A soldering gun appears just as the name implies: like a gun. These devices are generally of a much higher wattage than a soldering iron. Soldering guns have a "trigger" switch that causes the tip to heat when it is pressed and held. When it is put down, the trigger switch opens and the gun is then off. Though soldering guns heat rapidly, they are generally too hot for use on PCBs, light- gauge wire, and small semiconductor devices. They usually have a much broader tip making use difficult on solid-state PCBs. Guns work well on heavy gauge wire, such as 4 gauge or larger, because the large wire allows heat to sink away quickly from the area being soldered. The high output of the soldering gun is therefore required. A soldering iron cannot supply enough heat quickly enough to get the solder to flow into a large gauge wire. This will often result in a poor solder connection.
Soldering irons usually do not exceed about 35 watts. They are "on" whenever plugged in, and should be returned to a soldering iron stand when not in actual use. A wide variety of tips are available for most professional irons, ranging from conical, screwdriver, chisel, and in different dimensions and heat ranges. 700° F tip is the most common.
Tips do wear out in time, and will need to be replaced occasionally. Using a namebrand iron such as Weller/Ungar, will ensure that you can find a replacement tip of the desired type when the time comes, and even a new heating element if needed.
Using an anti-seize compound on the new tip can make replacement much easier when the time comes. Due to corrosion, an old tip can be difficult to remove from the iron.
Cleaning the soldering iron tip is required occasionally to remove a buildup of burned flux. The buildup can act as an insulator making soldering difficult. Many soldering stands come with a small sponge which can be wet to wipe the tip. The problem is that the water rapidly cools the tip and the buildup then will not come off easily. A light sandpaper will remove buildup and clean the tip quickly, but can shorten the life of the tip if used vigorously. Tips are not expensive, so the tradeoff is not a big one.
Soldering stations generally provide a variable temperature adjustment for the iron, and some of the more sophisticated units will have a vacuum device for collecting melted solder. Some type of desoldering is generally required when removing and replacing soldered parts, especially from printed circuit boards.
Other types of irons include battery-powered units and gas/butane. These are preferable where commercial power is not available or inconvenient to access.
Removing parts from a PCB generally requires that the solder be removed so the part can be freed from the board. As soon as the heat source is removed, the solder will solidify quickly, usually before the part can be grasped and pulled free. Two devices for removing melted solder from a connection are the desoldering pump and solder wick.
Desoldering pumps (solder sucker) can be either a small rubber bulb with a hard plastic tip, or a spring-loaded cylinder type. The spring-loaded type is the most popular. The pump is "cocked", and when released, it creates a short but powerful vacuum at the tip. This vacuum action will pull melted solder off of the metal parts so they can then be easily removed. Desoldering pumps and bulbs clog easily as the solder often solidifies in the tip which restricts the vacuum action. They therefore require constant cleaning.
Solder wick works more slowly, but just as well as a pump. Solder wick is a fine copper braid, available in various widths. Wick is placed in contact with the solder joint and heated directly with the iron. When the wick and solder reach the melting temperature, the solder will flow into the braid of the wick by capillary action. For small connections such as IC pins, a narrow wick is best. Used on larger connectors, several inches of the wick may have to be used to "wick" all of the solder from the connection. A wider wick would be called for here. The "wicking" action works very well in removing solder, and can leave connections devoid of solder with a little practice. A difficult connection can sometimes have new solder added to it to aid in the start of wicking action. Solder wick has a shelf life as it does not work well if a layer of corrosion forms on it. Most quality solder wick products have an anti-corrosion coating to prevent this.