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Topic: Double Sided SMD (Read 4 times) previous topic - next topic

KirAsh4

Oct 10, 2012, 08:36 am Last Edit: Oct 10, 2012, 08:44 am by KirAsh4 Reason: 1
Has anyone here done their own double sided SMT work?  I've only ever done single sides with the skillet reflow method.  Obviously this wouldn't work for double sided.  So, I'm looking for ways to accomplish this.  Any particular type of oven I should start looking for?  Is it always done with epoxy on the parts that end up on the bottom on the second reflow?  Does it even have to be two reflows, or is there a way to get it all done in one pass?  Comments, suggestions, baseball bat ...

kg4wsv

I use hot air (Hakko 800 series) and have placed SMT stuff on both sides.  One wasn't really a challenge as the components that required more heat weren't back to back on the board.

In my typical double sided SMT situation, I'll have a few small caps and resistors on the bottom of the board, with most of the components on the top.  The small components don't fall off; I guess they never get hot enough to melt, or they are held by surface tension of the solder.

My boards are small, with few components on the bottom.  YMMV.

-j

CrossRoads

I have a smll 328 board with 3-4 Rs & Cs on the bottom, just a touch of an iron to install them.
Don't know what kind of glue is used to do an oven reflow for both sides at the same time if that's the way it is done.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

KirAsh4

Hrm.  The board I'm thinking of making is about 3cm x 3cm in size.  On one side it has a SOP14 IC, several 0603 resistor and caps, a SOD23 zener, and some SOT23 NPNs.  On the other side it has 3 5050 SMD LEDs and one 0805 resistor.  Hand soldering the 5050s will be rather difficult because of their proximity to each other.  And the last time I tried hot air for those, I ended up with lots of failures.

I can do a skillet reflow on either side just fine.  I just don't know how can I do both sides.  If I do the one side with the most components, what's a good way to do the other side with the 5050s?  I don't think it's safe to place the boards back on the skillet with the SMD parts down (touching the hot plate.)  Thermal shock and all.  And if I raise it off of the plate, even by a few millimeters, it might take longer to heat up and reflow the top and by then the bottom parts would be rewetted again ... I think.

CrossRoads

Kapton tape them in place & do both sides at once?
Its good to 500F.
Not to exceed temp during flow is 250C, 482F.
Guess question woul dbe hot to apply the tape without squeezing the solder paste out of place.
Perhaps pre-tin the bottom, then flux & tape the parts on while also placing the top side new?

Or get some of the glue that's used on the tape.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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