Application NoteTactile Switch Electrical Height Versus Electrical Travel

Easy Tactile Switch Integration
With the increasing availability of 3D files from manufacturers, placing the various electroniccomponents on a PCB is relatively easy.
It becomes more complicated when integrating electromechanical components such as switches.
Their static installation is just as easy as any other electronic component. Still, it becomes morechallenging when the switch forms an integral part of the Human-Machine Interface and requires aperfectly controlled mechanical actuation. This requirement is further complicated when consideringthat switches can be operated directly by a finger on a button or by levers or toggles.
The total of the tolerance stack must be calculated to guarantee the the switch’s actuation in all
circumstances and its possible protection from overload and/or overtravel.

Figure 1: KSC2 Series

In general, two crieteria are specified by the manufacturers to allow the integration of the switch:

Electrical Travel (Te)Electrical Height (He)The Electrical Travel (Te) ON is defined as the travel of theacutator’s top which is required to reach the electrical switching
point (ON).

The Electrical Height (He) ON is defined as the product height
when the electrical switching point (ON) is reached. The PCB isused as a reference, considering switch terminals in contact with
the PCB (no solder thickness).

Figure 2: Electrical Travel Version

Figure 3: Electrical Height Version

In most cases, the designer will use Electrical Travel, a stack-up analysis, to calculate the position of the electrical switching point using
the top of the PCB as a reference. This method has the disadvantage of cumulating the tolerances of each of the criteria; therefore, it isvery common to obtain tolerances of ±0.4 mm.
It needs to be confirmed that the actuator travel is always long enough to ensure electrical contact, which will expose the switch tosignificant over-travel. Since the position of the switch point could be more precise, the travel and tactile effect in the application will beproportionally affected and could provide a poor overall feel.

Replacing Electrical Travel with Electrical Height
C&K, now part of Littelfuse, redesigned the product’s functional dimensions to facilitate integration and provide even more support
to customers. The product itself and its behaviour remained unchanged but the electrical switching position from the PCB is now
consistently specified with better accuracy due to extensive process controls and improved manufacturing methodologies.

Littelfuse.com

1©2024 Littelfuse Inc.

Application Note
A comparison: Electrical Travel and Electrical HeightFigure 4: Previously: Electrical Travel Te ON

Figure 5: Now: Electrical Height He ON

Numerical approach:Specification:• Product height = 3.5+/-0.2mm• Te ON = 0.5+/-0.2mm
 Equivalent Electrical Height is usually calculated
He ON eq = 3.0+/-0.4mm• Product height = 3.5+/-0.2mm• He ON = 3.0+/-0.2m

Advantages of the Electrical Height• As a general manner, tolerances on:– Product height is ±0.2 mm– Electrical travels are ±0.2 mm (can be ±0.25 mm or ±0.3 mm for high actuation forces).
• In general, designers need to know the switching point position from the PCB and apply the formula:– Product Height ±0.2 mm – Electrical travel ±0.2 mm = Equivalent Electrical Height He ±0.4 mm as a minimum tolerance.
• The target of replacing the Electrical Travel (Te) value by the Electrical Height (He) is to avoid cumulated tolerances and to propose
a functional characteristic with a tighter tolerance.
• Electrical Height (He) is stable , with a standard tolerance of ±0.2 mm. C&K can develop KSC versions on request with exact
tolerances on such dimension: ±0.1 mm or ±0.08 mm.
• Only J terminals are recommended for He versions. No change for G terminals.
• In the same way, Mechanical Travel is replaced by the Mechanical Height.
• Please note that nominal values for both electrical and mechanical travel are still provided within the specifications for information.

Disclaimer Notice - This document is provided by Littelfuse, Inc. (“Littelfuse”) for informational and guideline purposes only. Littelfuse assumes no liability for errors or omissions in this document orfor any of the information contained herein. Information is provided on an “as is” and “with all faults” basis for evaluation purposes only. Applications described are for illustrative purposes only andLittelfuse makes no representation that such applications will be suitable for the customer’s specific use without further testing or modification. Littelfuse expressly disclaims all warranties, whether
express, implied or statutory, including but not limited to the implied warranties of merchantability and fitness for a particular purpose, and non-infringement. It is the customer’s sole responsibility
to determine suitability for a particular system or use based on their own performance criteria, conditions, specific application, compatibility with other components, and environmental conditions.
Customers must independently provide appropriate design and operating safeguards to minimize any risks associated with their applications and products.
Littelfuse products are not designed for, and shall not be used for, any purpose (including, without limitation, automotive, military, aerospace, medical, life-saving, life-sustaining or nuclear facility
applications, devices intended for surgical implant into the body, or any other application in which the failure or lack of desired operation of the product may result in personal injury, death, or property
damage) other than those expressly forth in applicable Littelfuse product documentation. Littelfuse shall not be liable for any claims or damages arising out of products used in applications not expressly
intended by Littelfuse as set forth in applicable Littelfuse documentation.

Read complete Disclaimer Notice at www.littelfuse.com/disclaimer-electronics
Littelfuse.com2©2024 Littelfuse Inc.