PCB Contact Design Guide

PCB Contact Design: SILICONE RUBBER KEYPADS & CONDUCTIVE RUBBER KEYPADS

Northpoint Technologies, Inc. is among the top printed circuit board (PCB) manufacturing companies in the USA as well as manufacturing capabilities in Mexico and China. We are a PCB with components manufacturer that provides turnkey service, custom design, Prototype PCB manufacturing, thin PCB manufacturing, double layer PCB manufacturing, and multi-layer PCB manufacturing. PCB boards, which are used in all but the most simple electronic products, require additional design. Large quantities can be produced at one time once the layout is complete.

Typical Gold or Nickel Plated Board Contact Designs

np_pcbcont_02 np_pcbcont_03 np_pcbcont_04 np_pcbcont_01

Typical Carbon Screened Board Contact Designs

np_pcbcont_07 np_pcbcont_05 np_pcbcont_06

These designs are for reference only. There is no preferred contact design. As a PCB assembly manufacturer Northpoint Technologies, Inc. provides as many contact paths as possible to achieve the best switch operation in production parts PCB manufacturing.

Carbon contacts are typically round, with standard sizes in 2, 2.5, 3, 3.5, 4, 5, 6, 7, and 8 mm diameter. Other shapes and sizes are available.

The PCB electrode should be 1.25 times the size of the carbon contact on the bottom of the key.

If contact resistance of less than 50 ohms is required, a metal contact can be used instead of a carbon contact. The metal contact is molded to the keypad in the same way as the carbon contacts. Contact resistance using the metal contacts is typically less than 15 ohms. Metal contacts are seldom used in rubber keypads because of the high cost and long lead times associated with metal contacts.

Specification
Gold Plating
Nickel Plating
Carbon Screen Contact
Plating:
min. 3 micro inches over 60 micro inches of nickel
min. of 100 micro inches
.001″ over copper traces
Trace Width:
0.25-0.40 mm
0.25-0.40 mm
Minimum distance
between traces:
0.30mm
0.30mm
0.50 mm
Maximum distance
between traces:
0.40 mm
0.40 mm
Electrical contact
resistance:
less than 100 ohms
less than 100 ohms
600-1000 ohms