Step 1: Recommended Tools and Supplies
For solder, we recommend starting out with a lead-based solder, usually called 63/37 (63% tin, 37% lead by weight) or 60/40 rosin cored solder. Get whatever's cheaper; there's unnoticeable difference in hand soldering between 63/37 and 60/40. The rosin is a flux that cleans parts so solder will bond with them. Avoid solid wire (no flux core) and acid cored solder (for plumbing, too aggressive for circuits). We recommend solder that's about .031" in diameter for most through-hole components. Water-soluble flux is much more aggressive than rosin, and these residues must be cleaned. Lead-free solder melts at a higher temperature, and doesn't wet or spread out as readily, so it will be slightly harder to use.
- Needle Nose Pliers: Useful for pre-bending leads, pulling out components during de-soldering, and a lot of other things.
- Wire Strippers: Two types are shown: the yellow ones can be adjusted to strip any size wire (good for small 28-30 AWG ribbon cable wires) whereas the red handled ones have several fixed hole sizes.
- Flush Cutters: Used to trim leads close to the board after soldering .
- Clamps: Oftentimes just resting your board on a table will be fine, but the clamps are especially helpful when desoldering parts or soldering wires together.
- Solder Sucker and Solder Wick: Both are inexpensive ways to remove solder. The sucker is a spring loaded tube that vacuums out solder and the wick is a fine braid of flux coated copper that soaks up solder.
- Multimeter: Some multimeters have a continuity check that beeps if there is a complete circuit. This is very useful for making sure parts are connected or disconnected when there're a lot of wires and parts.
-Pink Erasor: (not shown) A pink eraser can be used to rub off oxides from older components and boards without risking damage to the parts.
Step 2: What Order and Which Way to Insert Components
- If there are tall components right next to shorter ones, you avoid having to bend already-installed taller components out of the way while inserting shorter ones later on.
- One of the best ways to hold a component in place is to insert it, and then lay the board upside down so the table surface keeps the component in place. If you install shortest to tallest, the tallest component will always be the one you're currently working on.
It's also helpful to install components so that the value can be read in the same direction as the surrounding text. For instance, install all the resistors with their tolerance bands on the right so that all the values can be read without having to rotate the board.
Make sure the notch on ICs matches the notch on the board.
Step 3: Prebend Leads for Easy Insertion
Just fyi, for sensitive circuits (ie, military, space), serrated pliers aren't allowed because they might create a divot in the lead that could weaken and fail from vibration.
The "right" way aside, just bending the leads with fingers can work well, too
Step 4: Clinch Leads to Hold Parts in Place While Soldering
The only downside is that parts can be harder to remove later. Other methods to hold things in place while you flip the board over include just having the table surface hold it in place, and also using tape. For instance, header pins can't be bent, so the table is used to hold them up in the last picture. You can also place some solder on one empty pad, and then reheat that pad while pressing the part through to get started.
In industrial manufacturing processes, parts are either held in place by a small drop of adhesive (for surface mount) or by clinching the leads. Boards are then transported via conveyor over molten fountains of solder (google wave soldering).
Step 5: Make sure LEDs and Some Capacitors are Inserted in the Right Direction
it's OK if the yellow plastic on ceramic capacitors (disc shaped) goes beneath the top level of the board and touches the solder, it just can't show through to the other side (according to IPC, the industry's soldering standards organization).
Step 6: Soldering
Usually people say that joints should come out looking shiny, but this is only true for lead-based solder. Lead-free joints will have a duller surface finish, but still be perfectly fine joints. With either type, the solder should cling to or wet the surfaces, and not just sit on top of them. It should form a smooth ramp and feather out across the pad. The above link also has some galleries of good and bad joints.
It's a good idea to check the part for correct alignment after soldering one pin. Adjustments can easily be made at this point by reheating that one pin, but once multiple pins have been soldering, the part may need to be completely removed to adjust it.