MLP (Micro Leadframe Package)

2017/2/2 1:54:46

Hi: I'm looking for input from anyone who has experience assembling the MLP package on PCBs. We are experiencing solder opens after assembly, and I'm curious to see how others are processing these critters.

The part we are using is a Semtech SH3000 (microbuddy) It is 3mm by 3mm square with four solder contacts on each bottom side. Since there is no leads on this package, there is no standoff from the PCB. Because there is no standoff/gap under part, we do not run it down our SMT assembly lines which use water soluble solder pastes. Our customer does not want to use a no-clean assembly process for the whole PCB. I do not think that a water wash system would reliably clean the organic acids from the water soluable paste under the part. The solder connections are on the underside of the part only, and are not visable after processing. I am having difficulty X-raying the joints to verify them.

Our assembly process for this part is as follows:

1. Screen print solder paste on PCB(water soluble flux type) 2. Place SMT parts (except Microbuddy) 3. Reflow assembled PCB (convection reflow) 4. Clean PCBs in water wash system 5. Flux Microbuddy location with Kester TSF-6522(no-clean "tacky" type flux) 6. Hand place Microbuddy 7. Local reflow of solder using handheld hot air tool. (Haako 850)

My questions are: A. What assembly processes are others using to attach this part. B. What inspection methods are others using to verify solder connections? C. Are others using water soluble solder paste, and then water washing?