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I just started a design where I will be placeing smt parts o... - Feb 10, 2007 by jmabie

You're correct. So, you're thinking about putting the PTH p... - Feb 11, 2007 by davef

No, 50 parts on one side and 4 SOIC leds on the other. The L... - Feb 11, 2007 by

From what I see, you have a couple of options... 1. Hand... - Feb 12, 2007 by robgd3

Don't count out a wave pallet. if the led's are not an extre... - Feb 12, 2007 by pcbatech

Blob some peelable solder mask on the LEDs. They'll hold th... - Feb 12, 2007 by Real Chunks

just another problem with that smt stuff. think thru hole b... - Feb 21, 2007 by WaveMasterLarry

Thank you ... - Feb 21, 2007 by

They do make smt leds that mount topside over a hole and shi... - Mar 02, 2007 by

Rohm make them & call them Backfires: ... - Mar 12, 2007 by Rob

jmabie

#47499

SMT | 10 February, 2007

I just started a design where I will be placeing smt parts on both side of PCB. 50 parts on top side ranging from 0602 to SOIC8 and 4 SOIC LED's on bottom. How can I assemble with parts on both sides ? I have P&P,stensil printer, relfow and solder wave equipment. no glue dispenser. I ussually do smt P&P then reflow followed by wave solder of TH parts. One other issue, the 4 LED's cannot run through wave since they are on bottom side.

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davef

#47514

SMT | 11 February, 2007

You're correct. So, you're thinking about putting the PTH parts on the same side as the SOIC LED, making the top into the bottom, right?

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jerry

#47522

SMT | 11 February, 2007

No, 50 parts on one side and 4 SOIC leds on the other. The LEDs cannot go through the wave so I need to mask them off or cover them up to protect them during the wave.

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robgd3

#47558

SMT | 12 February, 2007

From what I see, you have a couple of options...

1. Hand solder the secondary side LED's. This is only a good option if you're going to be at low-ish volumes. Higher volumes tend to necessitate more automation to reduce production costs. However, even at higher volumes, depending on the costs of hand-soldering, it might be the most economical solution...hand-soldering once generally costs less than extra tooling, or replacing damaged parts.

2. Selective wave solder. If you've got enough clearances on the secondary side between the pads of your SMT devices, you can buy a selective solder fixture to place the board in, and only wave solder the through-hole components. This is an excellent volume solution, if your design allows it. I'm not sure of the recommended clearances, but it's either been discussed in these forums previously, or someone out there knows them and will chime in with them.

3. Mask and wave. This has worked for me on a number of occasions. We use a liquid mask that generally provides enough protection to the parts to prevent thermal issues. This, of course, depends upon the thermal thresholds of the components. Assemble and reflow per normal; mask the secondary side components, assemble and wave through hole.

cheers ..rob

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pcbatech

#47563

SMT | 12 February, 2007

Don't count out a wave pallet. if the led's are not an extremely tall part a pallet might be just the thing for running something like this at a higher volume.

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Real Chunks

#47570

SMT | 12 February, 2007

Blob some peelable solder mask on the LEDs. They'll hold thru wave.

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WaveMasterLarry

#47888

SMT | 21 February, 2007

just another problem with that smt stuff. think thru hole baby!

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jerry