effect of membrane switch construction on metal domes
TRANSCRIPT
Effect of Membrane Switch Construction on Metal Domes
Test Objective
Evaluate the effect– Square Size– Spacer thickness– Total Thickness over the
dome
has on the tactile responseof a metal dome
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
Trip Force Relative to Number of Actuations
344346348350352354356358360362364366
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
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
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”
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
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
Calibration Hole
450 00
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
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
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
Rebound Force Relative to Offset
50.0100.0150.0200.0250.0300.0350.0
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
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
Travel Relative to Offset
0.01000.01200.01400.01600.01800.02000.02200.02400.02600.02800.0300
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”
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
Switch Test Fixture
•Designed for accurate switch indexing
•Pin index on 1.00” centers
•Index accuracy of 0.003”
•Pin register membrane switch
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 71.89MAX 351.00 118.30 0.02480 75.01MIN 322.10 81.90 0.02360 65.27STD 4.92 4.62 0.00026 1.36
Results
Switch Build-up
.
Switch Layer
DomeAdhesive Spacer
Thickness Over The Dome
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
Trip Force Based on Square Size
Square SizeUnassembled Domes
AVG Trip Force (g)Assembled Domes AVG Trip Force (g) Change in Force (g)
0.390" 336.02 332.19 -3.830.400" 335.65 330.85 -4.810.410" 334.69 330.89 -3.790.420" 336.72 330.93 -5.790.430" 336.10 330.95 -5.150.440" 335.05 330.51 -4.540.450" 335.19 331.07 -4.120.460" 335.14 331.04 -4.11
Thickness Over the Dome = 0.003"
Square SizeUnassembled Domes
AVG Trip Force (g)Assembled Domes AVG Trip Force (g) Change in Force (g)
0.390" 336.02 317.87 -16.090.400" 335.65 321.06 -14.240.410" 334.69 316.22 -16.610.420" 336.72 313.70 -22.940.430" 336.10 316.44 -17.050.440" 335.05 316.99 -17.290.450" 335.19 316.48 -16.920.460" 335.14 315.76 -19.15
Thickness Over the Dome = 0.012"
Rebound Force Based on Square Size
Square SizeUnassembled Domes
AVG Rebound Force (g)Assembled Domes
AVG Rebound Force (g) Change in Force (g)0.390" 94.42 108.37 13.950.400" 93.98 105.89 11.910.410" 94.52 107.49 12.970.420" 94.11 106.86 12.750.430" 93.76 106.21 12.450.440" 94.51 106.47 11.970.450" 93.39 105.75 12.360.460" 93.71 105.56 11.85
Thickness Over the Dome = 0.003"
Square SizeUnassembled Domes
AVG Rebound Force (g)Assembled Domes
AVG Rebound Force (g) Change in Force (g)0.390" 94.42 169.16 75.940.400" 93.98 172.75 79.420.410" 94.52 171.17 79.160.420" 94.11 169.84 75.450.430" 93.76 173.96 78.820.440" 94.51 169.32 73.330.450" 93.39 166.81 74.060.460" 93.71 169.41 77.76
Thickness Over the Dome = 0.012"
Click Ratio Based on Square Size
Square SizeUnassembled Domes AVG Click Ratio (%)
Assembled Domes AVG Click Ratio (%) Change in Ratio (%)
0.390" 72.08 67.03 -4.870.400" 72.17 68.76 -3.230.410" 72.34 66.88 -4.870.420" 71.95 67.80 -4.230.430" 71.46 67.42 -4.670.440" 71.26 66.76 -5.010.450" 72.18 67.95 -4.190.460" 72.62 67.11 -4.92
Thickness Over the Dome = 0.003"
Square SizeUnassembled Domes AVG Click Ratio (%)
Assembled Domes AVG Click Ratio (%) Change in Ratio (%)
0.390" 72.08 46.77 -25.320.400" 72.17 46.21 -25.960.410" 72.34 45.86 -26.480.420" 71.95 45.87 -26.080.430" 71.46 45.01 -26.450.440" 71.26 46.59 -24.670.450" 72.18 47.31 -24.870.460" 72.62 46.35 -26.27
Thickness Over the Dome = 0.012"
Travel Based on Square Size
Square SizeUnassembled Domes
AVG Travel (in)Assembled Domes
AVG Travel (in) Change in Travel (in)0.390" 0.02000 0.02000 -0.000410.400" 0.02420 0.02368 -0.000570.410" 0.02000 0.02000 -0.000510.420" 0.02419 0.02426 -0.000070.430" 0.02418 0.02414 -0.000040.440" 0.02412 0.02375 -0.000370.450" 0.02358 0.02399 0.000410.460" 0.02417 0.02372 -0.00045
Thickness Over the Dome = 0.003"
Square SizeUnassembled Domes
AVG Travel (in)Assembled Domes
AVG Travel (in) Change in Travel (in)0.390" 0.02000 0.02058 -0.003660.400" 0.02420 0.02046 -0.003820.410" 0.02000 0.02038 -0.003780.420" 0.02419 0.02037 -0.003830.430" 0.02418 0.02042 -0.003900.440" 0.02412 0.02070 -0.003390.450" 0.02358 0.02054 -0.003540.460" 0.02417 0.02054 -0.00358
Thickness Over the Dome = 0.012"
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
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
Trip Force Based on Spacer Thickness
Spacer ThicknessUnassembled Domes
AVG Trip Force (g)Assembled Domes AVG Trip Force (g) Change in Force (g)
0.007" 335.44 331.25 -4.190.009" 336.52 333.08 -3.440.011" 335.81 334.17 -1.630.015" 336.11 336.00 -0.10
Thickness Over the Dome = 0.003"
Spacer ThicknessUnassembled Domes
AVG Trip Force (g)Assembled Domes AVG Trip Force (g) Change in Force (g)
0.007" 335.44 307.12 -28.330.009" 336.52 312.33 -24.190.011" 335.81 319.30 -16.510.015" 336.11 327.81 -8.29
Thickness Over the Dome = 0.012"
Rebound Force Based on Spacer Thickness
Spacer ThicknessUnassembled Domes
AVG Rebound Force (g)Assembled Domes
AVG Rebound Force (g) Change in Force (g)0.007" 94.37 107.67 13.300.009" 94.50 109.16 14.650.011" 94.83 108.70 13.870.015" 94.01 110.01 16.00
Thickness Over the Dome = 0.003"
Spacer ThicknessUnassembled Domes
AVG Rebound Force (g)Assembled Domes
AVG Rebound Force (g) Change in Force (g)0.007" 94.37 161.66 67.280.009" 94.50 164.52 70.090.011" 94.83 174.48 79.650.015" 94.01 196.64 102.63
Thickness Over the Dome = 0.012"
Click Ratio Based on Spacer Thickness
Spacer ThicknessUnassembled Domes AVG Click Ratio (%)
Assembled Domes AVG Click Ratio (%) Change in Ratio (%)
0.007" 71.87 66.92 -4.940.009" 71.88 66.69 -5.190.011" 71.72 67.26 -4.460.015" 72.03 67.24 -4.78
Thickness Over the Dome = 0.003"
Spacer ThicknessUnassembled Domes AVG Click Ratio (%)
Assembled Domes AVG Click Ratio (%) Change in Ratio (%)
0.007" 71.87 47.36 -24.510.009" 71.88 47.32 -24.560.011" 71.72 45.35 -26.370.015" 72.03 40.00 -32.02
Thickness Over the Dome = 0.012"
Travel Based on Spacer Thickness
Spacer ThicknessUnassembled Domes
AVG Travel (in)Assembled Domes
AVG Travel (in) Change in Travel (in)0.007" 0.02407 0.02229 -0.001780.009" 0.02442 0.02156 -0.002650.011" 0.02427 0.02166 -0.002610.015" 0.02427 0.02128 -0.00299
Thickness Over the Dome = 0.003"
Spacer ThicknessUnassembled Domes
AVG Travel (in)Assembled Domes
AVG Travel (in) Change in Travel (in)0.007" 0.02407 0.02080 -0.003270.009" 0.02442 0.02050 -0.003710.011" 0.02427 0.02046 -0.003810.015" 0.02427 0.01957 -0.00470
Thickness Over the Dome = 0.012"
Trip force Relative to Spacer and Overlay Thicknesses
300
320
340360
380
400
0.005 0.007 0.009 0.011 0.013 0.015 0.017Spacer Thickness (in)
Trip
For
ce (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
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 0.017Spacer Thickness (in)
Reb
ound
For
ce (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
Click Ratio Relative to Spacer and Overlay Thickness
3540455055606570
0.005 0.007 0.009 0.011 0.013 0.015 0.017Spacer Thickness (in)
Clic
k R
atio
(%)
0.012” Overlay
0.003” Overlay
•Given the trip and rebound forces, click ratio follows the same trend
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
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
• 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
Special Thanks to Name Plates For industry and Automation Alternatives for help with material processing