On 23 December, Eric wrote:


>Hi Barry, In response to your question regarding epoxy dotting bottom =
>side SMT components and then wave soldering or using pallets or =
>carriers. Let me ask you this, How many additional steps are you adding =
>to the process when you use the epoxy dot method ? How much additional =
>time does it take to epoxy " ALL"  The smt components? Is the boards =
>bottom side heavely populated ? I am asked this question quite often =
>Barry, I am a design mfg of selective solder and smt pallets. The =
>question most commonly asked is " How can pallets benifit my process, =
>This is only one of the areas pallets can compliment the throughput of a =
>production line. We have not even scratched the surface!! E-mail me or =
>call if I can anser any question you may have regarding SMT pallets or =
>Wave solder pallets at [log in to unmask] or call toll free at =
>1-800-725-5388 =20



>>Subject: WAVE SOLDER FIXTURE
>>Hi Technet,


>>I need some information about wave solder fixtures. Is it better to glue
>>SMT parts on the bottom of the board and wave solder them along with the
>>through hole parts or to solder all SMT first, and then attach a solder
>>fixture to cover the SMT, and then wave solder through hole.


>>Thanks for any help.

>>Barry Darnell
>>(864)627-8800 Ext. 231
>>[log in to unmask]
>>Computer Dynamics, Inc.
>>Printed Circuit Board Designer


Barry,

   Believe me, what you want to do, seeing how you design the PCB's, is to 
follow the guidelines that are documented quite extensively of the proper way to
layout the bottomside for epoxy/wave. In fact, if you can possibly do it, keep 
all yer' surface mount on ONE SIDE! (that goes without saying the topside of 
course!) 

   Sure, wave soldering bottomside surface mount is done all the time, BUT, I'd 
bet ya' a dollar to a donut that if a Process Engineer had a choice between 
building a single-side SMT board or a double-side SMT board, he'd likely choose 
single-side SMT anyday! (I can't speak for those "kinky" engineers who like pain
and misery though...)

   To me, having to use a pallet is because the board hasn't been designed to be
run without one with the equipment being used to build it...the goal should be 
to run without a pallet if you can help it. 

   That's where it helps if the designer has a good understanding of the machine
specifications and the capabilities where the product will be built in order to 
design a product that is efficiently and easily built...

          DFM...Design for Manufacturability, what a novel concept huh?

   Why, you may ask? Why don't you want to use pallets? Because if you use one, 
you can just about rule out trying to implement any C.F.M. methods (Continuous 
Flow Manufacturing) unless you plan on buying hundreds of pallets...(that would 
make Eric happy I bet!). 

   In the contract assembly environment, most customers are pretty darned cost 
conscious when it comes to the N.R.E. (Non re-occuring expenses), and you can't 
very well absorb the cost of the fixtures (anywhere from $100-300 each depending
on the complexity) and still expect to be competive and turn a profit...margins 
are pretty slim as it is, ask anyone who's in contract assembly.

   So if ya' ask me, NO PALLETS if ya' can help it at all. If not...oh well, I'm
sure Eric at $P PRECI$ION will sure help ya' out...
                                                          __\/__
                                                      .  / ^  _ \  .
                                                      |\| (o)(o) |/|
                                            #------.OOOo----oo----oOOO.-----#
                                            #          Steve Gregory        #
                                            #      SMT Process Engineer     #
                                            #  The SMT Centre Incorporated  #
                                            #   [log in to unmask]   #
                                            #________________Oooo.__________#
                                                      .oooO  (   )
                                                      (   )   ) /
                                                       \ (   (_/
                                                        \_)
  

 

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