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December 1997

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Wed, 24 Dec 1997 09:06:31 -0700
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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
> >
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