Spacer thickness and cut change feel of dome - or does it?

1. Effect of Membrane Switch
Construction on Metal Domes

2. Test Objective
Evaluate the effect
– Square Size
– Spacer thickness
– Total Thickness over the
dome
has on the tactile response
of a metal dome

3. Stabilizing The Dome
• Determine correct number of actuations needed to
stabilize a metal dome
– 12.2mm 340g domes tested
• 7 domes tested
• Test Process
– Actuate Dome 1 time
• Test dome on Force Displacement station
– Repeat test 100 times

4. Trip Force Relative to Number of Actuations
344
346
348
350
352
354
356
358
360
362
364
366
0 20 40 60 80 100 120
# of Actuations
Ft[g]
•Trip force Degrades until 20 actuations
•Degradation less than 2% over the next 10 actuations

5. Rebound Force Relative to Number of Actuations
91
96
101
106
111
0 20 40 60 80 100 120
# of Actuations
Fr[g]
•Degrades an average of 3 to 4 grams over 20 actuations
•No degradation for the next 20 actuations

6. Travel Relative to Number of Actuations
0.0200
0.0210
0.0220
0.0230
0.0240
0.0250
0.0260
0 20 40 60 80 100 120
# of Actuations
Dt[in]
•Travel Degrades less than 0.001”

7. Results
• Measurable degradation occurs within the
first 20 actuation
– Maximum degradation less than 2% during
next 10 actuations
• 25 actuations will sufficiently stabilize
metal domes

8. Off Center Actuation
• How Does probe position
effect a dome
– Fixture Designed
• Easy Calibration
– Adjustment in the X
axis
– 0o
and 450
dome
orientations
• Dome centered in
pocket
Calibration Hole
450
00

9. Actuation Test Process
• 12.2mm 340g domes
• Fixture Set-up and calibrated
• Start out with dome centered
• Offset 0.005” increments
• Test at 0 and 45 degrees

10. Trip Force Relative to Offset
150.0
200.0
250.0
300.0
350.0
400.0
450.0
0.000 0.020 0.040 0.060 0.080 0.100 0.120
Offset [in]
Ft[g]
•Slight variation up to 0.040” Offset
•On average variation is 4-6 grams

11. Trip Force Relative to Offset
150.0
200.0
250.0
300.0
350.0
400.0
450.0
0.000 0.020 0.040 0.060 0.080 0.100 0.120
Offset [in]
Ft[g]
Rotation 45o
•Follows same trend as 00
rotation
•Climbs after 0.060” offset

12. Rebound Force Relative to Offset
50.0
100.0
150.0
200.0
250.0
300.0
350.0
0.000 0.020 0.040 0.060 0.080 0.100 0.120
Offset [in]
Fr[g]
•Similar results as trip force up to 0.040” offset
•Climbs to 3 times original value
•Very poor tactile ratio
Rotation 0o

13. Rebound Force Relative to Offset
50.0
100.0
150.0
200.0
250.0
300.0
350.0
0.000 0.020 0.040 0.060 0.080 0.100 0.120
Offset [in]
Fr[g]
Rotation 45o
•Follows identical trend up to 0.040” offset
•Climbs quicker than 00
rotation after 0.040” offset

14. Travel Relative to Offset
0.0100
0.0120
0.0140
0.0160
0.0180
0.0200
0.0220
0.0240
0.0260
0.0280
0.0300
0.000 0.020 0.040 0.060 0.080 0.100 0.120
Offset [in]
Dt[in]
•Least affected trait
•Identical trend for 00
or 450
orientation
•00
shown
•Travel remains constant until an offset of 0.100”

15. Results
• 0.040” offset without significant change
– Same result for 450
or 00
• After 0.040” offset performance altered
• Travel is the least affected trait

16. Switch Test Fixture
•Designed for accurate switch indexing
•Pin index on 1.00” centers
•Index accuracy of 0.003”
•Pin register membrane switch

17. Dome Selection
• Use 12.2mm 340g domes
– From the same lot
• Each dome assigned a switch and a placement
number
– Each Dome Stabilized and tested prior to
assembly
Trip Force (g) Rebound Force (g) Travel (in.) Click Ratio(%)
AVG 335.96 94.42 0.02421 71.89
MAX 351.00 118.30 0.02480 75.01
MIN 322.10 81.90 0.02360 65.27
STD 4.92 4.62 0.00026 1.36
Results

18. Switch Build-up
.
Switch Layer
Dome
Adhesive Spacer
Thickness Over The Dome

19. Testing Square Size
• 20 switches each
– Overlay thickness 0.003”
• 0.007” spacer thickness
– Square sizes 0.390” – 0.460”
» 0.010” increments
» 2 squares per size
– Overlay thickness 0.012”
• 0.007” spacer thickness
– Square sizes 0.390” – 0.460”
» 0.010” increments
» 2 squares per size

20. Trip Force Based on Square Size
Square Size
Unassembled Domes
AVG Trip Force (g)
Assembled Domes
AVG Trip Force (g) Change in Force (g)
0.390" 336.02 332.19 -3.83
0.400" 335.65 330.85 -4.81
0.410" 334.69 330.89 -3.79
0.420" 336.72 330.93 -5.79
0.430" 336.10 330.95 -5.15
0.440" 335.05 330.51 -4.54
0.450" 335.19 331.07 -4.12
0.460" 335.14 331.04 -4.11
Thickness Over the Dome = 0.003"
Square Size
Unassembled Domes
AVG Trip Force (g)
Assembled Domes
AVG Trip Force (g) Change in Force (g)
0.390" 336.02 317.87 -16.09
0.400" 335.65 321.06 -14.24
0.410" 334.69 316.22 -16.61
0.420" 336.72 313.70 -22.94
0.430" 336.10 316.44 -17.05
0.440" 335.05 316.99 -17.29
0.450" 335.19 316.48 -16.92
0.460" 335.14 315.76 -19.15
Thickness Over the Dome = 0.012"

21. Rebound Force Based on Square Size
Square Size
Unassembled Domes
AVG Rebound Force (g)
Assembled Domes
AVG Rebound Force (g) Change in Force (g)
0.390" 94.42 108.37 13.95
0.400" 93.98 105.89 11.91
0.410" 94.52 107.49 12.97
0.420" 94.11 106.86 12.75
0.430" 93.76 106.21 12.45
0.440" 94.51 106.47 11.97
0.450" 93.39 105.75 12.36
0.460" 93.71 105.56 11.85
Thickness Over the Dome = 0.003"
Square Size
Unassembled Domes
AVG Rebound Force (g)
Assembled Domes
AVG Rebound Force (g) Change in Force (g)
0.390" 94.42 169.16 75.94
0.400" 93.98 172.75 79.42
0.410" 94.52 171.17 79.16
0.420" 94.11 169.84 75.45
0.430" 93.76 173.96 78.82
0.440" 94.51 169.32 73.33
0.450" 93.39 166.81 74.06
0.460" 93.71 169.41 77.76
Thickness Over the Dome = 0.012"

22. Click Ratio Based on Square Size
Square Size
Unassembled Domes
AVG Click Ratio (%)
Assembled Domes
AVG Click Ratio (%) Change in Ratio (%)
0.390" 72.08 67.03 -4.87
0.400" 72.17 68.76 -3.23
0.410" 72.34 66.88 -4.87
0.420" 71.95 67.80 -4.23
0.430" 71.46 67.42 -4.67
0.440" 71.26 66.76 -5.01
0.450" 72.18 67.95 -4.19
0.460" 72.62 67.11 -4.92
Thickness Over the Dome = 0.003"
Square Size
Unassembled Domes
AVG Click Ratio (%)
Assembled Domes
AVG Click Ratio (%) Change in Ratio (%)
0.390" 72.08 46.77 -25.32
0.400" 72.17 46.21 -25.96
0.410" 72.34 45.86 -26.48
0.420" 71.95 45.87 -26.08
0.430" 71.46 45.01 -26.45
0.440" 71.26 46.59 -24.67
0.450" 72.18 47.31 -24.87
0.460" 72.62 46.35 -26.27
Thickness Over the Dome = 0.012"

23. Travel Based on Square Size
Square Size
Unassembled Domes
AVG Travel (in)
Assembled Domes
AVG Travel (in) Change in Travel (in)
0.390" 0.02000 0.02000 -0.00041
0.400" 0.02420 0.02368 -0.00057
0.410" 0.02000 0.02000 -0.00051
0.420" 0.02419 0.02426 -0.00007
0.430" 0.02418 0.02414 -0.00004
0.440" 0.02412 0.02375 -0.00037
0.450" 0.02358 0.02399 0.00041
0.460" 0.02417 0.02372 -0.00045
Thickness Over the Dome = 0.003"
Square Size
Unassembled Domes
AVG Travel (in)
Assembled Domes
AVG Travel (in) Change in Travel (in)
0.390" 0.02000 0.02058 -0.00366
0.400" 0.02420 0.02046 -0.00382
0.410" 0.02000 0.02038 -0.00378
0.420" 0.02419 0.02037 -0.00383
0.430" 0.02418 0.02042 -0.00390
0.440" 0.02412 0.02070 -0.00339
0.450" 0.02358 0.02054 -0.00354
0.460" 0.02417 0.02054 -0.00358
Thickness Over the Dome = 0.012"

24. Outcome
• Square size had no effect
– Why?
• Poor lamination
• Poor adhesive bonds
• Overlay Thickness
– No effect on square sizes
• Poor lamination
• Poor adhesive bonds
– Did change dome performance
• Due to preload
– Changed with overlay thickness

25. Testing Spacer Thickness
• 0.003” overlay thickness
– Spacer thickness
• 0.007” – 5pcs
• 0.009” – 5pcs
• 0.011” – 5pcs
• 0.015” – 5pcs
• 0.012” overlay thickness
– Spacer thickness
• 0.007” – 5pcs
• 0.009” – 5pcs
• 0.011” – 5pcs
• 0.015” – 5pcs

26. Trip Force Based on Spacer Thickness
Spacer Thickness
Unassembled Domes
AVG Trip Force (g)
Assembled Domes
AVG Trip Force (g) Change in Force (g)
0.007" 335.44 331.25 -4.19
0.009" 336.52 333.08 -3.44
0.011" 335.81 334.17 -1.63
0.015" 336.11 336.00 -0.10
Thickness Over the Dome = 0.003"
Spacer Thickness
Unassembled Domes
AVG Trip Force (g)
Assembled Domes
AVG Trip Force (g) Change in Force (g)
0.007" 335.44 307.12 -28.33
0.009" 336.52 312.33 -24.19
0.011" 335.81 319.30 -16.51
0.015" 336.11 327.81 -8.29
Thickness Over the Dome = 0.012"

27. Rebound Force Based on Spacer Thickness
Spacer Thickness
Unassembled Domes
AVG Rebound Force (g)
Assembled Domes
AVG Rebound Force (g) Change in Force (g)
0.007" 94.37 107.67 13.30
0.009" 94.50 109.16 14.65
0.011" 94.83 108.70 13.87
0.015" 94.01 110.01 16.00
Thickness Over the Dome = 0.003"
Spacer Thickness
Unassembled Domes
AVG Rebound Force (g)
Assembled Domes
AVG Rebound Force (g) Change in Force (g)
0.007" 94.37 161.66 67.28
0.009" 94.50 164.52 70.09
0.011" 94.83 174.48 79.65
0.015" 94.01 196.64 102.63
Thickness Over the Dome = 0.012"

28. Click Ratio Based on Spacer Thickness
Spacer Thickness
Unassembled Domes
AVG Click Ratio (%)
Assembled Domes
AVG Click Ratio (%) Change in Ratio (%)
0.007" 71.87 66.92 -4.94
0.009" 71.88 66.69 -5.19
0.011" 71.72 67.26 -4.46
0.015" 72.03 67.24 -4.78
Thickness Over the Dome = 0.003"
Spacer Thickness
Unassembled Domes
AVG Click Ratio (%)
Assembled Domes
AVG Click Ratio (%) Change in Ratio (%)
0.007" 71.87 47.36 -24.51
0.009" 71.88 47.32 -24.56
0.011" 71.72 45.35 -26.37
0.015" 72.03 40.00 -32.02
Thickness Over the Dome = 0.012"

29. Travel Based on Spacer Thickness
Spacer Thickness
Unassembled Domes
AVG Travel (in)
Assembled Domes
AVG Travel (in) Change in Travel (in)
0.007" 0.02407 0.02229 -0.00178
0.009" 0.02442 0.02156 -0.00265
0.011" 0.02427 0.02166 -0.00261
0.015" 0.02427 0.02128 -0.00299
Thickness Over the Dome = 0.003"
Spacer Thickness
Unassembled Domes
AVG Travel (in)
Assembled Domes
AVG Travel (in) Change in Travel (in)
0.007" 0.02407 0.02080 -0.00327
0.009" 0.02442 0.02050 -0.00371
0.011" 0.02427 0.02046 -0.00381
0.015" 0.02427 0.01957 -0.00470
Thickness Over the Dome = 0.012"

30. Trip force Relative to Spacer and Overlay Thicknesses
300
320
340
360
380
400
0.005 0.007 0.009 0.011 0.013 0.015 0.017
Spacer Thickness (in)
TripForce(g)
0.003” Overlay
0.012” Overlay
•There are trends relating switch construction and performance
•Straight line profile exists
•Spacer size has less impact using thin overlays
•Suggests that trip force can be estimated for switch construction

31. Rebound Force Relative to Spacer and Overlay Thickness
100
120
140
160
180
200
0.005 0.007 0.009 0.011 0.013 0.015 0.017
Spacer Thickness (in)
ReboundForce(g)
0.003” Overlay
0.012” Overlay
•Rebound force exhibits much the same trend.
•Rebound force effected greater by overlay and spacer thickness
•Straight line trend also exists

32. Click Ratio Relative to Spacer and Overlay Thickness
35
40
45
50
55
60
65
70
0.005 0.007 0.009 0.011 0.013 0.015 0.017
Spacer Thickness (in)
ClickRatio(%)
0.012” Overlay
0.003” Overlay
•Given the trip and rebound forces, click ratio follows the same trend

33. Outcome
• Spacer thickness had an effect
– Rebound force influenced more than trip forces
• Spacer thickness effect preload
• Trends exist
• Overlay thickness amplify effects of spacer
thickness
• Thickness effects preload
• Rebound force and click ratio most effected by
change

34. Conclusions
• Square size had no effect
– For this construction
• With a thin spacer
– Having poor lamination
» Poor adhesive bonds
• Spacer thickness effected performance
– Pre-load changed
• Magnitude of results
– Affected by construction

35. • Overlay thickness impacts performance
– Thicker overlays create stronger preloads
– Thicker overlays with thicker spacers create
stronger rebound forces
– Effect of overlay thickness not altered by
square size
• When using thin spacer
– With poor lamination
» Poor adhesive bonds
Conclusions

36. Special Thanks to Name Plates
For industry and Automation
Alternatives for help with
material processing