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In this question I was told that I should use silver solder to connect the heating element to the power supply.

(I was also told that a ceramic extruder head was the way to go, but I'm working with what I have)

I bought two types of silver solider from Radio Shack:

  • 96/4 Silver-Bearing Solder, Lead-Free 0.62" diameter.
  • 62/36/2 Silver-Bearing Solder, 0.15" diameter.

Is there any reason I should use one of these over the other to power the heading element of the J-Head extruder?

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3 Answers 3

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The first is not suitable. ASTM96TS Sn96Ag4 has a melting point of 221–229 °C according to Wikipedia. Pb96Ag4 would be OK, but that is not lead free so doesn't seem to match your description. Update from comment to explain the letters and numbers: the data comes from wikipedia, the numbers are Tin(Sn) 62%, Pb(Lead) 36%, Ag(Silver) 2%, for example, see below for an electronics solder compound.

Sn62Pb36Ag2 is an ordinary expensive electronics solder (but not lead free), with an even lower melting point.

You need to find a high temperature silver solder, with a melting point of about 305 °C (which confusingly might be a soft silver solder), for example one of these. Hard silver solders melt at 600 °C, that would be excessive in this application.

The nomenclature 'silver solder' came about before lead-free electronics solder was introduced, since when more alloys containing silver have become popular as general purpose solders.

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Use ferrules to join wires, and on your board either solder directly (it doesn't matter what solder you use because it's not going to get hot if your wires are gauged properly). Or use soft copper wires and clamping terminals without the wires being tinned or risk a fire hazard.

Tinning makes the surface harder which makes for less contact area. If it deforms from heat , it can come loose and cause arcs, which is where the fire hazard comes from.

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    $\begingroup$ or risk a fire hazard - could you edit your answer and clarify that point? If the wires are tinned, is that a fire hazard? What exactly is the fire hazard in this situation? It isn't really all that clear, and considering that it is an important safety aspect, it would be worth being expanded upon... $\endgroup$
    – Greenonline ♦
    Commented Jun 28, 2017 at 21:37
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    $\begingroup$ My (uneducated) reading is that this tinning increases the risk of a high resistance joint, compared to clamped soft-copper. but I agree, clarification is important. $\endgroup$
    – Sean Houlihane
    Commented Jun 29, 2017 at 16:52
  • $\begingroup$ Tinning makes the surface harder which makes for less contact area. If it deforms from heat , it can come loose and cause arcs, which is where the fire hazard comes from. $\endgroup$
    – Justin
    Commented Aug 16, 2017 at 20:12
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    $\begingroup$ The terminal blocks are rated for wires terminated in a particular fashion. If you find one that's rated for tinned stranded wires, go right ahead, but those are few and far between and are usually spring loaded terminals, not screw terminals. For screw terminal blocks (female), there are usually only two approved termination types: directly to solid copper wire, or to a stranded or solid wire in a ferrule. $\endgroup$
    – Kuba hasn't forgotten Monica
    Commented Aug 18, 2017 at 17:49
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I can't comment yet, but for those wondering, the issue with tinning the wires is when you are clamping them. Tinning them actually increases the resistance between the wires and terminal, due to making them harder and not getting squished out to make more contact with the terminal. This increased resistance means increased heat, and enough heat means fire.

The reason for the prohibition is that when you fully tin a multistrand wire fully, the solder wicks between the strands of copper and forms a solid block, part of whose volume is metallic solder. When you clamp the solder and copper bundle you tighten the screw or clamp against the solder block, and in time the solder metal "creeps" under the compressive forces and the join loses tension. The wire can then either pull out or cause a high resistance connection with heating.

Source

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