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Soldering a PCB onto an Aluminum pin.

V

vahid

Jan 1, 1970
0
We have an application where we are soldering a PCB onto aluminium pins
which have been embedded in plastic. The pins are about 10mm long and 3
mm diameter with a shoulder that takes the diameter down to 0.9mm where
the pcb would be soldered.

Questions:
1) Do i have to treat the Al before soldering - some say that i should
electroplate it with silver, which sounds expensive for a consumer
product.

2) Is there lead-free solder for this?

3) Can we use normal solder mask on the board? or do we need also need
some special solder on the solder mask on the PCB?

4) Will the heat not just dissipate into the pin and melt the plastic
before we can get the solder wetting the aluminium?

Thanks,
Vahid.
 
C

Chris Carlen

Jan 1, 1970
0
vahid said:
We have an application where we are soldering a PCB onto aluminium pins
which have been embedded in plastic. The pins are about 10mm long and 3
mm diameter with a shoulder that takes the diameter down to 0.9mm where
the pcb would be soldered.

Why do it this way? I mean, couldn't you simply use a spacer and a
screw which can go into the plastic? Or can you get the pins threaded
on the reduced shank so a nut can fasten the PCB? Otherwise, soldering
to the aluminum will present many problems...

Questions:
1) Do i have to treat the Al before soldering - some say that i should
electroplate it with silver, which sounds expensive for a consumer
product.

I haven't heard of doing this, as I have soldered aluminum directly. If
you could afford the cost of added treatments to the pins, why not just
design them to be a normal threaded standoff, or spacer?
2) Is there lead-free solder for this?

Yes. What works to solder Al at low temps is Sn91Zn9 alloy. I got mine
from indium.com which is alloy #201. It requires a flux (Indium's flux
#3) which is rather nasty, containing organic fluorides and other glop.
This is the bad part. You don't dare breath the fumes like you can
get away with when using rosins. You must also clean away the flux
residues very thoroughly. The good news is that it is actually not
terribly difficult to make very good flowing solder joints with this
solder/flux combo. The alloy melts at 199C which is slightly under
typical SAC305 lead-free.

Repeat, if you can deal with the cost of the exotic soldering operation,
why not just use ordinary mechanical methods?
3) Can we use normal solder mask on the board? or do we need also need
some special solder on the solder mask on the PCB?

Don't know if there is any issue with PB mixing with the Sn91Zn9. I
soldered aluminum wire to pads on a PCB, which I think were just plain tin.
4) Will the heat not just dissipate into the pin and melt the plastic
before we can get the solder wetting the aluminium?

Yes, which is another reason why ordinary mechanical means are probably
wiser.


--
Good day!

________________________________________
Christopher R. Carlen
Principal Laser&Electronics Technologist
Sandia National Laboratories CA USA
[email protected]
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.
 
C

colin

Jan 1, 1970
0
vahid said:
We have an application where we are soldering a PCB onto aluminium pins
which have been embedded in plastic. The pins are about 10mm long and 3
mm diameter with a shoulder that takes the diameter down to 0.9mm where
the pcb would be soldered.

Questions:
4) Will the heat not just dissipate into the pin and melt the plastic
before we can get the solder wetting the aluminium?
probably

how about a spring clip, pushes over the pin and wont come off, looks a bit
like a bent washer with pointy bits on the inside wich slide easily one way
but dig in when going the other way

Colin =^.^=
 
C

Clifford Heath

Jan 1, 1970
0
colin said:
how about a spring clip, pushes over the pin and wont come off,

They don't work for making reliable electrical contact to aluminium
if they're subject to even the slightest vibration. They gradually
into the Al until they're not tight, then you get oxide and no
contact.
 
C

Clifford Heath

Jan 1, 1970
0
Clifford said:
They gradually
eat

into the Al until they're not tight, then you get oxide and no
contact.

sorry for the unintended deletion.
 
C

colin

Jan 1, 1970
0
Clifford Heath said:
sorry for the unintended deletion.

the aluminium is going into plastic, so I cant see why there is a need for
electrical contact, if there is the OP didnt mention it.

mechanicaly, aluminium probably isnt the most suitable material for this.

Colin =^.^=
 
I

ian field

Jan 1, 1970
0
vahid said:
We have an application where we are soldering a PCB onto aluminium pins
which have been embedded in plastic. The pins are about 10mm long and 3
mm diameter with a shoulder that takes the diameter down to 0.9mm where
the pcb would be soldered.

Questions:
1) Do i have to treat the Al before soldering - some say that i should
electroplate it with silver, which sounds expensive for a consumer
product.

2) Is there lead-free solder for this?

3) Can we use normal solder mask on the board? or do we need also need
some special solder on the solder mask on the PCB?

4) Will the heat not just dissipate into the pin and melt the plastic
before we can get the solder wetting the aluminium?

Thanks,
Vahid.

AFAIK you can tin the pin with alusol and then ordinary solder will take.
 
J

James Beck

Jan 1, 1970
0
AFAIK you can tin the pin with alusol and then ordinary solder will take.

Gotta' watch which alusol you mean.
Around here alusol is a machining lubricant for aluminum.
If you want the flux look for "Finex Alusol" or search for aluminum
soldering flux.

Jim
 
I

ian field

Jan 1, 1970
0
James Beck said:
Gotta' watch which alusol you mean.
Around here alusol is a machining lubricant for aluminum.
If you want the flux look for "Finex Alusol" or search for aluminum
soldering flux.

Jim

I didn't know there was another product with the same name, but if I did I
would have figured that the context made it obvious which one.
 
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