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Cost effective double-sided SMT + thru-hole

Stuart Adams


Cost effective double-sided SMT + thru-hole | 12 May, 2000

Is there a cost effective way to do assembly of boards with SMT components on boths sides as well as thru-hole parts ??

(Is there a solution other than hand-soldering the thru-hole parts after SMT reflow of both sides ???)

Thanks, Stuart

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M Cox


Re: Cost effective double-sided SMT + thru-hole | 12 May, 2000

There are a variety of options without knowing what kind of components are on the bottom side (C's and R's 0805 or 0603 or 0402) you are talking about consider the following Option 1 If bottom side has only Caps, resistors and/or Soic's then... Top side, A)Paste B)place C) reflow Then on the bottom side (not recommended for 0402 and smaller) A) dispense (or screen print) adhesive B) place C) cure the adhesive (sub reflow temp). Then wave solder the through hole parts and the glued down SMT parts.

Option 2 If you have PLCC's, fine pitch parts, or <0402 parts on the bottom then you Could... Reflow both sides then use a selective wave fixture (used to mask the SMT parts). This option assumes you have enough room between the PTH parts and the SMT parts to form a gasket with the fixture.

Option 3 Reflow both sides and then using liquid mask, mask the bottom side SMT parts.

Or a combination of all three depending on the component layout and MIX.

OK now if you have thru-hole parts mounted on both sides then a Mini solder wave (dipper) may help with those parts.

But before you do any of the above go slap you're PCB designer (it will make you feel better) and do some DFM and/or DFT work up front.

Mike C

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Re: Cost effective double-sided SMT + thru-hole | 15 May, 2000

You should also consider intrusive reflow (aka pin in hole relow� but be aware of the thermal possibilities of your through hole components and ask support from a stencil supplier that has done this before.

Hope this helps,


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