Isn't Kester 44 descriptive of the flux, not the solder? I use it too, and that solder flux is available in solder with or without silver.
I have read that the magic of Kester 44 flux is the 0.44% of bromides and chlorides it has (https://www.kester.com/downloads/data-sheets). That may not be suitable for all applications.
44 possesses excellent fluxing ability; the flux residues are non-corrosive, non-conductive and do not require removal for most applications under normal conditions of use.
I have use CYNEL solder Sn60Pb40 and Alpha Sn63Pb47, Felder Sn60Pb40 and STANNOL Sn62Pb36Ag2 (from my experience flows better from the others). I have never use Kester. Do you beleive is above all the brands that I 've mentioned?
Also I remember that I 've read here on the forum in another old thread that the Felder is the best lead free solder and I would like to try it but for some reason always I leave for a future.
Any recommendations are welcomed.
https://www.conrad.com/en/p/felder-lottechnik-iso-core-clear-sac305-solder-reel-sn96-5ag3cu0-5-0-250-kg-0-5-mm-2226454.html
It’s the combination of good flux and the alloy (mostly tin, a bit of copper, and trace amounts of nickel and germanium; the last two improve flow quite a bit).
Mouser and Digi-Key both carry Kester 44. Unusually, in this case Mouser has the better parametric search, because they have a field for the flux amount. For Kester, size 66 is the 3.something-percent.
It’s the combination of good flux and the alloy (mostly tin, a bit of copper, and trace amounts of nickel and germanium; the last two improve flow quite a bit).
Mouser and Digi-Key both carry Kester 44. Unusually, in this case Mouser has the better parametric search, because they have a field for the flux amount. For Kester, size 66 is the 3.something-percent.
Wikipedia has a long list of solder alloys : https://en.wikipedia.org/wiki/Solder_alloys
You can see in the description what addition of various percentages of Silver or Copper do to the solder.
Euctetic formulations should be better most of the time ... for example 63/37 is better than 60/40, but 60/40 is more user friendly, more bad soldering iron friendly (stays liquid / soft for longer time, stays liquid within a wider range)
ex
Sn63Pb37 183[19] Pb Yes Sn63, ASTM63A, ASTM63B. Common in electronics; exceptional tinning and wetting properties, also good for stainless steel. One of the most common solders. Low cost and good bonding properties. Used in both SMT and through-hole electronics. Rapidly dissolves gold and silver, not recommended for those.[8] Sn60Pb40 is slightly cheaper and is often used instead for cost reasons, as the melting point difference is insignificant in practice. On slow cooling gives slightly brighter joints than Sn60Pb40.[17]
Sn62Pb37Cu1 183[18] Pb Yes Similar to Sn63Pb37. Copper content increases hardness of the alloy and inhibits dissolution of soldering iron tips and part leads in molten solder.
Sn62Pb36Ag2 179[5] Pb Yes Sn62. Common in electronics. The strongest tin-lead solder. Appearance identical to Sn60Pb40 or Sn63Pb37. Crystals of Ag3Sn may be seen growing from the solder. Extended heat treatment leads to formation of crystals of binary alloys. Silver content decreases solubility of silver, making the alloy suitable for soldering silver-metallized surfaces, e.g. SMD capacitors and other silver-metallized ceramics.[15][17][22] Not recommended for gold.[8] General-purpose.
Sn60Pb40 183 190[5] 188[6] Pb Near Sn60, ASTM60A, ASTM60B. Common in electronics, most popular leaded alloy for dipping. Low cost and good bonding properties. Used in both SMT and through-hole electronics. Rapidly dissolves gold and silver, not recommended for those.[8] Slightly cheaper than Sn63Pb37, often used instead for cost reasons as the melting point difference is insignificant in practice. On slow cooling gives slightly duller joints than Sn63Pb37.
Below are some of the solder wires that I have used.
I have soldered connectors with gold plating and SMD ceramic capacitors with Sn60Pb40, Sn63Pb37 and Sn62Pb36Ag2 but I have never noticed an optical defective or circuit failure. The wikipedia refers that "Rapidly dissolves gold and silver, not recommended for those" Sn60Pb40, Sn63Pb37 Vs Sn62Pb36Ag2. Maybe this is practically noticeable in high frequencies in level of loses?
I have soldered connectors with gold plating and SMD ceramic capacitors with Sn60Pb40, Sn63Pb37 and Sn62Pb36Ag2 but I have never noticed an optical defective or circuit failure. The wikipedia refers that "Rapidly dissolves gold and silver, not recommended for those" Sn60Pb40, Sn63Pb37 Vs Sn62Pb36Ag2. Maybe this is practically noticeable in high frequencies in level of loses?No. As already explained to you multiple times (once by me, once in the wiki article cited), the danger is in dissolving away thin plating on ceramic. Once it’s dissolved away, there is no conductor left. It would also be a problem if soldering iron tips were made of silver or gold, but they are not.
Gold contamination makes leaded solder brittle*, so high-reliability applications (aerospace, military) specify that thick gold plating must be removed (either by rinsing in a solder pot twice, or by tinning with solder, then wicking it away) before making the joint. (And for SMD components, even thin gold plating must be removed.)
*technically, it does the same to lead-free, but the effect is much smaller so it’s normally ignored.