Monday, 7 September 2015

Soldering - An Important “Tip” from VA3VFO

"Reprinted" from a past issue of Splatter.

By Greg VA3VFO

Good to hear about the Project Nights and interest in soldering skills.

My tips for those starting out are often over-looked or underestimated by even experienced folk, but should especially help our new project builders.

One of the first lessons taught is the requirement of “tinning” the new tip of your iron or gun, (much like “seasoning” a new cast-iron fry pan).It is equally important to continue to make sure the tip remains tinned as it ages and wears down. When neglected, it leads to much frustration, and the beginner may not realize this is the cause of so much grief.

If the joint is not quickly “wicking-up” the wet solder, or if you find you have to really heat up the joint ONLY, chances are you have an oxidized tip that is not holding its “tinning”.

It is very important to apply the solder to not only the joint of the connection, but at the intersection of the joint AND where the tip makes contact with the joint. A dark or blackened tip that seems to repel the solder should be repaired or replaced. For the tip to transfer heat properly, it MUST be “silver/light grey” in colour and accept solder over its total tip contact area. Simply wiping the tip on a cloth or damp sponge won’t work! You have to remove the build up of oxidization and this can be tricky on some types of tips.

Tips usually come with factory plating on the tip. I am not sure of the various plating materials used, but would guess silver or similar alloy. Some tips you have may be copper only. You may tempt to sand, grind or file down the tip to renew its surface. This can destroy or remove the coating of its plating material, which is so important to its ability to hold the “tinning” and to transfer heat. Yes, you may find it necessary to grid down a tip- go for it. Make a specialized tip to solder that micro-small surface mount part, or to squeeze into a tight space, but beware! If you do this, accept that the tip will lose its proper plating finish and will be subject to FAST re-oxidation. So keeping it fresh becomes an ongoing concern.

You will have to watch for poor heat transfer caused by “cold spots” on the tip. These are areas, which stubbornly repel solder- usually from solder flux residue or spots of oxidization. The longer a tinned copper tip sits plugged in, the more it will oxidize! After a good tinning, unplug, let cool and store away. Don’t store a plated or copper tip without a good fresh coat of solder. You may ruin a good tip trying to restore it to take full tinning. When possible, always buy the properly plated tip for your work! Only file or grind a “custom” or old tip if you have to.

Since an oxidized tip will not transfer heat well, it will take longer to heat the material. You likely know that too much heat can render some electronic parts (transistors etc) useless. But often, not enough heat is just as bad. I would much rather apply a high heat to a part for a quick, shorter period of time, than having the part and its support connections, like plastic insulators or the centre core of coax, melt away or become deformed. So “turn UP” the heat by simply keeping a well tinned tip at all times. If you are still having problems with nice wet joints, you may want to use a higher-powered iron (or gun for the heavy stuff, like coax connectors).

One last trick for stubborn tips that just won’t tin properly is to dip them into acid solder flux (used for plumbing, NEVER for electronics). Re-tin them IMMEDIATELY. You can try this if a very light sanding or steel wool pad fails to clean a plated tip. Plated tips can be gently “refinished” but careful not to “peel-way” the factory applied plating. An old tip can be sacrificed or filed into a fine point, but extra special attention to maintaining a “good tin” is paramount once the copper under the platting is exposed. It is just as likely to have a new plated tip “go cold” and not accept solder, so watch for that problem at all times!

Keep the oxidization off your tip. Keep it shiny and hot and you will have mastered the biggest secret of becoming a master solderer…er!

Greg
VA3VFO

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