Dear Colleagues,
I am working with a new prototype product that is presenting some interesting problems. My Engineering Dept. has made some suggestions that I find a little odd. I am looking for some confirmation from fellow SMD personnel as to the soundness of these suggestions.
The suggestions include: 1st.
"Soldering and unsoldering is strongly recommended to be accomplished with a hot-air pencil, since it is practically impossible to cause thermal shock cracking using hot air pencils."
2nd.
"Post reflow rework processes will be different than in the past. Due to the size and nature of the component packaging, the PCB and the component both need to be heated to bring the solder joint to melting point, and allowing the removal, replacement or repair of the part.
Processes and tools that will only heat the component will result in some of the problems discussed about moisture sensitivity. Heat sources that directly heat the component (i.e. - soldering irons) can cause thermal shock.
The much preferred method is the so called �SMD rework station�, which heats the PCB from underneath, uses temperature controlled directed hot air to melt the solder at the joints, and a built in vacuum pick up to remove the component." And finally, and most worrisome,
"Add liquid flux to the solder paste post placement and prior to reflow."
The first two suggestions have merit but the final suggestion seems very strange to me. I realize that this has been a lengthy posting and I appreciate your time.
Thank You,
D.B.Davis
This message was posted the
Electronics Forum @
reply »