [log in to unmask] > Subject: Re: [TN] "The Curse of IPC-A-610 and IPC-J-STD-001" - opinion > piece by James Smith > > I have been 'listening' to this thread and it kind of struck a nerve. > 'Designing to minimums' or to 'just meet a spec'. Not just meeting > minimums on the low side of the 'bell curve'... but DESIGNING to the > minimums... I have seen this happen a number of times where someone > reads a MIN. requirement spec and then designs to it. WRONG! Only > inexperienced folks who don't understand tolerances' do this sort of > thing. > When we train PCB designers we drill it into their heads... don't forget > the tolerances. Worst case means WORST case....even after everything > else has gone to the extreme limits... If you want reliability you need > to design in some 'de-rating' into your tolerance calculations... give > yourself some 'head room' for things to go wrong... a good design will > still fly even if everything else has failed... by design. It doesn't > happen by accident. > > I believe board manufacturers use the IPC standards as a way to commonly > agree what minimum acceptance they can 'get away with' process-wise... > but if their customers aren't designing their products to achieve the > results needed then they are going to just make a lot of scrap. > Tolerances statistically will get you every time! > > Maybe what this guy James Smith was 'trying' to say is, (even though he > did it badly), that he needs to 'raise the bar' of the design higher > because he is seeing the quality of the boards coming in and they aren't > acceptable to him or his company... even though they are meeting the IPC > standards. Maybe he needs to hold his vendors to a 'higher standard' or > or rather a higher design requirement... ??? Typically when the min > requirements stated in an IPC standard are not acceptable to us for our > product, we put an exclusion or acception in the notes of the drawing to > say how our requirements differ from the spec. IPC specs are a > baseline... from there you can design in the higher quality through your > DESIGN requirements. DON'T design to the minimums... BAD DOG... TIME > OUT... NO COOKIE... > Frankly, James is blaming the wrong guys... it's not the IPC > standards... it the design and quality teams not setting the > requirements high enough for his product. > > Imho :) > > > Best regards, > > > Bill Brooks | Datron World Communications, Inc. > PCB Designer/Engineer | Office: 760-602-7004| Fax: 760-597-3777 | > [log in to unmask] > 3055 Enterprise Court, Vista, CA 92081 | www.dtwc.com > > Performance You Require. Value You ExpectTM > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Woolley, Mark D. > (Mark) > Sent: Monday, May 02, 2011 7:16 AM > To: [log in to unmask] > Subject: Re: [TN] "The Curse of IPC-A-610 and IPC-J-STD-001" - opinion > piece by James Smith > > Sorry, Let me try again. (I don't know what happened the last time.) > > Being a slave to "Standards" is not where we should be as an industry. > The "standards" are, in reality, minimum acceptable criteria. I often > hear manufacturers state that they build to a standard or their product > meets the "standards." > > However, as I inspect these products per the same standards (mostly > IPC-A-600 and IPC-A-610), I see that while the product might meet the > "Standards" it was manufactured along the minimum edge of acceptability > per the standard. > > An example: Visible, opaque particulates embedded in the solder mask > might meet the IPC-A-610 standard if they do not encroach on certain > areas of the PWB. But what does finding multiple occurrences of > particulates in the solder mask mean in terms of the PWB manufacturing > quality? Unless you are dealing with military classes, in mass > production a close visual inspection can only be performed on a limited > number of units. If those units barely meet the standard what does that > indicate about the remainder? (How many particulates might be embedded > within the PWB layers where they are not readily visible? And of these > how many could eventually cause a short?) > > Meeting the Standards is not sufficient to build a reliable product. > The standards must always remain as the minimum acceptable criteria not > as the expected mean or median product. > > The IPC committees put long hours into each specification to clarify > points and make the items as understandable as possible. IPC-A-610E > (and later revisions) is a great asset. Pictures showing both the good > and the bad are presented. But never is it stated in the specification > (that I have read) that a process that consistently produces products at > the edge of acceptability (per the standard) is acceptable to industry. > > Having said that I must agree with Brian's statement: > > "In short, Standards, used appropriately, can help, as far as possible, > to perfect reliability for a given application. Used inappropriately, > they can drive up costs dramatically ..." > > There needs to be common sense in the application of the standards, both > from a user and a manufacturer point of view. Customers' don't want > manufacturers to hide behind the "Standards' Wall" when confronted with > issues with their products. And the products should be manufactured in > a manner that places only the smallest percentage, (ideally none) of > products below these limits. > > > > mark > Mark Woolley |PTRL Laboratory | Avaya | 1300 West 120th Ave | > Westminster, CO 80234 USA | > Voice (Lab): (303) 538-2166 | email: [log in to unmask] | > > > ---- > > ______________________________________________________________________ > 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 16.0 > 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 > 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 16.0 > 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 > 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 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------