recommend cheap and corrosion resistant electrical contact material

On 17/04/2021 23:49, mike daniels wrote:
> I'm looking for a low cost contact material that can withstand being exposed to unconditioned warehouse conditions for months without the surfaces becoming corroded or oxides.
> 
> The shape of these will be similar to D cell batteries with a spring on one side and a flat contact on the other.   The device is not a battery but mounts similarly and must work reliable on first install.  No jiggling allowed.
> 
> The flat contact will mechanically retain a stainless steel spring (304) so this contact metal cannot react with stainless.   The spring must be stainless to get the mechanical force we need.  No copper or brass here.
> 
> My knee jerk reaction is to keep everything the same stainless material.  The downside is the battery clip style ones need some bends and shaping that get a little expensive.
> 
> The other downside is we the minimum current passing through this contact is 1mA.   Not very high to "burn" through oxided layer.  We do have 15-30V so that is something but I rather not have to depend on punching through an oxide layer to get contact.
> 
> Thoughts are.
> 
> 
> 1) tinned copper or brass
> 2) Gold plating "LOL  too expensive but maybe not in high enough batch sizes"
> 3) nickle plated brass, copper, tin?
> 4) straight tin
> 5) straight nickle
> 
> 
> Any other contact material/plating options stick out as a winner in this application?
> 

Mould some silver conductive epoxy onto your SS spring.

-- 
Cheers
Clive

On Saturday, April 17, 2021 at 5:50:01 PM UTC-5, mike daniels wrote:
> I'm looking for a low cost contact material that can withstand being exposed to unconditioned warehouse conditions for months without the surfaces becoming corroded or oxides. 
> 
> The shape of these will be similar to D cell batteries with a spring on one side and a flat contact on the other. The device is not a battery but mounts similarly and must work reliable on first install. No jiggling allowed. 
> 
> The flat contact will mechanically retain a stainless steel spring (304) so this contact metal cannot react with stainless. The spring must be stainless to get the mechanical force we need. No copper or brass here. 
> 
> My knee jerk reaction is to keep everything the same stainless material. The downside is the battery clip style ones need some bends and shaping that get a little expensive. 
> 
> The other downside is we the minimum current passing through this contact is 1mA. Not very high to "burn" through oxided layer. We do have 15-30V so that is something but I rather not have to depend on punching through an oxide layer to get contact. 
> 
> Thoughts are. 
> 
> 
> 1) tinned copper or brass 
> 2) Gold plating "LOL too expensive but maybe not in high enough batch sizes" 
> 3) nickle plated brass, copper, tin? 
> 4) straight tin 
> 5) straight nickle 
> 
> 
> Any other contact material/plating options stick out as a winner in this application?


Its actually 302 stainless not 304.  not sure how much of a differnce that makes.

Thanks for the recommendations.   

Another constraint I neglected to mention is that the surface should be solderable with typical leadfree (SAC305) type solders and fluxes.    No heavy duty fluxes as it could be soldered directly to a PCBA with solder paste.

mike daniels <dmcousin2000@gmail.com> wrote:
> I'm looking for a low cost contact material that can withstand being exposed to unconditioned warehouse conditions for months without the surfaces becoming corroded or oxides.  
> 
> The shape of these will be similar to D cell batteries with a spring on one side and a flat contact on the other.   The device is not a battery but mounts similarly and must work reliable on first install.  No jiggling allowed.
> 
> The flat contact will mechanically retain a stainless steel spring (304) so this contact metal cannot react with stainless.   The spring must be stainless to get the mechanical force we need.  No copper or brass here. 
> 
> My knee jerk reaction is to keep everything the same stainless material.  The downside is the battery clip style ones need some bends and shaping that get a little expensive.
> 
> The other downside is we the minimum current passing through this contact is 1mA.   Not very high to "burn" through oxided layer.  We do have 15-30V so that is something but I rather not have to depend on punching through an oxide layer to get contact.
> 
> Thoughts are.
> 
> 
> 1) tinned copper or brass
> 2) Gold plating "LOL  too expensive but maybe not in high enough batch sizes" 
> 3) nickle plated brass, copper, tin?
> 4) straight tin
> 5) straight nickle  
> 
> 
> Any other contact material/plating options stick out as a winner in this application?

spring copper might work. Strong, can be soldered, doesn't corrode too 
bad, no small batch plating needed, good track record for electrical use 
etc.