Double-sided SMD PCB assembly

I know some of you guys have been experimenting with baking PCBs in ovens and other techniques. I’m curious about ideas on how to do this if the PCB has components that have to be attached to both sides. Are there options other than baking one side and hand soldering the other side?

Michael, how does your mechanical assembly line do this?

My guess is -

1.Apply Solder paste to first side and also use epoxy to glue the parts to the board
2.Place the components on the pick and place machine
4.Apply solder paste to the second side, expoxy can be avoided
5.Place the components
4.Reflow, the components on the bottom side may reflow but the expoxy will prevent them from falling off

Hand soldering will be used for DIP headers / sockets / jacks

@ Rajesh - that would certainly work. Are pick & place machines capable to also applying epoxy? I’m curious about how this is done by the big boys.

Another thought I had was the possibility of solders that melted at different temps. You could use a higher temp solder on the first side then flip it and cook again using a lower temp solder on the other side. I don’t recall any temp options in solders I’ve used but they must exist.

I bake one side, remove board.

Apply paste and components to the other side, and then bake again.

The previous side never falls off or anything.

Its pretty straightforward.

Have seen the video @ Mike posted before and still puzzled by why…
As @ BrightIdea has said generally no real issue doing the double bake without glue.
AFAIK you only need to glue fairly heavy parts - even when solder is flowing it is surprisingly tacky.

@ BrightIdea - That’s what I was really hoping to hear :slight_smile:

@ ianlee74 - Basically when you layout a board you keep all the heavy parts on one side and you reflow that side last. Plus once the solder paste has melted it takes a little more heat to reflow again and reflow ovens with bottom heat you can lower the temperature.

Excellent. Thanks, Michael.

Just a dabbler :wink: