Soldering star on aluminum

Flashlight Modding and DIY Parts
1

Hi,

I did solder testwise a star to a brass pill, with no problems
soldering the wires back to the star was a lot harder with medium tip had to increase temperature to get it done

So I tried to solder to aluminum with different solder composites and 3 types of flux for electronics
But I had no luck with that even with the internet tip to sand the metal below a oil film then solder

So I ordered now
2 types of aluminum solder wire with flux
230°C contact solder with flux
description says heat up the aluminum and rub the solder to it
lets see if its possible to solder without changing color of the anodisation using soldering iron

380°C but can be used with normal solder iron
flows on aluminum
if color change of anodisation is no problem heat up the head and stick the solder to it

flux that make normal solder
lets solder flow on aluminum capillary
says I can use normal electronic solder with iron for aluminum

2

Changing anodisation color is not biggest problem. Dielectic layer will be unglued and will start “crack”.
The best way to solder alu alloys is using special rods like hts-2000, but they require 600+ deg.C temperature.

3

H III anodisation cracks I noticed that on my Klaruas lights
It did crack between 80 and 120°C

the usual Cheaper lights like Convoy and Eagle eye had no cracking

4

So I did manage to solder my Eagle eye X6 and the dead Klarus XT11GT

With the 230°C I could solder bare aluminum fine,
but the aluminum from flashlight seems to be a compond not liking the low temperature solder at all
or I did not heat enough
My IR thermometer goes only to 280°C

Its not easy and you will need the* 380°C* solder so the anodisation will change color
Basically heat up the head with a gas burner and then rub the solder on the aluminum till it sticks
no flux needed if the aluminum is clean

The MCPCB didnt like 400°C but flux worked well to eat the anodisation
the 380°C solder does not look shiney like the low temperature one

the flux even eats anodisation away
funny thing is the solder flows between anodisation and aluminum, so if you scatch the anodisation off you get a reallynice tinned aluminum
on the left the 230°C solder with flux the solder did not stick to surface, but the aluminum got sealed by flux
in the biddle dremeld the anodisation away used flux and rubbed 380°C solder
the right is sanded the anodisation odd and rubbed the 380°C solder to the hot aluminum

the darker anodisation on the left is where the flux eat away the anodisation and solder flowed between anodisation and aluminum
left cleand and added 380°C solder
the solder soes not shine like the low temperature one

Wit low temperature solder I could solder as star and aluminum foil without a problem

5

Anodization is thermally insulating, so maybe that’s part of the problem?

6

the funny part is once the solder is sticking to a spot the solder slowly eats between the anodisation and aluminium
in about 10 minutes it eat all the way
just took a knive and scratched the anodisation away a perfectly tinned aluminum piece