PCB Contact Design Guide

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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 based in California and 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.

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.

Typical Gold or Nickel Plated Board Contact Designs
Nickel Plated
Nickel Plated
Nickel Plated
Nickel Plated
Typical Carbon Screened Board Contact Designs
Carbon Screened Board
Carbon Screened Board
Carbon Screened Board

    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.

    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