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SMT on Solderside For Thruhole board

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wuchy143

Member
Hi All,

I am designing a PCB which is like trying to fit 10lbs of potatoes in a 5lb bag.(I'm sure many can relate) I am opting to put some surface mount stuff(mainly 0805 R's and C's) on the solderside of the PCB.

There are not many of these components and was wondering if there were any methods of waving this board with the bottom components already installed on the PCB. Would "gooping" RTV over the surface mount parts help so they don't fall off? I would rather not design a fixture for something like this to make it waveable. There are not many components and just want to know if there are any crafty ways of dealing with it. I'd like to stay away from very expensive things.

Thanks
 

jbeng

Member
The usual assembly methods for this application are: A) deposit a droplet of adhesive on the pcb for each component using a needle equipped robot; or B) create a stencil and apply the adhesive to all the component locations on the entire side of the pcb at once. These operations are (obviously) performed prior to the smd pick and place and thru-hole insertion processes. The board is then wave soldered as normal.

Jeff
 

wuchy143

Member
How many copies do you need to make ?

The quantity of this order are only 10.(pretty small quantity but for us it isn't too small. Probably average for new designs)

The usual assembly methods for this application are: A) deposit a droplet of adhesive on the pcb for each component using a needle equipped robot; or B) create a stencil and apply the adhesive to all the component locations on the entire side of the pcb at once. These operations are (obviously) performed prior to the smd pick and place and thru-hole insertion processes. The board is then wave soldered as normal.

Jeff

Hi Jeff,
Thanks for the info. I like the idea of a stencil. That seems to make the most sense for someone by hand doing this type of work(it would be done by a human where I work). What type of "adhesive" do you recommend to use? There must be a spec I could look at to see if what I have in stock would work. Or I could look into what you recommend and buy that to try it out.

-mike
 
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jbeng

Member
I can't tell you any names of specific products because I haven't worked at the place (which used process "B") for nearly two years. They had an automated "squeegee" machine, which used the stencils, for each of their 4 SMT lines. Do a google search for "SMT adhesive" and I'm sure you'll get plenty of relevent results back for what you're looking for.

Jeff
 

wuchy143

Member
Jeff,

One last question. This may be obvious but just want to clarify. You are suggesting applying the SMT adhesive directly to the part when it is already installed on the PCB? Then putting it through wave solder for the thruhole parts.
 
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