[TowerTalk] Crimp on Coax connectors

[jimlux]

The important thing about crimp connectors is that they don't suffer 
from the brittleness of the solder, particularly under temperature 
cycling or vibration.

Solder work hardens. Copper work hardens. etc.

A properly made crimp connection is a gas tight connection between the 
conductor and the connector that (if the connector was properly 
designed) has just the right amount of elastic deformation, so that 
under temperature swings and vibration that the gas-tightness persists.

Solder is weak (6000-7000 psi)and has a CTE of about 25 ppm/C  (thats 
for eutectic Pb/Sn... the low lead or lead free solders are all over the 
place)

Copper CTE is about 16-17 ppm/C
Brass is about 18-19  (what 083-1SP plugs are made of)
SS is 14-19 (depending on alloy)
Aluminum is 21-24

So soldering a connector is putting a mechanically weak material with a 
high CTE between two things with low CTE, which is asking for trouble.

Likewise with vibration - depending on the relative "stretchyness" of 
the materials and their strengths, you're putting the mechanical loads 
on the weakest materials (think two lengths of piano wire with a cotton 
string in series)

Then there's the whole "creep" phenomenon (gradual inelastic deformation 
over time under strain) - NIST says secondary creep is the dominant 
deformation mode at temps above half the melting point (absolute temp).
Eutectic solder melts at 456K (183C), so 1/2 Tm is 228K (-45C). As they 
say: "That is, standard SnPb solder readily creeps at, and well below, 
room temperature"

https://www.metallurgy.nist.gov/solder/clech/Sn-Pb_Creep.htm

These kinds of things really come up when soldering big parts with lots 
of pins on boards, but they're equally applicable to connectors.

Basically, "solder isn't structural" and you shouldn't be using it for such.

(this doesn't include hard solder/silver solder, which is more like brazing)


You don't see many soldered connectors in automotive applications, for 
instance.