RMA-223 or NC-559: which flux for phone repair

These are the two fluxes you will find on almost every repair bench, and the choice comes down to the job rather than the price.

The short answer

Doing BGA work and reballing — take RMA-223. Everyday work with small components — NC-559.

RMA-223: when you need tack

The defining property of RMA-223 is how tacky it is. Apply it to a pad, place a solder ball or a chip, and it stays put while the hot air runs. For reballing that is essential.

The price of that tack is residue. Wash the board with isopropanol afterwards.

NC-559: when you would rather not wash anything

NC-559 is no-clean. It smokes less, does not darken contacts and needs no washing. Solder small parts all day and you feel the difference by lunchtime.

If you can only buy one

Take RMA-223. It handles small work too, you will just have to clean up after.