Thanks. I moved the 9V track and removed the 5V track under U2.
One more important question before sending it to the manufacturer. (I have asked this before and @Rene_Poschl answered nicely, I just wanna be sure if I can do it with my equipment). There will be no soldermask between the pads of the U2. Is that a problem since I am hand soldering with chisel tip? I solder SMD chips before with the dragging technique (just drag the tip across the pads), but is this possible if there is no soldermask in between? I also have a flux pen.
I hand soldered a similar pcb a few months ago.
I donât really use the drag method though. (At least not in the way that you put a lot of solder over all pins and wig the excess away afterwards.)
I put very little solder onto the tip and solder each pin separately under a microscope.
The microscope helps a lot. But if you have a good magnifying glass it might already be enough. (I use 20x magnification setting on the microscope while soldering. I can set it to 40x magnification but i never used this setting.)
I usually just manually spread a little solder paste on the pads, mount the parts, and pop it into the toaster oven. Put an oven thermometer in there with it and manually control the profile. Works every time although I do occasionally get the odd tombstone.
Solder doesnât stick much to plain FR4 much more than solder resist, in my experience. Iâve also used drag technique, and the lack of soldermask doesnât seem to be a problem. Either way I get a few blobs that need to be removed with solder braid. I donât flood fill with solder though - I donât think that is a good way.
One thing I try do is ensure that tracks enter the IC pads straight rather than an angle, and also avoid running tracks near the pads. Sometimes the soldermask exposes a bit of a nearby track, which risks shorts. Also if you are doing a board that might be âexperimentalâ, avoid running tracks under components, as they are very difficult to rework.
Here I would move the 5V track away from the GND pad a bit.
Hand-soldering SMD components is an area where there is more âartâ than âscienceâ, and each artisan develops his preferred style, methods, and techniques. When doing an entire board I use solder paste dispensed from a plastic syringe, and an electric skillet (purchased quite inexpensively at a second-hand shop) as my âreflow ovenâ. I think itâs documented in old posts of mine - try searching with âskilletâ as a keyword. There are also several good internet pages on the topic.
For rework, repair, and touch-up after reflow I use a fine conical tip in my soldering iron. The toolmakerâs microscope (similar to the one already mentioned) is definitely helpful. I think the one I use cost my employer about US$200 and has 10X and 20X magnification; the lower magnification is quite adequate. Having said that, unless I have a large volume of SMT work at hand, I usually get by with just a decent-quality desk-mounted magnifying light.
When adding SMT components to an assembled board, the combination of soldering iron (with the fine conical tip) and solder paste works well for me. My attempts at using the âdrag techniqueâ have never been satisfying to me. Perhaps that would change with extensive practice. My tray of soldering tools includes the finest gauge, rosin-core, wire solder I can obtain; some wooden toothpicks; stainless dental probes; cotton swabs; pure isopropyl alcohol (not the 70% stuff from the drugstore); and fine-braid solder wick.
