New GeneraEon of Probe Alloys

New Genera)on of Probe Alloys Dr. Edward F Smith, III, Jason Kumnick, Bruce Quimby, Art Klein Deringer-­‐Ney, Inc. Overview Increases in overall wafer size coupled with ever decreasing
feature size places tremendous pressure on optimizing the
materials used for semiconductor test probes.
This is especially true as the test environment pushes to smaller
diameter probes required by today’s micro and nano revolution.
It is well known that material characteristics such as electrical
conductivity and hardness play a key role in probe performance.
However, other material properties (temper, formability, etc.) may
also influence performance, reliability and life cycle cost of the
probes.
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Presenta)on Outline •  Semiconductor History –  Impact of more powerful IC’s –  Product evolu)on demanding smaller probes •  Relevant Material Proper)es –  Spring Constant –  Hardness –  Conduc)vity -­‐ CCC Performance –  Formability •  Important Factors Affec)ng Life)me –  Star)ng temper & Forming –  Prolonged thermal exposure 3
Quick Review of IC History 4
IC Evolu)on •  Overall wafer size geTng larger –  More dies per wafer –  More complex tes)ng protocol •  Feature size geTng smaller –  Maintain func)on -­‐ smaller components –  Increased func)on -­‐ more power, higher test currents –  Higher test temperatures 5
Power Consequences •  Transistor count increases with Moore’s law Doubles approximately every 2 years •  Higher transistor count means more power •  More power means test probes must carry more current •  More current means probes run hoXer 6
Test Probes 7
Evolu)on of Ver)cal Probe Size 1978 – 0.178 mm (.007”)
1985 – 0.127 mm (.005”)
2000 – 0.089 mm (.0035”)
2009 – 0.064 mm (.0025”)
2013 – 0.038 mm (.0015”)
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Single Probe in Card FORCE (Touchdown)
Center Buckles
And applies force
Single Probe
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Fully Populated Card Array
can approach
10,000 pins
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Size Consequences •  Chip Real Estate is at a premium •  Higher density of smaller features •  Result-­‐ pad sizes must shrink •  Since probe )ps must contact the pads •  Probe diameter/ )ps must also get smaller •  Smaller diameter means probes run hoXer 11
Noble Metal Alloy Op)ons 12
Alloy Proper)es (Nominal) Properties
HT Conductivity
Paliney H3C
Paliney 7
(Pd-Ag-Cu-Pt-Au)
(Pd-Ag-Cu)
Paliney C
(Pd-Ag-Cu)
5.5
14.5
16.5
Annealed
UTS
Hardness
120 ksi
230Hv
170 ksi
260Hv
125 ksi
260Hv
Heat Treated
UTS
Hardness
180 ksi
380Hv
250 ksi
475Hv
190 ksi
385Hv
Benefits
High nobility,
Low CR
High Conductivity
High Hardness,
Low CR
High Conductivity,
Low CR
(%IACS)
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Material Proper)es •  Spring Constant – Affects Gram Force –  Controlled by Elas1c Modulus and Geometry 14
Material Proper)es •  Hardness – Affects wear / point life 15
Material proper)es -­‐Formability Measurement Techniques –  Repeated 90° bends •  # of Bends •  Modified protocol –  Improved reproducibility –  Roll to Ribbon 10
•  Rated on a scale 1-­‐10 5
1 =Open Cracks 10 =No Visible Strain Lines 1
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Results of Formability Tests 17
Material Proper)es •  Electrical Conduc)vity %IACS Conductivity
18.0%
16.0%
14.0%
12.0%
10.0%
8.0%
6.0%
4.0%
2.0%
0.0%
Pal 7
H3C
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Pal C
CCC Tes)ng Current Carrying Capacity (CCC) Methodology Load probe to recommended overdrive Measure gram force Apply current to the probe – to reach steady state Turn current off Allow the probe to cool Measure gram force of Probe at the end of each current cycle Incrementally increase current Repeat process un)l gram force is less than 80% of ini)al gram force CCC defined as the current level where probe force is 20% lower than the ini)al force 19
CCC test cell Micrometer
load cell
Power Supply
Multimeter
Wafer
Hot Chuck
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Effect of Electrical Conduc)vity 15% IACS
5.5% IACS
0.102mm (.004”) diameter probes
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Alloy CCC Data Probe Size
4.0 mil
3.5 mil
3.0 mil
2.5 mil
Paliney 7
Paliney H3C
(14.5% IACS)
(16.5% IACS)
1.10 A
1.05A
.90A
1.75A
1.35A
1.10A
0.95A
1.75A
(5.5% IACS)
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Paliney C 0.95A
Alloy CCC Data 20% CCC Results 2 1.5 Pal 7 1 H3C 0.5 Pal C 0 0 2 4 6 8 10 12 Wire Cross Sec)onal Area (sq.in. x 10-­‐6) 23
14 Factors Affec)ng Probe Life)me •  Ini)al Material Proper)es are altered by: –  Probe Forming –  Prolonged Thermal Exposure •  Re-­‐evaluate proper)es in process 24
Factors Affec)ng Probe Life)me •  Star)ng temper and Affect of cold work (forming) Conduc)vity 20.00% 15.00% Ann 10.00% HT Formed (50% CW) 5.00% 0.00% Pal 7 H3C 25
Pal C Factors Affec)ng Probe Life)me •  Prolonged thermal exposure –  Alloy Soaening -­‐ 200°C Hardness, HK100 500 450 Pal 7 400 Pal H3C 350 Pal C 200°C 250°C 300 0 200 400 600 800 Time, hrs 26
1000 1200 Factors Affec)ng Probe Life)me •  Prolonged thermal exposure Resistance, mΩ
Contact Resistance 125°C Air Oxidation
16
14
12
10
8
6
4
2
0
Pal C
H3C
0
1000
2000
Time, hours
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3000
4000
Conclusions •  Current Market demands op)mized materials –  Electrical Conduc1vity and Hardness play key role in determining material performance. •  Reliability and life cycle cost also determined by: –  Star1ng Temper –  Tes1ng Environment –  Probe Forming 28
Conclusions •  Notable DNI Materials for Probes –  Paliney 7 •  Industry Benchmark – Low Conduc1vity –  Paliney H3C •  High Hardness and Conduc1vity, Lower Formability –  Paliney C •  Hardness of Paliney 7 •  Higher conduc1vity than H3C. •  Increased Formability 29
Acknowledgements The authors would like thank Joey Wu of MPI for performing and sharing the ccc tests and the spring rate measurements We would also like to thank ScoX Marquis and Dave Birdsall from our lab for all their assistance during the development and tes)ng of these new alloys Ques)ons ? 31
Thank you! Dr. Edward F. Smith, III Deringer Ney, Inc.