Fact 1. Barrel Diameter and Pin Pitch Describe Different Dimensions
Barrel diameter is the outside diameter of one pin body. Pitch is the distance between the centerlines of adjacent pins. The barrel, flange, and solder footprint determine how much board space each pin occupies. Pitch determines whether the pins line up with the mating pads.
Consider a two-pin earbud case. Two candidate pins can have identical barrel diameters but different tip diameters. On a 1.20 mm-wide pad, a centered 0.60 mm tip has 0.30 mm of clearance on each side. A 0.25 mm sideways shift leaves only 0.05 mm on the nearer side. This simple drawing check assumes the entire tip outline must stay within the pad. Check both pads with the earbud rotated as far as the charging well allows.
Fact 2. Free Height Minus Working Height Gives the Working Stroke
Working stroke = free height − installed working height. Measure both heights along the pin axis from the same mounting surface.
As a calculation example, a pin with a free height of 3.00 mm compresses 0.60 mm when its mating pad sits 2.40 mm above the mounting surface. If the installed gap varies from 2.30 to 2.50 mm, compression ranges from 0.50 to 0.70 mm before accounting for the pin's own height tolerance.
Check the shortest pin at the largest gap for sufficient contact force. Check the tallest pin at the smallest gap against the model's permitted operating stroke. A through-hole solder tail below the mounting surface contributes to overall part length but does not increase the tip height available above the board.
Fact 3. Contact Force Has Meaning Only at a Specified Compression
The CPG-16-SMT-B datasheet specifies 25–55 gram-force (gf), typically 40 gf, at a 2.50 mm working height. It also lists a 0.50 mm mid stroke and a 0.55 mm full stroke. The 0.60 mm compression in the calculation above would exceed this particular pin's full stroke.
For a magnetic charging dock, add the forces of all pins at their actual installed heights. Two parallel pins at 40 gf each exert about 80 gf against the device. Check that the magnets hold the device fully seated even with higher-force samples. If one side lifts, a pin on the opposite side may lose compression despite meeting its individual specification.
Fact 4. Current Capacity Depends on More Than Pin Size
A current rating needs test conditions. Check ambient temperature, mounting method, allowable temperature rise, and how many neighboring contacts carry current. For a pulse load, record its duration and repetition rate.
A published low-profile spring-contact test illustrates the difference between a component rating and an assembly result. Three contacts were tested individually at half stroke against a gold-plated target. At 2 A and 20°C ambient, the measured plunger temperatures ranged from 25°C to 27°C. A closed charging case with both supply and return contacts energized has different heat paths.
On the assembled case, measure voltage drop from each pin's solder terminal to its mating pad under load. Add the supply and return drops to find the loss across the connector pair. Measuring from the power adapter to the device instead includes cable and board losses as well.
Fact 5. The Mating Surface Guides the Choice of Tip and Finish
A rounded tip is a practical starting point for a flat charging pad that sees daily docking. Check the landing point at maximum offset and inspect both surfaces after cycling. A wear track running off one edge of the pad is a reason to check the housing guides before changing the plating.
A PCB test fixture has different priorities. A pointed tip may penetrate a light surface film, while a crown tip offers several contact edges on a soldered target. Compare first-attempt contact success, allowable probe-mark depth, and debris buildup over the intended cleaning interval.
Read a "gold-plated" claim alongside the contact-area thickness and the mating-pad finish. For a cycle-life claim, look for the mating material, test stroke, electrical load during mating, and the resistance or mechanical limit used to define failure.
Fact 6. A Pin That Fits the PCB Still Needs an Assembly Check
For a surface-mount pin, verify the land pattern, pickup method, and pin verticality after reflow. For a through-hole pin, verify the finished hole diameter, solder-tail dimensions, and the surface that sets the installed height.
On an assembled sample, press and release every plunger, measure its free height, and inspect its mark on the mating pad. Record the results by pin position. An array average can hide the one low or tilted contact responsible for intermittent charging.
Miniature Pogo Pin Selection Checklist
| Selection question | Record to keep |
|---|---|
| Will the pins fit and land on their pads? | Barrel and tip diameters, pitch, pad dimensions, mounting drawing, and worst-case offset |
| How far will each pin compress? | Free-height tolerance, minimum and maximum installed gaps, and permitted working stroke |
| Will the device stay seated? | Force at each working position, combined spring force, and latch or magnet arrangement |
| Can the connection carry the actual load? | Continuous and peak current, pulse duration, loaded voltage drop, temperature rise, and measurement locations |
| What changes after repeated use? | Mating finish, cycling conditions, resistance before and after cycling, and wear on both surfaces |
| Which product do the results cover? | Part number, drawing revision, sample count, supplier ratings, and measurements from the finished assembly |
Technical References
CPG-16-SMT-B Pogo Pin Datasheet. Revision 1.0, November 4, 2024. Mechanical drawing, working height, stroke, and contact-force specifications.
Spring Loaded Contact: Specifications, Mechanical & Climatic Tests. Version 2.0, October 2005. Test T13 and Group III current-carrying capacity results.
