951 Bergquist, 951 Datasheet - Page 14

• Manufacturer Part Number: 951
• Description: THERMAL PAD TO-220 .009" SP1000
• Manufacturer: Bergquist
• Series: Sil-Pad® 1000r

Specifications of 951

• Usage: TO-220
• Shape: Rectangular
• Outline: 19.05mm x 12.70mm
• Thickness: 0.009" (0.229mm)
• Backing, Carrier: Fiberglass
• Color: Pink
• Thermal Resistivity: 0.35°C/W
• Thermal Conductivity: 1.2 W/m-K
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Adhesive: -
• Other names: 951; BER199

12
Base Metal Layer Design Considerations
t
t
The adjacent graph depicts the CTE of the base material in relationship
to the heat spreading capability of the metal. Although Aluminum and
Copper are the most popular base layers used in Thermal Clad, other
metals and composites have been used in applications where CTE mis-
match is a factor. The adjacent table represents standard and non-stan-
dard base layers.
Coefficient Of Thermal Expansion
And Heat Spreading
Coefficient Of Thermal Expansion
And Solder Joints
Solder joint fatigue can be minimized by selecting the correct base
layer to match component expansion. The major concern with ther-
mal expansion is the stress the solder joint experiences in power (or
thermal) cycling. Solder joints are not mechanically rigid. Stress
induced by heating and cooling may cause the joint to fatigue as it
relieves stress. Large devices, extreme temperature differential, badly
mismatched materials, or lead-free minimum solder thickness may all
place increased cyclic strain on solder joints.
Solder joint fatigue is typically first associated with ceramic based
components and with device termination. The section on “Assembly
Recommendations” (page 18-19) covers these issues in more detail.
Copper
Aluminum 5052
Aluminum 6061
Coefficient Of Thermal Expansion
And Heat Spreading
Coefficient Of Thermal Expansion
And Solder Joints
METAL / ALLOY
CONDUCTIVITY
THERMAL
[W/mK]
400
150
150
THERMAL EXPANSION
COEFFICIENT OF
[ppm/K]
17
25
25
t
t
t
t
Strength, Rigidity And Weight
Electrical Connections To Base Plate
Surface Finish
Costs
DENSITY
[g/cc]
8.9
2.7
2.7
Extra-Long Circuits
Finished circuits up to 25" (635mm) long
MODULUS OF
RIGIDITY
[GPa]
44.1
25.9
26
YIELD STRENGTH
[MPa]
310
215
230