Conductivity
The biggy. This is the factor which attracts the most heated and enthusiastic debate. Everybody wants their mod to hit like a high speed train derailed en route to flavour town. It’s all about a hard hitting 4.2v straight to the cake hole, with no messing about on the way. We get it. We like it. But unfortunately it just really isn’t that simple…
Without getting into the main causes of “voltage drop” (we’ll look at that another day), people are generally aware that the more conductive a contact material is, the better it is at passing that voltage from your battery to your atomiser, and that then must be an important factor in deciding which material to use. With very good reason, we wouldn’t normally choose contacts made of materials like rubber (although coductive rubber does exist). Rather we’d normally use contacts made from metals like silver, copper, or silver plated copper.
Each of these metals are superb conductors of electricity. Electrical conductivity is the measure of how effectively electric current flows through a given material. The more conductive a given material is, the less electricity will be lost as the current travels through it from point to point. This is caused by how “free” a certain type of electron (Valence Electron) is to move in the material under force, giving us what we call electrical “current”. And these metals have awesomely available electrons so pass as current brilliantly, thus making them superb materials of choice for a mod. The higher the conductivity the better.
Resistivity
Alongside the conductivity of a material, another factor we need to consider is the “resistance” of that material itself. As vapers we should all know roughly what resistance means. Electrical resistivity is the measure of how much a material resists passing an electrical current through it. The higher the resistivity the harder it is to pass current and the more electricity can be lost on the way. The lower the resistivity then the easier it will be for current to pass, making it a quality we definitely need in contacts.
With me so far? Good. To put it simply, we want a material that has a HIGH conductivity and LOW resistivity. Below is a table showing these for the most common materials we use in our mods.
|
Material |
Resistivity Ω·m
|
Conductivity % IAC |
|
Silver |
1.591E-08 |
108.40 |
|
Copper (Pure) |
1.710E-08 |
101 |
|
Copper (Pure Annealed) |
1.724E-08 |
100 |
|
Gold |
2.463E-08 |
70 |
|
Aluminium (99.9%) |
2.655E-08 |
64.94 |
|
Berrylium |
4.00E-08 – 4.43E-08 |
38.9 – 43.1 |
|
Stainless Steel |
6.897E-07 |
2.5 |
Source: Copper Wire Tables, (Technical report). Circular of the Bureau of Standards No.31 (3d ed.). United States Department of Commerce. October 1, 1914.
As you can see, top of the table is Silver, with Copper following not far behind. Both excellent conductors, with not much in it, but this is where things start to get very interesting indeed.
The Fascinating Case of Silver Plated Copper
This material consists of a core material, usually a copper alloy, which is either electroplated or electroless plated in a silver alloy. This means you get the conductivity benefits of copper with some of the aesthetic and ease of maintenance gains of using solid silver.
But “what about the Skin Effect?” I hear some Vape Boffins cry! The “skin effect” is where the current passes mainly through the outside surface of a material, with opposition being higher at the core. So if you had a silver plated material you would get the high conductivity of solid silver at a fraction of the cost. But if only that were the case for us! The Skin Effect only occurs when using an Alternating Current (AC), so is great for headphone connectors and items of that nature, but negligible for the Direct Current (DC) applied when directing electricity to our atomisers. With plated contacts they will only be as conductive as the material that is plated, and in some instances the quality of the copper being plated and the purity of the silver used can be variable to say the least.
Further to this, the silver plating may be done via an electroless process, whereby the core material is first coated in nickel which allows the sliver to bond and plate onto the copper core. With wear and tear (particularly from arcing) and depending on the micron thickness of the plating, it may not be too long before you have contacts showing the nickel or copper beneath. This negates any of the maintenance benefits plating may have provided.
Silver vs. Copper vs Silver Plated
Again, this is where several more factors guiding our choice need to be considered.
Cost
Solid silver is a far rarer metal than is copper, and this scarcity is reflected in its price. It is considerably much more expensive than copper or silver plated metals. For some this is an important factor. For others the benefits to using solid silver far outweigh any cost differentials.
Maintenance
It’s well known that looking after and cleaning your contacts is key to a well performing device. All the materials we use for contacts will oxidise, thus tarnishing and making them look a little worse than their best. Silver tarnishes more quickly than copper, but again here is a surprising advantage. The material formed by oxidisation (Silver Oxide) is actually a conductive material itself. So whilst the contacts may appear dirtier more quickly than copper, the overall performance will not be noticed as soon. This is because the oxidation formed on copper is non-conductive. The more tarnished they become the less conductive the contacts are and the sooner you will notice a decline in performance. Plated contacts will provide the same maintenance benefits as solid silver, but extra care must be given when cleaning to avoid damaging the plating and exposing any material beneath.
Aesthetics
A rather simple factor this one. Some folk just love the sleek shiny shiny of silver and prefer it over darker metals such as brass or copper. If bling bling is your thing thing, then you might just go for maximum shine time with silver. Personally, I can’t stand the look and smell of copper, and will only use it when no other option is readily available. You, on the other hand, may love the look and smell of copper. It really is down to your own personal taste. However strange that may turn out to be…..
Decision Time !
Having had a quick look at the main influencing factors, you should now have a better idea of things to think about when building or enhancing your mod. At Stealthvape we believe in only ever providing the best products made from the highest grade finest materials. This is why we are offering .99 Solid Silver or C101 Copper Custom or Preformed Contacts and Solder Tabs. You can find them here.
We believe these to be the best options available and are certain that you will agree with us too. We also provide a bespoke design and manufacture and etching service for modders looking to purchase in quantity, offering consultation and help throughout every stage of the process.
Please contact us at sales@stealthvape.co.uk to discuss your options now.
