Hi Paul, Could you send me a copy as well? My fax number is (303)492-3498. Best regards, Yuan Li Research Associate Mechanical Engineering University of Colorado On Wed, 24 Dec 1997, Paul Klasek wrote: > Hi Richard > > Could not agree more with Ed ; = feel guilty & out of time . > What I can tell you as we go through TH > SM conversion right now on the > overall process you save 15-20% , that is materials, directs, OHs , etc. > I did very detailed study for cost benefits validations, inclusive the > subcontract options ( TH inhouse x SM inhouse x SM contract ) . > I think you go through the same . > Let me know if that is so, I'll try to generalise my ( confidential ) > spreadsheet over Holidays for outside use . > Let me know the fax No. too , I have some old papers and no scanner . > > See you [www.resmed.com] Paul > > >---------- > >From: Ed Holton[SMTP:[log in to unmask]] > >Sent: Wednesday, December 24, 1997 6:14 AM > >To: [log in to unmask] > >Subject: Re: [TN] Cost comparisons TH vs SMT > > > >Richard > > > >I understand your frustration about having your question not answered, as > >it has also happened to me in the past. But don't give up the fight, you > >should be applauded for asking the question. That is a much better > >attitude then never asking. . . > > > >I do not have any hard numbers for you about thru-hole vs SMT components, > >but your design should not be based just on component cost alone. There > >are numerous intangibles that must be considered: > > > >Placement: SMT has the capability of 6 sigma quality for placement while > >TH is approximately 3 sigma. For example, most TH machines will have 3 > >mis-insertions out of a thousand. SMT is significantly better. You need > >to consider the quality improvements of SMT over TH and the increased > >efficiency. > > > >Optimization of process. Design your board for all SMT and you only need a > >SMT line. Add in TH and now you need TH machines and a wave solder. > > > >Efficiency/speed: I have yet to see a TH machine reach 40K plus placements > >an hour. > > > >Soldering: SMT reflow is capable of higher quality levels than wave > >soldering (however I must brag that I am below 100 ppm with my wave solder > >process! Thank you to Bob Willis, Ray Rua, John Maxwell and SEHO who have > >helped me achieve this) > > > >In my opinion, it is better to spend a few more cents for all SMT and > >increase first time yields and throughput rather than some of the known > >fallout due to TH and wave soldering. However, keep reading because there > >are many more caveats to consider. (I work in automotive electronics where > >every cent counts, however I firmly believe that spending more on the > >components will save on rework/repair cost. These are hidden costs, that > >the customer never sees except when accounting calculates the overhead. > >Have gone many rounds on this with accounting) > > > >Component cost. Many SMD components are cheaper than TH, especially chip > >capacitors and resistors. But there are many high voltage devices and > >connectors that are still less expensive as TH. However, I have seen the > >cost of many components drop such that when the program was first > >developed, TH was cheaper, but within 3 years, the SM components were a > >better deal. Consider the future of components when designing. > > > >DIP components. While a DIP package may be more cost effective than an > >SOIC, the placement issues between the two of them, plus the need for a DIP > >inserter as a special piece of equipment vs. the SMD placement machines > >that place chips to quads, we eliminated all DIP components from future > >designs. > > > >Look at commonization of components to get better volume discounts, what > >components are used in design today at your facility? > > > >Optimization of process: Some components are not available in SMT packages > >and you are forced to use TH. If this is the case, consider using more of > >the same kind of TH components to efficiently use the TH machine (this > >usually happens with radial components) and balance the process time > >between the two machines. > > > >The list goes on and on. Basically, don't decide the design just on the > >cost of the components, you will get burned and your M.E.'s will hate you > >(haha). Many other factors should drive the decision. At a previous > >employer, i started to develop design guide lines based on the > >manufacturing capability of the production floor. As a designer, you > >should know what your capabilities are, and what the ME group has planned > >in the future. > > > >Here is a sample for you. I proposed to our designers/engineers when > >designing a new board: > >1. make it all top side SMT. (one process and you are done) > >2. make it top side SMT with thru-hole soldered using paste in hole > >technique. (new process development) > >3. make it top and bottom SMT reflow (same amount of equipment required as > >in number 1, but double the assembly time) > > > >Here is where it gets tricky: > >if significant TH is required you have three options: > >4A. reflow SMD, insert TH and wave solder or selective solder the TH > >joints > >4B. Adhesive attach SMD to bottomside (including SOIC's and Quads), insert > >TH and wave solder the whole thing (but your wave solder better be in > >control, pad design, etc.)(This might allow use of CEM1 as opposed to FR4, > >what a cost savings!!) > > > >5. topside reflow, TH, bottomside adhesive and wave solder the whole thing > >(yes, these are all variations on type I, II, and III) > > > >BUT, after all the above have been considered, the whole group needs to > >discuss the best design, based on efficiency, quality, through-put, > >component cost, etc. > > > >So, I hope this sheds some light on your issue. No hard numbers, but some > >other things to consider. > > > >Ed Holton > >Hella Electronics > > > >############################################################## > >TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional > >information. > >For the technical support contact Dmitriy Sklyar at [log in to unmask] or > >847-509-9700 ext.311 > >############################################################## > > > > ############################################################## > TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional information. > For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 > ############################################################## > ############################################################## TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional information. 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