SOLDERING FUNDAMENTALS
#1. A good solder joint will be smooth and shiny and will have a long live span and will not introduce any problems to the
device/circuit. It will not be a blob of solder, but will have smooth flow characteristics that represent uniform heating of all attached leads/wires/components.
#2. A bad solder joint will not look smooth and will not be shiny. It will appear irregular in shape, possibly with holes, craters and perforations, with indentations likely where leads/wires/components are attached, giving a look that they were pushed into to the connection due to poor heating of one or more components. A bad solder joint (cold joint) will likely introduce resistance into the connection where there should be none, and cause problems as far as making a good physical connection in that the component leads will be prone to detaching from the connection.
#3. There are no exceptions to #1 and #2 above NONE.
#4. It is easier to make a good solder joint when you have a good physical connection prior to soldering. When soldering: Use tabs and mounting holes when possible; Twist wires and component leads together when possible; Bend or crimp wire and component leads together when possible.
#5. Clean all wires, component leads, fixtures, connectors, etc., prior to soldering, when possible. This can be accomplished by wiping with alcohol, scrapping with a knife, exacto knife, precision file, emery board, etc. Component leads can be easily cleaned by inserting the end of the lead into needle nose pliers, applying gentle pressure to the pliers, and gently twisting and pulling the lead
through the pliers as if removing a screw. They will emerge bright, shiny and eager to accept solder.
#6. Pre-tin all wires, component leads, fixtures, connectors, etc., prior to soldering, when possible.
#7. Keep the tip of your soldering iron in good condition, i.e., keep it tinned, and keep it clean. Keep a damp/wet (saturated, but not dripping) sponge or a paper towel folded multiple times to make a small square next to your soldering iron to clean your tip and keep it clean as you are soldering. If needed, you can file the tip of your iron into a point (or any other shape), then re-tin it properly before you start soldering.
#8. You can use extra flux to help the solder process, but DO THIS SPARINGLY. Most all solder for electronics will have flux in the solder so in almost all cases adding additional flux is not necessary, and really shouldnt be done. If you do use flux be sure it is only applied to the exact point that it is needed. Excess flux can flow into areas where it is not wanted, which by itself can cause problems, but will also make it easy for solder to flow into unwanted areas and really cause problems.
#9. A bad (cold) solder joint can be frequently repaired by applying the tip of the iron to the bad joint, re-heating the solder and component leads for the solder to flow sufficiently to each lead uniformly. Applying a small amount of flux to the joint can sometimes help. There will be times that in order to repair a bad joint it is easier, and better, to remove all of the old solder and start over.
#10. When you are soldering, always try to position the tip of your iron so that you make equal, uniform physical contact with each item/lead/wire/etc. that you are soldering. Upon making contact with the tip of the iron and the desired components, feed the solder to point of contact between the iron tip and the components, and if done properly the solder will flow evenly to all heated areas. Remove the iron and the solder from the connection simultaneously. Let the connection sit as still as possible for the joint to set properly, on small items this will be almost instantaneous, for large items this will take longer depending on the amount of heat absorbed. The process for pressing the tip to the connection, feeding the solder, removing the iron and the solder, should take only a second or two for most connections soldering to a PC board, soldering component leads, small wires and things of this nature. Again, larger items, such as power connectors, large spade lugs, battery terminals, larger wire etc., will take longer, sometimes much longer, as the extra metal involved will sink more heat.
#11. Dont be afraid to use a soldering iron of sufficient wattage. Yes, heat can damage electronic components and other/attached items. But to solder effectively you have to be sure to heat everything uniformly, it is easier to do this with a 30W iron than it is with a 20W iron. Dont apply more heat than is necessary, but EVEN, UNIFORM TRANSFER OF THE HEAT TO ALL COMPONENTS IS REQUIRED.
#12. Use good quality solder with resin flux in the core. Never, ever, use pipe solder, this may well have an acid flux at the core. Dont use large diameter solder. There are many different gauges of solder available, honestly this is not critical for this hobby, but generally small diameter solder will work better than larger.
My credentials in making this list of fundamentals are fifteen years of experience as an ET working on, repairing, maintaining, calibrating and/or manufacturing diverse types of electronic equipment. Everything from high and low quality test instruments, to in the ear hearing aids, and high performance (extremely high output) ignition systems for US Customs boats, as well as racing vehicles cars, boats, hydroplanes, airplanes, and motorcycles. In my career as an ET, I was known for the high level of my craftmanship, including and especially soldering.
