How to solder this?

[Orpheus 7]

Rosin (aka colophony) is basically purified pine resin, heated to drive off the terpenes, etc. It's the stuff that forms the core of the rosin core solders you get at the electronics shop

 

Chemically, it's mostly abietic acid, a mild organic acid that is generally inactive unless heated, and pretty mild even then. They say you should thoroughly clean it from sensitive or delicate PCBs, and I do (now) to be on the safe side, but I've also seen it sit on solder joints for decades without ill effect -- it anything it seems to protect them from oxidation. I have 30-year old projects with big drops of it on the joints, that still work fine, and old modules/test instruments with visible resin residue from before I was born. But yeah, cleaning it thoroughly is "best practice" so that's what I recommend

 

You can get "pure rosin" from Deal Extreme (an amberlike solid, sold as solid clear blocks, probably intended to rosin bows for stringed instruments), crush it in a vise and dissolve it in isopropyl alcohol (rubbing alcohol) as a base for custom solders. I recommend using at least 95% isopropy rather than the more common 70%, because the water gets in the way. Also, add the alcohol sparingly, and let it sit a couple of days before adding more. It takes a long time to dissolve, so if you think you added enough, you probably added too much -- unless you *want* a watery rosin. I don't mess with that any more -- I've got too many other things to do-- but I used to enjoy making different consistency rosins. These days I prefer the yellow pastes on DealExtreme. Just be aware that they have some misleadingly labeled solderpastes which are actually solder powder suspended in rosin -- I find that very useful, too [applied with a toothpick to SMDs, or applied with a stencil to SMD PCBs) but it's a completely different beast from plain rosin, so make sure you know which you are getting.

 

I should warn you that fumes from soldering with rosin may cause colophony asthma with cumulative exposure. It depends on many things, including personal susceptibility (I've been breathing those fumes since I was 10, with no ill effect), but it can be a real hassle, and it's permanent. In the UK it's the #1 occupational allergy, and a real headache for retraining programs. So work in a well-ventilated area, with at least a small fan blowing the fumes away from you.

 

BTW, I get my Tix sticks, flux and antiflux from Mile Hi Clock Supplies I don't think he's changed his prices since the 90s. In fact it's time to place another order ... my tube got brittle and leaked all over my storage tray.