What Makes a Pogo Pin High Precision?
Start with two views of the contact. In the top view, locate the tip center relative to the mounting features and compare its profile with the exposed pad. In the side view, measure the unloaded tip height and the mated pad height from the same seating plane. The difference is the working compression. Measuring from the end of a locating peg instead of the seating plane introduces an error equal to the peg length.
Harwin's P70-2100045R illustrates how to read a real drawing. It is a surface-mount spring contact with a rounded head and a locating peg. Its customer drawing gives the following dimensions and inspection references.
| Feature | Published dimension or requirement | How to inspect it |
|---|---|---|
| Head diameter | 0.90 mm nominal, ±0.10 mm under the drawing's general tolerance | Measure the finished head optically. Check its center position separately after mounting. |
| Free height above the seating plane | 5.50 mm nominal, ±0.10 mm under the general tolerance | Seat the part on its mounting face and measure to the unloaded tip without depressing it. |
| Working height | 4.50 mm normal, with stated working limits of 4.20 to 4.70 mm | Measure from the same seating plane to the mating surface with the assembly closed. |
| Contact force | 0.68 ±0.24 N at normal working height | Compress the contact to a height of 4.50 mm and record the axial force. |
At nominal dimensions, the pin compresses 1.00 mm at its normal working height. The minimum working height identifies the lower end of the permitted operating range. A mechanical stop inside the pin, if reached, is a separate limit and should not set the dock's closed position.
The drawing also illustrates an important distinction in procurement. 5.40 to 5.60 mm is the permitted free-height interval. To learn how closely a production lot actually holds that dimension, request the measured minimum and maximum, sample count, lot number, and measurement method. A catalog drawing supplies the acceptance limits. A sample inspection report supplies the observed range.
How Does Pin Precision Affect a Multi-Pin Connector?
Pitch determines the spacing between pins. The housing determines where the row lands. A four-pin row can have the correct adjacent pitch and still miss its pads if the entire row sits too far from a locating feature. A small rotation can move the outermost tips farther than those near the center. Inspect the tip coordinates relative to the housing datums that locate the connector in the device. Give particular attention to the two end positions.
Tip height also needs checking after assembly. Measure every unloaded tip from the common mounting plane and record both its absolute height and the difference between the highest and lowest tips. Four equally high tips can all sit too low if the contacts are seated too deeply. At the largest assembled gap, check whether the shortest pin develops the required contact force. At the smallest gap, check whether the tallest pin stays within its permitted working range.
The forces add up. Four P70-2100045R contacts, each at the specified 4.50 mm working height, would exert a calculated nominal total of 2.72 N. Using the upper stated force of 0.92 N per contact gives 3.68 N at that same height. In a magnetic dock, measure the available holding force at the actual separation of the magnetic parts, with the cover and any seals installed. Check that both ends of the dock seat fully. A magnet can hold the device in place while one end of the contact row remains lightly compressed.
How Do You Verify Pogo Pin Connector Quality?
| Verification | Evidence to request | What to check |
|---|---|---|
| Dimensions and position | Revision-controlled drawing and a dimensional report for the assembled connector | Tip locations relative to the mounting datums, unloaded height at each position, and sample minimum and maximum values |
| Contact force | Force-versus-travel curve or readings at specified heights | Whether the test covers the device's installed gap range, especially the position with the least compression |
| Electrical performance | Contact resistance, loaded voltage drop, and terminal temperature-rise records | Voltage-sense points, current per contact, number of energized contacts, local ambient temperature, and PCB or wire configuration |
| Mating life | Resistance and force readings before and after cycling, with wear records for both mating surfaces | Mating material and finish, stroke, sample count, cycle count, electrical load during mating, and failure criteria |
A contact-resistance figure is only comparable when the measurement endpoints agree. A four-wire measurement across a mated pin and pad answers a different question from a voltage reading between a cable plug and a device PCB. The latter includes intervening conductors and joints. Both readings can be useful. Marking the endpoints makes it possible to tell whether a change comes from the contact or elsewhere in the charging path.
Which Manufacturing Checks Keep Production Consistent?
After machining and plating, inspect the tip profile, barrel bore, and plunger dimensions that control sliding clearance. The drawing should identify which limits apply to the finished, plated part. Check return movement through the intended working stroke as well. A plunger can reach the correct free height when new yet stick at a particular point during release.
After housing assembly, locate the finished connector by its production mounting features. Measure each tip's position and height, compress and release the row, and verify terminal retention using the specified method. This stage reveals defects that loose-pin inspection cannot detect, including a tilted terminal, unequal seating depths, or a correctly spaced row shifted relative to the mounting pegs.
At shipment, tie the inspection record to the part number, drawing revision, and packaging lot code. If a supplier reports that height or position has stayed consistent across several lots, ask how many lots and parts the figures cover. Keep the measurement fixture and reference plane in the record. Otherwise, a change in how the inspector holds the connector can look like a change in production.
Design Example: Selecting a Pogo Pin for a Compact Charging Dock
Consider an illustrative four-contact dock with 1.60 mm diameter exposed pads, 0.20 mm maximum lateral offset, and a closed gap ranging from 4.30 to 4.80 mm. The design requires the entire projected tip outline to stay over the exposed pad. Harwin's P70-2100045R provides a standard candidate with published dimensions that can be checked before ordering samples.
At the upper drawing limit, the head is 1.00 mm in diameter. On a 1.60 mm circular pad, the fully contained head can move (1.60 − 1.00) ÷ 2 = 0.30 mm from center. If the stated 0.20 mm offset includes all lateral errors, the design has 0.10 mm of edge clearance at its worst position. If that offset covers only movement between the two housings, PCB placement and pin-position tolerances still have to come out of the remaining allowance.
The axial check changes the decision. The dock's 4.80 mm maximum gap exceeds the pin's 4.70 mm maximum working height by 0.10 mm. The tip may still touch the pad there, but the design cannot rely on the manufacturer's specified working range at that position. A different head profile would do little to correct this particular mismatch. The relevant options are to reduce the closed-gap variation, revise the connector seating position while checking clearance at the opposite limit, or select a contact with a suitable working-height range.
Once a candidate meets both drawing checks, test it in the dock at center and maximum offset. Record the contact marks, voltage drop across the positive and return paths, and terminal temperature rise at the intended charging current. Repeat after the required mating cycles. These measurements decide whether the geometric clearance is sufficient in service. The dimensions above are a design calculation, not measured charging performance.
What Should Buyers Specify Before Requesting Samples?
Send drawings of both mating parts. Identify the features that align them, exposed pad dimensions and finish, minimum and maximum closed gaps, permitted tilt, and total lateral offset. If a dimension is fixed because the PCB or enclosure is already in production, mark it on the drawing.
For each pin position, state its function, continuous current, peak current and duration, and which neighboring contacts carry current at the same time. Include the operating environment, expected mating cycles, and any limit on visible pad wear. Agree in advance on the dimensional limits, force at the installed height, maximum loaded voltage drop, and permissible temperature rise that determine sample acceptance.
For a drawing-based review, Dongguan Xinteng Electronics Co., Ltd. can assess whether a standard contact fits the assembly or whether the head profile, free height, pin position, or housing location needs to change. Carry the approved dimensions, tolerances, and test conditions into the production drawing so later shipments can be checked against the same requirements as the samples.
Technical References
Harwin. SMT Spring Loaded Contact with Location Peg. Customer information drawing P70-2100045X, Issue 4, sheet 1 of 1. Covers part P70-2100045R.
International Electrotechnical Commission. IEC 60512-2-1:2002. Connectors for electronic equipment - Tests and measurements - Part 2-1: Electrical continuity and contact resistance tests - Test 2a: Contact resistance - Millivolt level method.
