A magnetic charging connector carrying 3 A, 5 A or 10 A has to do more than make contact. It must carry the specified current without excessive voltage drop or heating, including after repeated mating and wear. The most demanding point may be the small interface where a pogo pin meets its pad, rather than the bulk metal inside the pin.
The original figures should be treated with care. There is no universal rule that a 5 A connector needs a particular gold thickness, that every pin should be limited to 2 to 3 A, or that a connector passes simply because its temperature rise stays below 30°C. Those requirements depend on the complete assembly and the conditions under which it is rated.
Find the resistance before choosing the metal
Heat generated in a contact path follows \(P = I^2R\). If one part of the path measures 10 mΩ, it dissipates 0.1 W at 3 A but 1 W at 10 A. That heat may be concentrated in a small connector surrounded by plastic.
The measurement needs to cover the relevant path: the mating interface, the pogo pin's internal contacts, its termination and the corresponding return path. A low-resistance barrel material helps, but it cannot compensate for a pin tip that barely touches its pad. Contact resistance should therefore be checked at the intended working stroke and again after mating cycles and environmental exposure.
Match the conductive material to the part's job
The plunger and barrel need adequate conductivity, mechanical strength and manufacturing consistency. Machinable brass can be suitable for some designs; higher-conductivity copper alloys may be considered where resistance in those parts is a significant source of loss. Material selection should follow measured performance and part geometry, rather than a fixed boundary such as "brass below 5 A, tellurium copper above 5 A."
The spring has a different primary job: maintaining force through the specified stroke and service life. Whether it also carries substantial current depends on the pogo pin's internal construction. In a design that provides another current path between plunger and barrel, a stainless steel spring may serve mainly as a mechanical element. Calling beryllium copper the required spring material for every high-current pin would overlook that distinction.
Heat can also affect spring force and surrounding materials over time. A design review should consider the maximum operating temperature, expected time at load and whether contact force remains adequate after thermal aging.
Specify gold for contact stability and wear
Gold plating helps keep the mating surface free of insulating oxides. Its main electrical benefit is a stable interface over time; gold does not turn an undersized contact into a high-current one. Current capacity still depends on contact geometry, force, internal resistance and heat dissipation.
A nickel underplate is commonly used beneath gold on copper alloy contacts. It acts as a barrier between the base metal and the gold and forms part of the overall plating specification. For a connector that mates frequently, the gold deposit must also be suitable for repeated contact. A very thin flash finish should not be assumed to provide the same wear life as a specified functional contact finish.
Gold thickness cannot be assigned from amperage alone. A thicker deposit may be needed for a particular wear or corrosion requirement, but 20, 40 or 50 µin is not an automatic threshold for 3 A, 5 A or 10 A. The drawing should identify the required finish at the actual mating areas and distinguish a nominal thickness from a minimum thickness. The mating pad finish belongs in the same review.
Design the contact pair around the available space
Pin diameter, tip shape, pad size and spring force all influence the connection. A shaped tip or more than one contact point may improve performance in a particular design, but a larger apparent contact area does not guarantee lower resistance. The pin must reach its pad and compress within its intended stroke after accounting for housing and assembly tolerances.
Magnetic attraction helps bring the two halves together. It does not replace the spring force at each electrical contact. A stronger magnet grade, such as N52, does not by itself specify the holding force of an assembled connector; magnet size, arrangement, air gap and operating temperature matter. Excessive pull can also make disconnection less suitable for the product.
If several pins share the power or ground path, they should not be assumed to divide current equally. Small differences in contact resistance and compression can load one pin more heavily than its neighbors. The board traces, wires and terminations must carry the total current as well.
For a custom connector, we can use a customer drawing to review pin layout, magnetic alignment, mating travel and available space, then develop pogo pin and magnetic connector samples around the required current and use conditions. The proposed materials and plating can be evaluated on the assembled mating pair before production specifications are fixed.
Test at the rated load
A useful qualification test applies the intended continuous current at the highest specified ambient temperature and measures both voltage drop and temperature at the relevant points. Repeat the measurements after mating cycles, vibration where applicable, and environmental exposure appropriate to the product.
The test should use the production-intent housing, pads, wires and board layout. A pin rated on its own may run hotter once enclosed, and a short laboratory connection may conceal losses in the final assembly. If the connector can be disconnected under load, that operating condition also needs to be addressed in the electrical design.
FAQ
Does a 10 A magnetic connector require 50 µin of gold?
No fixed gold thickness follows from a 10 A rating. The finish should meet the contact's wear and corrosion requirements, while the assembled connector must pass resistance and temperature testing at its rated current.
Is beryllium copper required for the pogo pin spring?
No. The suitable spring material depends on force, temperature, life requirements and whether the spring forms part of the main current path.
Can four parallel pins each rated at 2.5 A carry 10 A?
That cannot be assumed from the individual ratings. Parallel pins may carry unequal currents, and the rest of the connection must also be rated for the load. Test the complete array under its intended conditions.
Will a stronger magnet prevent heating or arcing?
A suitable magnet arrangement helps the connector seat and stay aligned. Heating still depends on electrical resistance and current. If connection or disconnection can occur while power is applied, the circuit and contacts must be evaluated for that condition.
