After The Net

OK, this time, more things and fewer words. Very unlike me, I know. Let’s declare a theme for most of these items–soldering. If that’s not interesting to you, I’ve saved you some reading! Do at least have a look at the office chair wheels towards the end of the list, though, if you have a wheeled chair in your shack or home office. There, more reading avoided if not!

• Organizer boxes for small parts. I have lots of small electronic parts. For some, I use the slide-out drawer-type storage compartments that mount on a wall. And I have quite a few of these, but for certain items like small SMD surface-mount “chip” parts, I need smaller compartments that I can move around, and that do not spill the little parts if dropped or turned upside down. I bought a couple of these recently, and they fit the bill nicely. They won’t spill things, can be easily re-configured for larger or smaller compartments, and generally look to be good quality for the price, which is $10.99 each. By the way, they are the soft-feeling plastic, not the hard, brittle type. Since they are “just” plastic, I would avoid putting anything in them that could be damaged by static electricity.

• If you do much soldering or building, or need to repair soldered pc boards on occasion, here is a very inexpensive hot-air soldering and rework station. Price is an unbeatable $75.99 for everything, including various sizes of hot air tips. If you’ve never used hot air for de-soldering an SMD part, you’re in for a treat. Hot air can also be used to solder, if you’re careful. Be sure to keep the temperature high, the air tip small, and the airflow low. You don’t want to blow other components out of place. Been there, done that. It’s not rocket science, though. Just be aware of that little issue. Doing SMD repairs with this gadget (along with the liquid flux mentioned next) will save your sanity.

• If you’ve ever done any soldering, this may not be something you’ve had any experience with before. That’s because many people don’t understand the need for soldering flux, but I swear by this little bottle. It’s helped me do so many otherwise difficult (or semi-impossible) soldering jobs with SMD components. Without going into a chemistry lecture, let me simply say that it makes the parts you want to solder together more attractive to solder. It gets rid of the surface tension or oxide that sometimes causes the solder you’re applying to ball up or just drop off the part, rather than melting nicely to it. For SMD parts, I literally drown the little chips in this flux (you can drown them with a single drop), and they just magically adhere to whatever you’re trying to get them to stick to. It does this by its mildly-acidic nature, stripping oxide off of copper or tin pads or wires, and then keeping oxide-causing air away while you solder the parts. Another bit of goodness is that this is genuine Kester soldering flux. Kester has always been a big name in solder and soldering chemicals. This little 2 oz bottle is $13.18 with the usual free shipping, and it will likely last you the rest of your life, unless you do as much soldering as I do. I’m on my second bottle. Highly recommended for soldering even big parts together, and the little needle-like applicator helps you by doling it out at just a drop at a time. Many times you’ll only need one drop.

• After you’ve soldered something, especially if you used flux, this next item is a nice-to-have near your soldering station. It’s an alcohol pump dispenser for $9.90. You grab a cotton swab or Q-Tip, tap the top of the dispenser with it, and a little bit of alcohol soaks it. You can then swab the solder joint or pc board to get rid of flux or just for general cleaning. This is almost mandatory to do if you are using high-impedance (and static-sensitive) devices, such as MOSFET’s, CMOS microprocessors, etc. The left-over flux can attract dirt and dust, and eventually form a low-resistance short between two points you didn’t intended to have shorted to each other. This scenario is most likely when you are working on a printed circuit board, rather than freehand soldering of, say, two wires together. At work, we have one of these pumps and some cotton-tipped sticks at each soldering station. Good stuff, and you avoid having a constant alcohol-ish smell in the lab.

• Keeping with the soldering theme, you should clean the tip of your soldering iron often, ideally each time you solder a single joint or part. If that seems excessive or OCD to you, let me assure you that it’s not. As soon as you finish soldering a connection, the remaining solder or metal on the tip of your iron starts to oxidize. That layer of oxide will act as an insulator when you go to solder your next part, making it seem like your iron temperature has gone down, often significantly. It also makes it very hard to tin your tip with a little solder, which you should do before soldering a new connection. To keep oxidation of the tip from happening, many people, including me sometimes, use a wet sponge. Wiping the tip with a damp sponge helps keep the tip nice and shiny, but also wipes away any solder still remaining, and that isn’t always what you want. This next item solves the tip preparation problem by giving you a small, bottlecap-sized container of tin and ammonia for only $6.35. I hot-melt glued mine to my soldering iron holder, and I just rub the tip on it briefly before starting a new solder joint. It’s texture is hard, but just a bit of it melts on to your iron with each application. It cleans the tip of oxide, and adds back a little tin to “tin” your iron each time. As you probably know, solder is mostly made of tin, lead, and a little flux. At least, it used to be that solder was tin/lead. Now we have lead-free solder, which I can tell you from experience is mostly horrible stuff. It has a wetting (adhesion) problem. Thank goodness you can still buy the good ol’ 60/40 or 63/37 tin/lead solder. The link is for a one-pound roll of the best solder on the planet for just $27.28. A pound will last you a long time. Regarding the worldwide lead-free rules, it’s true that we have to use it in electronics manufacturing, yes, but not for hobby or lab use, thankfully. Wash your hands after a soldering session, though.

• Speaking of soldering, there are other ways to hold things in place. In the past I’ve used the white foam double-stick tape for mounting various small objects, as I’m sure you probably have. I’ve always thought that there should be something better. Something with more grip. Something permanent. And then I noticed that our little WiFi modules were mounted to some TV chassis with this interesting black tape that really stuck them in place. They were definitely not going anywhere with this tape on them. Trust 3M to have developed Scotch VHB tape for this purpose. VHB stands for Very High Bond, I think. You can stick just about anything to just about anything else! Here is a 1 inch by 15 foot roll of it for $17.99. Very good stuff. It has some thickness to it like the white foam stuff. Just make sure you really want to stick something in place before you, well, stick it in place. Makes the white foam tape look sad and anemic.

• You might find this next one a bit strange, considering the electronics theme we’re on, but let’s say that this might improve your soldering by giving you better mobility and keeping static electricity down a bit. I’m talking about replacing the little plastic casters on your wheeled office chair with these very useful replacement urethane wheels made for office chairs. They are $38.95 and worth it. They work way better on many carpets than those little hard plastic casters, and eliminate the need for those awful plastic carpet protectors. Here in the mountains of Utah, carpet protectors are HUGE static electricity generators. I can sit down on one, move a foot or roll the chair a bit, and draw a 1/4″ spark off of anything I touch. You can actually get anti-static carpet mats, but they cost 2X-3X or more. Anyway, these wheels roll way easier, don’t get fouled up in things as much, and have way less rolling resistance. They are made to fit the (almost) universal rod and lock ring found on most office chairs. And there are 5 of them, which I didn’t realize is a very common number of legs on wheeled office chairs. I popped out my old ones and put these in with no tools in under 5 minutes. Whee! Now I can really roll–I love them! The only downside, and it’s minor, is that they make the chair seat about 1″ taller. If you have your chair lowered all the way down like I do, that might be an issue. It actually is for me. I’m 6’1″ tall, but I’m about 6’7″ from the waist up (and I’m only a 31″ inseam–I think they call it being over-square or something). So I sit tall, so to speak. People in my office who occupy a conference room after me always know where Dave sat–their eyes are sometimes level with the tabletop! Anyway…try these on your next chair–you’ll be surprised.

• Since my theme seems to be soldering-related, and I’ve just mentioned static electricity, here’s one that tries to help one by eliminating the other. It’s an 18 by 30 inch anti-static mat that is made specifically to withstand direct assaults by soldering irons and hot solder. It sells for $57.50. I have several of these, and they work quite well. They also give you a consistently-colored, flat surface to look for small SMD parts you might have just dropped. At my work, even though it’s in Northern California, we make extensive use of anti-static mats, wrist straps, and even anti-static floors, and chairs with little metal chains that droop down to make constant contact with the floor. Even if you don’t feel a jolt, static electricity can and does pass between you and anything you touch. I seem to recall that we have a threshold of feeling that’s somewhere around 5 thousand volts. Anything less may go unnoticed by people, and at the same time, blow out the junction on a MOSFET. We also practice the “touch me before you hand me the pc board” protocol to dissipate these lower-level jolts (much harder to do now with social distancing). Anyway, these are good mats. Remember to ground them to the screw on your AC wall plate or a similar electrical ground spot.

OK, so that’s it for now. I’ll try and add more soon. The young lady in the Prime van said to tell you hi, and that she misses her family.

Dave – K7DAA