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Micro-Coil Springs
MSC Series
Interconnect for CCGA
 
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    Size Comparison on Penny On CGA  •   Fillet  •   Top SnPb Plated
3D Model
Ni Gold Plated
3D Model 
 
Pad
Pitch
Spring
Diameter

O.D.
Spring Length
Free Load
Wire
Diameter
Spring
Constant
PCB Land Pad
Diameter Minimum
Paste
Stencil

Thickness
Note 1.
Part Number DWG
Number
Plating
1.0mm Ø0.40mm
0.016"
1.0mm
0.040"
Ø63.5µm
0.0025"
0.4627 N/mm
2.6423 lbs/Inch
Ø0.508mm
0.020"
125µm
5 Mil
MCS172P16x40 171640 Sn60Pb40
Tin-Lead
100 µ-inch
1.0mm Ø0.40mm
0.016"
1.0mm
0.040"
Ø63.5µm
0.0025"
0.4627 N/mm
2.6423 lbs/Inch
Ø0.508mm
0.020"
125µm
5 Mil
MCS172G16x40 191640 NiAu
Gold 10 µ-inch
Nickel 30~60µ-inch
1.0mm Ø0.51mm
0.020"
1.27mm
0.050"
Ø86µm
0.0034"
0.6268 N/mm
3.5792 lbs/Inch
Ø0.635mm
0.025"
125~150µm
5~6 Mil
MCS172P20x50 172050 Sn60Pb40
Tin-Lead
100 µ-inch
1.0mm Ø0.51mm
0.020"
1.27mm
0.050"
Ø86µm
0.0034"
0.6268 N/mm
3.5792 lbs/Inch
Ø0.635mm
0.025"
125~150µm
5~6 Mil
MCS172G20x50 192050 NiAu
Gold 10 µ-inch
Nickel 30~60µ-inch
Note 1: Stencil thickness may vary based on many factors such as solder paste powder size, flux and pad diameter. The fillet (after reflow) should cover the closed double end-coils without touching the active rings. Designers should use their own experience during process development.
Ø0.51mm x 1.27mm Micro-Coil Springs (Ø20 x 50mils) attached to CCGA1152 35x35mm Pitch 1.0mm
Bottom Detail Perspective Top
        
 
Description of Micro-coil Springs (MCS Series)
 

Micro-coil springs are a novel interconnect for CCGA (Ceramic Column Grid Array) IC packages for harsh environments. In tests using daisy chain test vehicles, Micro-coil springs absorbed extreme shock of up to 50,000g before failing. Commercial applications include aerospace, avionics, military, down-hole oilfield drilling and automotive electronics. Test results presented at IEEE CPMT 2012.

 

NASA granted an exclusive license to TopLine under U.S. Patent Application Serial No. 13/800,692 entitled Interconnect Device and Assemblies Made Therewith. July 2013 NASA technology transfer. 2014 NASA Contest Winner Tech Briefs

 

Daisy chain test vehicles described in Micro-Coil Spring NASA document 2011. Characterization provided by Auburn University. Thermal performance described in 2009 Internship Report.

 

Micro-coil springs are fabricated from beryllium copper C17200 (Alloy 25) per ASTM B 197. The coils are post-plated with electro-deposited Sn60/Pb40, 100 micro-inches minimum thickness. Micro-coil springs may also be used in place of solder balls on plastic PBGA packages. After reflow at normal tin-lead temperature profiles, Sn63/Pb37 solder paste forms a fillet around the double coil ends of the spring.
 

Engineers at NASA's Marshall Space Flight Center developed this novel interconnection structure for integrated circuit packages. This innovation replaces traditional CCGA solder columns with the potential to extend life under harsh environments, extreme thermal stress, vibration and shock. The Micro-coil Spring technology provides flexibility in three dimensions between the ceramic (or plastic) package and the PCB board. This technology offers a distinct improvement over cast Pb90/Sn10 solder columns or copper-ribbon-wrapped Pb80/Sn20 solder columns, which have limited flexibility under shear stress. NASA's technology offers a novel alternative, providing better flexibility in high temperature and harsh environments.

 
 
Benefits:
    Improved Reliability:
  • Reduced electrical failures due to connection breaks caused by thermal stress.
  • >10,000 thermal cycles without failures.
    Robust, Rugged and Tough:
  • Resilient spring interconnect returns to home position.
  • High tolerance for temperature extremes, thermal cycling and vibration.
  • Improved three-dimensional flexibility versus traditional solder columns.
  • Absorbs CTE (Coefficient of Thermal Expansion) mismatch between ceramic substrates and FR4/Polyimide PC boards.
    Smaller Geometries:
  • Standard I/O pitch 1.0mm to 1.27mm
  • Reduced I/O pitch 0.5mm, 0.65mm and 0.8mm under development
    Cost-Down:
  • More reliable performance means fewer failures.
  • Increased mean-time between failures.
    Export:
  • EAR99 classification.
  • Not listed with a specific Export Control Classification Number (ECCN) on the Commerce Control List (CCL).
 
 
 
Life Test Micro-Coil Compared to BGA
Weibull Analysis
Fig. 1A   Fig. 1B
 
Weibull#1
Ceramic CBGA compared to Micro-Coil Spring

CBGA Pb90/Sn10 ball experienced onset of failure after 300 cycles with last channels failing after 600 thermal-cycles -55°C to +125°C. Micro-Coil Springs mounted onto ceramic substrates of similar size survived on average 5000 thermal-cycles.
  Weibull#2
Plastic PBGA compared to Micro-Coil Spring

Plastic (Organic) PBGA Sn63/Pb37 ball experienced onset of failure after 2000 cycles with last channels failing after 4000 thermal-cycles -55°C to +125°C. Micro-Coil Springs mounted onto plastic substrates of similar size survived on average 20000 thermal-cycles.
 
 
Micro-Coil Spring Models
Shock Simulation
Fig. 2   Fig. 3
 
MCS FEM (FINITE ELEMENT ANALYSIS)
MCS deflection time history after shock,

40,000g simulation with deflection milli-second time history.
Other g-levels are similar in contour with different magnitudes.
  Cut Away View
Double End Coil

 
 
 
Micro-Coil Spring Models
Stress Contours During Compression and Maximum Deflection
Fig. 4   Fig. 5
 
While Compressed
Stress Contours

Stress concentrations occur only during the end of the compression cycle. Failure is likely to occur in the coil windings rather than at the solder fillet.
  Maximum Deflection
Stress Contours

Shear stresses in the coil are the highest in magnitude. Stress concentrations occur only for the two shear stress contours. Failure is likely to occur in the coil windings rather than at the solder fillet.
 
 
PC Board Deflection and Failure Mode
Fig. 6   Fig. 7
 
1500g Drop Test
Un-deflected, Negative & Positive Deflection
Deflection during standard 1500g test
in accordance with JEDEC standards
  Comparison of Extreme Shock Repetition
Micro-Coil Springs 30,000g to 50,000g
to induce Failure Mode
 
 
Comparison Failure Mode
After Application of Extreme Shock
Micro-coil Springs (MCS172P20x50) versus Pb90/Sn10 Wire Columns
Shock Level Micro Coil Spring Pb90/Sn10 Wire
30,000g 30-times before failure 7-Times before failure
40,000g 16-times before failure 5-Times before failure
50,000g 8-times before failure 4-Times before failure
 
 
View of Failure Mode
Fig. 8   Fig. 9
 
Cross Section View
Failed Micro-coil spring with a crack shown perpendicular to ceramic substrate (above double-end of the coil at top) after thermal cycling.
  Side View MCS172P20x50
Failure Micro-coil springs break in wire after thermal cycling.
 
 
 
Fig. 10
Reflow Temperature Profile
  Fig. 11
NASA Technology Transfer
 
Vapor Phase Reflow.
Temperature profile used by NASA
to attach Micro-coil springs to ceramic CCGA
using Sn63/Pb37 solder paste.
  NASA Announces Technology Transfer
NASA grants an exclusive license to TopLine.
Read More.
 
 
 
Fig. 12
Gold Plated Micro-Coil Spring
Side View
  Fig. 13
Gold Plated Micro-Coil Spring
Top View
 
RoHS Version.
Attached to ceramic substrate with SAC305 solder paste.
Stencil 6mil (150um) thick with Ø26mil (660um) aperture.
  0.5mm x 1.27mm coils.
Centered on Ø 0.8mm Ni-Au pad.
 
 
 
Assembly Guidelines
PCB Pads and Solder Paste Stencil
I/O Pitch Spring
Diameter
Spring
Length
Recommended
Solder Mask
Type
Pad
Diameter
Minimum
Pad
Diameter
Maximum
Paste
Stencil
Aperture
Paste
Stencil
Thickness
Coil Part Number
1.0 to 1.27mm Ø 0.020"
0.508mm
0.050"
1.27mm
NSMD Ø 0.025"
0.635mm
Ø 0.034"
0.86mm
1:1 Size
of Pad
5~6 mils
0.125~0.150mm
MCS172P20x50
Note 1. Solder Mask Type Definition: Non-solder Mask Defined (NSMD) pad recommended. Solder Mask Defined (SMD) Pad permissible under alternate conditions.
Note 2. Recommended to use vapor pahase reflow oven.
Note 3. Flux is allowed on CCGA Substrate
Note 4. Kester EP256 Sn63/Pb37 solder paste with Type 3 powder mesh and ROL0 no-clean flux used in trial runs. Other solder paste is permitted.
Note 5. Kester EM907 SAC305 - Sn96.5/Ag3.0/Cu0.5 lead free solder paste with Type 3 powder mesh and ROL0 no-clean flux used in trial runs.
Other solder paste is permitted.
Note 6. Shearing (shaving) or trimming of Micro-coil springs is not required after attachment to the CCGA substrate, as is typically required for traditional solder colummns.
 
 
 
Electrical Parameters
(Preliminary)
Spring
Diameter
Spring
Length
Inductance
(500 MHz~10 GHZ)
Capacitance DC
Resistance
Coil Part Number
Ø 0.020"
0.508mm
0.050"
1.27mm
≈ 4.7 nH To be
determined
≈ 0.03 Ω MCS172P20x50
 
 
 
Micro-Coil Spring Part Number System
 
    MCS         172         P         20         X         50         Option    
Column Type Alloy Plating Ø Diameter
Mils
Packaging Length
Mils
  Option
MCS = Micro Coil Spring 172
BeCu
C17200
Alloy 25
P = Sn60/Pb40
G = Ni/Au

O.D. Diameter
06 = Ø0.15mm
08 = Ø0.20mm
10 = Ø0.25mm
12 = Ø0.30mm
14 = Ø0.35mm
16 = Ø0.40mm
18 = Ø0.45mm
20 = Ø0.50mm
35 = Ø0.89mm
X = Bulk Free Load Length
15 = 0.38mm
20 = 0.50mm
25 = 0.65mm
30 = 0.76mm
33 = 0.85mm
35 = 0.90mm
40 = 1.00mm
45 = 1.15mm
50 = 1.27mm
87 = 2.20mm
  TBA
 
 
Micro-Coil Spring Drawing Number
 
    17         20         50    
MCS Plating Ø Diameter
Mils
Length
Mils
MCS Micro Coil Spring
17 = Sn60/Pb40

19 = Ni/Au
Ni 30~60 micro-inches (0.76~1.5µm)
Au 10 micro-inches (0.25µm)
O.D. Diameter • Typical Pitch
06 = Ø0.15mm  • P~0.4mm
08 = Ø0.20mm  • P~0.5mm
10 = Ø0.25mm  • P~0.65mm
12 = Ø0.30mm  • P~0.8mm
14 = Ø0.35mm  • P~0.8mm
16 = Ø0.40mm  • P~1.0mm
18 = Ø0.45mm  • P~1.0mm
20 = Ø0.50mm  • P~1.0mm
35 = Ø0.89mm  • P>1.5mm
Micro Coil Spring
15 = 0.38mm
20 = 0.50mm
25 = 0.65mm
30 = 0.76mm
35 = 0.90mm
40 = 1.00mm
45 = 1.15mm
50 = 1.27mm
87 = 2.20mm
 
 
Properties of Performance
 
Alloy Solidus Liquidus Density
gm/cc
Modulus of
Elasticity
Electrical
Conductivity
% of IACS
Thermal
Conductivity
CTE
Coefficient
Thermal
Expansion
Tensile
Stength
Beryllium Copper
Hard Temper TD05
C17200
Alloy 25
Cu 98%
Be 1.8%
Co+Ni 0.2%
-- 865°C 8.36 131 GPa 22~28 105 W/m-K 17.5ppm/°C 1100 MPa
 
Pb90/Sn10
Solder
275°C 302°C 10.5 490 GPa 8.2 36 W/m-K 27.9ppm /°C 30 MPa
 
Pb80/Sn20
Solder
183°C 280°C 10.0 ~500 GPa 8.7 37 W/m-K 26.5ppm /°C 33 MPa
Ambient temperature is ~25 °C.
Coefficient of thermal expansion is defined as the fractional increase in the length per unit rise in temperature.
CTE units may be expressed in units of: µm/m/°C or ppm/°C or µ-inch/in/°C.
Metric Units of GPa are gigapascals (109Pa)   •   Metric Units of MPa are megapascals (106Pa)
Data is for information only and is not guaranteed for accuracy.
 
 
 
ECCN: EAR99 Export Administration Regulations (EAR)
HS Code: 8542.90.0000 ELECTRONIC INTEGRATED CIRCUITS AND MICROASSEMBLY PARTS
ITAR: Micro-coil springs and dummy daisy chain CCGA are not restricted.
 
 
 
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