SMD techniques

[PigPOg]

Hi, can anyone help please?

I have to migrate a number of designs from PTH to Surface mount. Can
anyone suggest a concise book or on-line resource that can answer
questions such as: -

Do I put mixed (PTH and SMD) components on the same side of the PCB or
on opposite sides and what are the associated merits/disadvantages?

and...

When generating the solder-paste mask what alignment marks do PCB
manufacturers generally require?

These are but two of many questions I have. I'd be most grateful for
any suggestions/advice.

Cheers,
Simon

 

[[email protected]]

Life is easiest if you put both sorts of components on the same side of
the board - putting SMD components on the track side the board means
that they have to be glued down before the board can be reflow soldered
- it isn't a big deal, but ti is an extra operation.

Solder-paste masks work the same way as every other mask - you don't
need special alignment masks (at least not anywhere I've worked).

The printed circuit board house that makes your boards should be able
to tell you all about this sort of stuff.

 

[PigPOg]

Life is easiest if you put both sorts of components on the same side of
the board - putting SMD components on the track side the board means
that they have to be glued down before the board can be reflow soldered
- it isn't a big deal, but ti is an extra operation.

Solder-paste masks work the same way as every other mask - you don't
need special alignment masks (at least not anywhere I've worked).

The printed circuit board house that makes your boards should be able
to tell you all about this sort of stuff.

Thanks for the info Bill.

Simon

 

[Fred Bartoli]

Life is easiest if you put both sorts of components on the same side of
the board - putting SMD components on the track side the board means
that they have to be glued down before the board can be reflow soldered
- it isn't a big deal, but ti is an extra operation.

Sure, but on the other side :

Having both components variety on the same side requires 2 additional
operations:
- solder past screening
- oven reflow
that are not necessary if the SMD components are soldered along with the TH
ones.


If _all_ the components can withstand wave soldering the most economical way
would be SMD on track side, and just one soldering pass.

 

[Apparatus]

I usually put SMT debouncing caps on the bottom of the board and
everything else on top. I'm a hobbyist though -- not sure how well this
works in mass production.

Be sure to put thermal reliefs on the power pins of the SMT pads,
similar to through-hole thermal relief. On my first board I had some
bad solder joints due to not putting these in.

Chris