Most soldering iron tips are furnished tinned ready for use. The ones in our labs are already tinned.
With your solder close by and the solder sponge dampened (not saturated), turn on your soldering iron. After about two minutes, quickly swipe the tip thru a groove in the sponge. Then liberally (1-1.5in of solder) apply solder to the tip and back about 3/8 inch. Don't wait until the tip is fully hot and let it set a few minutes, because it will form tarnish on the tip. The tinning inhibits oxidation of the iron-plated tip. The tip will smoke for a few minutes while the flux burns off. Clean the burnt flux off the tip with the sponge again. Then apply a small amount of solder to the iron tip again for a protective coating and thermal bonding. Now you are ready to solder.
Warining: The tip temperature is about 400 degree C and the solder becomes completely liquid at 361 degree Centigrade. Splattered solder will stick to some clothing and will melt thru polyester or nylon clothing (like $400 gortex jackets) and of course will burn you slightly.
Begin with a damp sponge. Heat the soldering tip, wipe it off on the sponge lightly, and apply solder to the tip and back about 3/8 inch. Repeat this light tinning process every time you begin a session of soldering.
Push the component leads thru the holes in the board completely and bend them back slightly to hold the component on the board.
Note: (If you are installing components vertically, leave about 1/8 inch between the bottom of the component and the board. If you don't, a small push on the component will snap it off due to leverage available to the vertical orientation.)
With a very small solder blob on tip for thermal coupling, hold the soldering iron tip against both the wire and circuit board foil at 45 to 60 degree angle (Figure 1).
The tip should be held at 45-60 degrees (near vertical) so that pressure is more down on the foil, rather that trying to push sideways on the foil. That way there is less chance that a combination of overheating and sideways pressure could cause the foil to lift or slide across the pc board.
Let the foil and wire heat for 2-3 seconds. Touch the solder to wire/foil joint (not to the iron tip) (Figure 2). Does solder freely flow into the juction? If not, wait another sencond to two at most.
When the solder begins to flow, let it spread smoothly down and across the foil, and wicking up the component lead. Keep solder tip in contact with wire/foil joint and let the heat soak through. Don't pile on the solder.
Carefully raise the iron tip pulling up and away from the wire/foil joint. Be careful not to wiggle the component or the leads. Let it cool before touching the area.
A second or two after the iron is removed, the joint should appear shiny and smooth, (Figure 3).
If the solder in the joint looks crystalline, or has a grainy texture or is made up of blobs or balls of uneven solder flow, you have a cold solder joint. Cold solder joints are poor conductors and can make your circuit inoperable.
To fix cold joints, simply apply the soldering iron tip again, perhaps in a slightly different position and apply a tiny amount of solder to the tip/joint junction to facilitate heat transfer. Reheat the joint and check for good apparence.
Questions, suggestions? Let me know......Mail to:
traylor@ece.orst.edu