Soldering is a method for chemically joining items using heat. There are many types of soldering, but by far the most common is using a tin alloy to join copper parts. This is a staple of electronics manufacturing, and the focus of this article. The "Basics" section will give you some very condensed core insights to get started with soldering without missing important information.

See also: Soldering Equipment

Basics

• Do not use the soldering iron to exert physical force. Use pliers or other appropriate tools if you have to hold something in place or apply pressure.
• There is a substance called flux that is a component of solder. Basically this serves to make the liquid solder flow correctly and distribute itself onto the component pins/pads. Flux is completely essential to soldering, and incorrect usage of flux is the most common source of error and misery for novice solderers. 
  • Flux is single use, meaning that it will only function for a single heating. When initially soldering a joint, the flux in the solder thread will be sufficient. If you have to reheat a joint, additional flux must be added externally. At Omega Verksted, you can find additional flux in the Poison Fridge.
  • When adding external flux, don't be afraid to add too much (although please don't waste excessively)
• There should be a small amount of tin on the soldering iron when it is in use, for any soldering operation. This will increase the contact surface area and improve thermal transmission.
• If there is oxide on the soldering iron (brownish-black stains)
• In general, soldering a joint should take around 2-5 seconds.
• In general, the solder joint should have a "nice" slope. It should not be too concave or convex.
• If the solder joint is not heating up fast enough, almost universally the thing to do is to use a bigger soldering tip. A very coarse rule of thumb is that the soldering tip should be around the same size as the pad on your PCB. You can ask a board member if you can't find a bigger tip.
  • The Metcal soldering stations at Omega Verksted do not allow for adjusting the tip temperature, because they automatically use the optimal tip temperature for the lead free solder stocked by Omega Verksted.
• Use a claw stand ("helping hand") to align the items you are soldering if necessary. Alternatively you can ask someone to help you hold something.
• When finished, add some tin to the soldering iron. This will extend the lifetime of the equipment. 

Desoldering

• When using a solder wick, you should add some flux to the solder joint you want to desolder.

Advanced

The goal of optimal soldering is to create an intermetallic layer (the layer of bronze between the copper and the tin) of the optimal thickness. This has been empirically determined to be around 1μm. For most applications, this will be achieved when the solder is heated to the correct temperature, the solder flows across the copper to cover all the areas of the joint ("wetting"), and the joint is heated for around 2-5 seconds. 

Reflow Soldering

The most common technique in industrial electronics manufacturing. Generally gives better results for small or fine-pitch components unless you are extremely good at hand soldering. Omega Verksted has facilities for doing reflow soldering.

See Loddeovn.