Open two pogo pin datasheets and you may find one quoting gold in “microinches” and the other in “microns.” Same metal, same job, two unit systems. If you convert one wrongly, you can end up paying for plating you don’t need, or ordering plating that wears through before your product ships its first update.
This guide explains the units in plain language, shows how gold thickness affects wear, corrosion and contact resistance, and gives you a checklist for writing the plating line on a drawing or quote request. It supports our page on waterproof pogo pin and magnetic connectors for 5A to 30A designs, where plating choices matter most.
Quick answer: A microinch (µin) is one millionth of an inch. A micron (µm) is one millionth of a metre. One microinch equals 0.0254 microns, and one micron equals about 39.37 microinches. Both measure the thickness of the gold layer on a pogo pin’s plunger and barrel.
- Thicker gold generally lasts longer under repeated mating and resists corrosion better, but it costs more.
- Gold is plated over nickel, and both layers matter.
- There is no single “right” thickness. It depends on mating cycles, environment, current and budget.
Microinches vs. Microns: What the Units Mean
Plating thickness is tiny, which is why two units exist. North American suppliers often quote microinches (written µin, or “u-inch” when the Greek letter is hard to type). Most of the rest of the world uses microns (µm). The measurements are the same physical quantity, just expressed in different systems.
The conversion is simple: multiply microinches by 0.0254 to get microns, or multiply microns by 39.37 to get microinches. A gold layer of 30 µin is therefore about 0.76 µm. For scale, a human hair is roughly 70 µm across, so even a thick pogo pin gold layer is far thinner than a hair.
| Microinches (µin) | Microns (µm) |
|---|---|
| 5 | 0.127 |
| 10 | 0.254 |
| 15 | 0.381 |
| 30 | 0.762 |
| 50 | 1.270 |
| 100 | 2.540 |
Here is the trap buyers fall into. A “mil” is a thousandth of an inch, and a microinch is a thousand times smaller than that. Mixing up µin with mil, or reading “0.125” as microinches when the drawing means microns, creates a 40-times error. Always write the unit next to the number, and if a drawing leaves it out, ask before you quote.
Why Pogo Pins Use Gold Over Nickel
Pogo pin plating is a stack, not a single layer. A typical contact starts with a brass or copper-alloy base, receives a nickel underplate, and finishes with a gold topcoat. CFE’s datasheets describe the plunger and barrel this way: brass, gold over nickel, with the plating specification adjustable to customer requirements.
Each layer has a job. Gold is the contact surface because it resists tarnish and keeps contact resistance low and stable. ASTM’s specification for electrodeposited engineering gold lists corrosion and tarnish resistance, low and stable contact resistance, bondability, and solderability among the reasons gold is used. Nickel sits underneath as a barrier. Without it, copper and zinc from a brass base can migrate toward the surface over time and cause tarnish, which defeats the purpose of using gold.
Gold type matters as well. Engineering gold comes in different purities and hardnesses. Softer, purer gold is good for soldering and bonding. Harder gold, usually alloyed with a small amount of another metal, holds up better to sliding wear. ASTM B488 organises coatings by type (purity) and code (Knoop hardness), so a drawing can name both. For a spring-loaded contact that scrapes across a pad thousands of times, hardness is as important as thickness.
The takeaway: when someone says “gold plated pogo pin,” ask three follow-up questions. How thick is the gold? What is under it? What type of gold is it? A pin with a thin, soft finish over no barrier is a very different product from one with a controlled nickel layer and a harder gold topcoat, even though both are “gold plated.”
What Gold Thickness Changes in Real Use
Think of the gold layer as the tread on a tyre. Every time the pin mates, the plunger tip rubs against its pad, and a little tread wears away. When the gold is gone, the nickel is exposed. Nickel oxidises, contact resistance rises, and a connector that worked on day one becomes intermittent. More gold means more tread, and more mating cycles before that happens.
Thickness also affects porosity. Very thin gold can contain microscopic pores that let moisture and corrosive gases reach the layer below. In a dry office product this rarely matters. In a sweaty wearable, a humid vehicle interior or a product that gets rinsed, pores become corrosion paths. Thicker gold, plus a good nickel layer, closes more of those paths.
| Factor | Thinner gold | Thicker gold |
|---|---|---|
| Part cost | Lower | Higher |
| Wear life under repeated mating | Shorter | Longer |
| Corrosion resistance | More exposure to pores | Better protection |
| Contact resistance over time | More likely to drift after wear-through | Stays stable longer |
| Best fit | Dry, low-cycle, cost-sensitive products | Frequent docking, humid or wet use, long service life |
Gold is not a cure-all, though. Plating cannot fix a contact that is over-compressed or badly aligned, and a thick gold layer will still wear faster on a pin with excessive spring force. Our guides on why pogo pins fail and what happens when a pogo pin is over-compressed explain the mechanical side of the story.
How CFE Writes Plating on a Datasheet
The clearest way to learn the notation is to read a real one. CFE’s waterproof spring-loaded contact pin, part number BP77031, lists its plunger and barrel as brass with 0.125 µm Au over Ni. In microinches, that is about 4.9 µin, close to what the industry calls a flash layer. The same datasheet lists a rated 12 V, 10 A, a maximum contact resistance of 50 milliohms, and a contact force of 175 g ±20% at 1.8 mm working stroke.
That one line tells an engineer a lot. The unit is microns, the gold is thin, and the base is brass with a nickel layer. It also shows why “gold plated” is incomplete as a specification. CFE’s pin pages state that gold plating can be changed according to customer requirements, so a standard datasheet value is a starting point for your application rather than a ceiling.
If you are comparing suppliers, convert everything to the same unit before you compare price. A quote for “0.5 µm gold” and one for “10 µin gold” look unrelated until you realise 0.5 µm is about 20 µin, which is twice as much gold. The cheaper quote may simply be the thinner one.
Choosing Gold Thickness by Application
There is no universal number, but there is a sensible way to think about it. Start from how the product will be used, estimate how many times the contact will mate over its life, and then ask which failure would hurt most: wear, corrosion, or cost.
| Use case | What drives the choice | Plating direction |
|---|---|---|
| Occasional charging in a dry home product | Low cycle count, cost pressure | Thinner gold may be enough; confirm with a cycle test |
| Daily docking (earbuds, watches, handheld devices) | Thousands of cycles, sweat and skin oils | Thicker, harder gold over a solid nickel layer |
| Outdoor, automotive or wet environments | Moisture, temperature swings, vibration | Thicker gold with low porosity, plus a sealed design |
| High-current power contacts | Stable low resistance, heat | Plating spec agreed with engineering alongside spring force and current |
A practical tip: ask for quotes at two plating levels. The price difference is often small next to the cost of a field failure, and having both numbers lets your team decide with real data. For more on how plating and other choices move the price, see what drives the price of a custom pogo pin connector.
Gold Plating in High-Current and Waterproof Designs
Plating matters more as current rises. Heat in a contact follows P = I² × R, so a small increase in contact resistance becomes a large increase in heat at 20A or 30A. When gold wears through and nickel oxidises, resistance climbs, the contact warms, and the problem feeds itself. That is why high-current pins deserve a deliberate plating decision rather than a default one. Our article on why 4 × 5A pogo pins don’t make a 20A connection goes deeper on resistance and heat.
Wet environments add another wrinkle. If powered contacts get wet, current can flow through the water and corrode the positive contact quickly, and extra gold thickness alone will not stop that. The better fix is electrical: keep the pins unpowered until the circuit confirms a proper mate. CFE’s guide on why powered pogo pin contacts corrode in water explains the mechanism. Plating is one layer of defence, and good design is the other.
If your product needs both sealing and current, review the waterproof pogo pin range and the 5A-30A high current pogo pins. After you pick a part, confirm the real-world result with the steps in how to test a waterproof pogo pin connector.
How to Specify Plating on a Drawing or Quote Request
Most plating confusion comes from vague wording. Copy this checklist into your RFQ so the supplier can quote the right thing the first time.
- Gold thickness with a unit, such as “0.5 µm (about 20 µin) minimum.”
- Underplate: nickel, and its thickness if you have a requirement.
- Gold type: soft or hard, and any standard you work to, such as ASTM B488 types and codes.
- Where the plating applies: plunger, barrel, or both.
- Mating cycles the contact must survive, and the mating surface it touches.
- Environment: humidity, sweat, washdown, temperature range, and whether the contacts are powered when exposed.
- Current and acceptable contact resistance at end of life, not just at day one.
- Inspection method: how thickness will be measured and how many pieces are sampled.
The standard behind many of these terms is ASTM B488, the specification for electrodeposited gold coatings for engineering uses, which covers purity, hardness, thickness, adhesion and porosity. Standards are revised over time, so check the current edition before you cite it on a drawing. For our own process controls, see the CFE quality page.
Frequently Asked Questions
How do I convert microinches to microns?
Multiply microinches by 0.0254. For example, 30 µin is 0.762 µm. To go the other way, multiply microns by 39.37.
Which is thicker, 0.1 µm or 5 µin?
0.1 µm is about 3.9 µin, so 5 µin (0.127 µm) is slightly thicker. Always convert to one unit before comparing quotes.
Is thicker gold always better on a pogo pin?
Not always. Thicker gold usually improves wear life and corrosion resistance, but it raises cost. If your product mates a few hundred times in a dry setting, extra gold may add price without adding value. Match the thickness to cycles and environment.
Why is nickel used under gold?
Nickel acts as a barrier between the brass base and the gold. It slows the migration of base metals to the surface and gives the gold a hard, smooth foundation. If the gold wears away, the nickel is what remains exposed.
Can CFE change the gold plating on a standard pogo pin?
Yes. CFE’s pin pages state that gold plating can be adjusted to customer requirements. Send your thickness, cycle life and environment through our custom pogo pin connector page or the contact form.
Get the Plating Right Before You Order
If you are unsure whether your design needs 5 µin or 50 µin, you don’t have to guess. Send your current, mating cycles and operating environment to cfe@cfeconn.com, or request a quote and samples. Our engineers can recommend a plating level and quote two options so you can compare cost against life. You can also start from the waterproof 5A–30A connector page to see the full range.
