How To Select a Heat Sink
Example A
Find a space saving heat sink to keep a TO-220 device below the
maximum 150°C junction temperature in natural convection. Device
will be screw mounted with an electrically conductive interface.
Example B
Find a heat sink to keep a TO-220 device below the maximum
150 °C junction temperature in forced convection at 400 ft/min.
Device must be electrically insulated and mounted with a labor
saving clip.
Given:
PD = 12 watts
R
θJC
= 2.5°C/W (from semiconductor manufacturer)
TJ max = 140°C (from semiconductor manufacturer)
TA max = 50°C
A Hi-Flow® pad works great with clip mounting and provides the
necessary electrical insulation. Thermal resistance for
Hi-Flow® at low pressure is 1.15°C/W (from page 87).
Using equation 1, solve for R
θSA
R
θSA
= 140 – 50 - (2.5 + 1.15) = 3.85°C/W
12
Many styles are available. If board space is a concern,
533202B02551G (pg 55) meets the requirements.
Air Velocity—Feet Per Minute
400
600
800
HOW TO SELECT A HEAT SINK
Given:
PD = 6 watts
R
θJC
= 3°C/W (from semiconductor manufacturer)
TJ max = 150°C (from semiconductor manufacturer)
TA max = 65°C
A Kondux
TM
pad is a good choice for electrically conductive
applications. Thermal resistance for Kondux
TM
can be determined
from the following graph.
Typical TO-220 Performance
0.60
0.50
(ºC/W)
CS
R
0.40
0.30
0.20
0.10
0.00
0
1
2
3
4
Screw Torque (in-lb)
5
6
80
60
40
20
0
0
2
4
6
Heat Dissipated—Watts
8
10
8
6
4
2
0
Using equation 1, solve for R
θSA
R
θSA
= 150 – 65 - ( 3 + 0.5) = 10.7°C/W
6
The Index by Heat Sink Style on page 8 lists space saving heat sinks.
Several models are in the 10 °C/W range. Choose the one that best
fits the application and verify thermal resistance from graph.
Part number 593202B03500G shows
a 60 °C temperature rise at 6 watts.
0
100
Mounting Surface Temp
Rise Above Ambient—°C
80
60
40
20
0
0
2
4
6
Heat Dissipated—Watts
8
10
200
Air Velocity—Feet Per Minute
400
600
800
1000
10
8
6
4
2
0
53320X
53330X
According to the above graph, an airflow of 400 ft/min results
in a thermal resistance of 3°C/W. This is less than the required
thermal resistance of 3.85°C/W and is therefore acceptable
under these airflow conditions.
If height is a concern, 533702B02552G would meet the
requirements and is only 1.0” tall
Hi-Flow® is a trademark of the Bergquist Company
R
θSA
= 60 = 10.0°C/W
6
Which meets the above requirement in natural convection.
10
AMERICA
EUROPE
www.aavidthermalloy.com
Thermal Resistance From MTG
Surface to Ambient—°C/Watt
USA
Tel: +1 (603) 224-9988 email: info@aavid.com
Italy
Tel: +39 051 764011 email: sales.it@aavid.com
United Kingdom
Tel: +44 1793 401400 email: sales.uk@aavid.com
ASIA
Singapore
Tel: +65 6362 8388 email: sales@aavid.com.sg
Taiwan
Tel: +886(2) 2698-9888 email: sales@aavid.com.tw
Thermal Resistance From MTG
Surface to Ambient—°C/Watt
Mounting Surface Temp
Rise Above Ambient—°C
At 2 in-lb of torque the thermal resistance
is approximately R
θCS
= 0.5°C/W
0
100
200
1000
10
Reading a Thermal Performance Graph
0
100
Mounting Surface Temp
Rise Above Ambient—°C
80
60
40
20
0
0
200
Air Velocity—Feet Per Minute
400
600
800
16
12
8
4
0
1
2
3
4
Heat Dissipated—Watts
5
Thermal Resistance From MTG
Surface to Ambient—°C/Watt
1000
20
Although most fans are normally rated and
compared at their free air delivery at zero
back pressure, this is rarely the case in most
applications. For accuracy, the volume of
output must be derated 60%–80% for
the anticipation of back pressure.
EXAMPLE:
The output air volume
of a fan is given as 80 CFM. The output area
is 6 inches by 6 inches or 36 in
2
or 25 ft
2
.
To find velocity:
GRAPH A
0
100
Mounting Surface Temp
Rise Above Ambient—°C
80
60
40
20
0
0
1
2
3
Heat Dissipated—Watts
4
5
200
GRAPH B
Air Velocity—Feet Per Minute
400
600
800
1000
20
16
12
8
4
0
Thermal Resistance From MTG
Surface to Ambient—°C/Watt
Velocity (LFM) =
Volume (CFM)
area (ft
2
)
Velocity = 80 = 320
0.25
Velocity is 320 LFM, which at 80%,
derates to 256 LFM.
GRAPH A
is used to show heat sink perform-
ance when used in a natural convection envi-
ronment (i.e. without forced air). This graph
starts in the lower left hand corner with the
horizontal axis representing the heat dissipa-
tion (watts) and the vertical left hand axis
representing the rise in heat sink mounting
surface temperature above ambient (°C). By
knowing the power to be dissipated, the
temperature rise of the mounting surface
can be predicted. Thermal resistance in natu-
ral convection is determined by dividing this
temperature rise by the power input (°C/W).
EXAMPLE A:
Aavid Thermalloy part number
579802 is to be used to dissipate 3 watts of
power in natural convection. Because we are
dealing with natural convection, we refer to
graph “A” Knowing that 3 watts are to be dis-
.
sipated, follow the grid line to the curve and
find that at 3 watts there is a temperature
rise of 75°C. To get the thermal resistance,
divide the temperature rise by the power
dissipated, which yields 25°C/W.
GRAPH B
is used to show heat sink per-
formance when used in a forced convec-
tion environment (i.e. with forced air flow
through the heat sink). This graph has its
origin in the top right hand corner with
the horizontal axis representing air velocity
over the heat sink LFM* and the vertical
axis representing the thermal resistance of
the heat sink (°C/W). Air velocity is calculat-
ed by dividing the output volumetric flow
rate of the fan by the cross-sectional area
of the outflow air passage.
Velocity
(LFM)* = Volume
(CFM)**
area (ft
2
)
EXAMPLE B:
For the same application
we add a fan which blows air over the heat
sink at a velocity of 400 LFM.
The addition of a fan indicates the use of
forced convection and therefore we refer
to graph “B” This resistance of 9.50°C/W is
.
then multiplied by the power to be dissi-
pated, 3 watts. This yields a temperature
rise of 28.5°C.
DESIGN ASSISTANCE
Aavid Thermalloy can assist in the design
of heat sinks for both forced and natural
convection applications. Contact us for help
with your next thermal challenge. For more
information, visit our web site at:
www.aavidthermalloy.com
* Linear feet per minute
** Cubic feet per minute
AMERICA
EUROPE
www.aavidthermalloy.com
USA
Tel: +1 (603) 224-9988 email: info@aavid.com
Italy
Tel: +39 051 764011 email: sales.it@aavid.com
United Kingdom
Tel: +44 1793 401400 email: sales.uk@aavid.com
ASIA
Singapore
Tel: +65 6362 8388 email: sales@aavid.com.sg
Taiwan
Tel: +886(2) 2698-9888 email: sales@aavid.com.tw
11
READING A THERMAL PERFORMANCE GRAPH
The performance graphs you will see in this
catalog (see graph 579802) are actually a
composite of two separate graphs which
have been combined to save space. The small
arrows on each curve indicate to which axis
the curve corresponds. Thermal graphs are
published assuming the device to be cooled
is properly mounted and the heat sink is in
its recommended mounting position.
579802
CONVERTING VOLUME
TO VELOCITY
BGA–Solder Anchor
Solder anchor attachment
Aavid's unique Solder anchor attachment method
uses two or four small Solder anchors attached to
the circuit card and a wire spring clip to securely
fasten the heat sink to the device. This method is
rugged, compact and allows for easy removal in
case of rework.
All products include a phase change pad suitable
for most IC package styles to optimize thermal
performance. Models are available with a single
or dual spring clips for additional thermal interface
pressure. Solder anchors are ordered separately.
HEAT SINKS FOR IC PACKAGES
ORDERING INFORMATION
IC Pkg Size (mm)
23 x 23
23 x 23
23 x 23
27 x 27
27 x 27
27 x 27
35 x 35
35 x 35
35 x 35
35 x 35
35 x 35
37.5 x 37.5
37.5 x 37.5
37.5 x 37.5
37.5 x 37.5
37.5 x 37.5
37.5 x 37.5
40 x 40
40 x 40
42 x 40
42.5 x 42.5
42.5 x 42.5
IC Pkg Style
All
All
All
All
All
All
Flip chip
Flip chip
All
All
All
Flip chip
Flip chip
Flip chip
Flip chip
Flip chip
Flip chip
All
All
All
Flip chip
Flip chip
Part Number
374024B60023G
374124B60023G
374224B60023G
374324B60023G
374424B60023G
374524B60023G
10-5634-01G
10-THMA-01G
374624B60024G
374724B60024G
374824B60024G
10-BRD2-01G
10-BRD1-01G
10-BRD1-03G
10-BRD1-04G
10-BRD1-05G
10-BRD1-07G
374924B60024G
375024B60024G
375124B60024G
10-CLS1-01G
10-CLS2-01G
“W” (mm)
23.00
23.00
23.00
27.00
27.00
27.00
31.00
31.00
35.00
35.00
35.00
35.70
37.50
37.50
37.50
37.50
37.50
40.00
40.00
40.00
42.30
42.30
“L” (mm) “H” (mm) “A” (mm)
23.00
23.00
23.00
27.00
27.00
27.00
34.90
34.90
35.00
35.00
35.00
37.30
37.50
37.50
37.50
37.50
37.50
40.00
40.00
40.00
42.30
42.30
10.00
18.00
25.00
10.00
18.00
25.00
23.00
35.00
10.00
18.00
25.00
23.00
23.00
23.00
23.00
23.00
23.00
10.00
18.00
25.00
23.00
35.00
62.30
62.30
62.30
62.30
62.30
62.30
49.70
49.70
49.70
49.70
49.70
49.70
θn
1
40.00
23.40
19.70
30.60
20.30
16.50
11.50
10.70
23.40
15.30
12.00
11.50
10.10
10.10
10.10
10.10
10.10
20.30
12.20
10.30
8.80
8.30
θf
2
11.69
7.39
6.37
9.35
6.46
5.47
4.20
3.95
7.55
5.15
4.27
4.20
3.83
3.83
3.83
3.83
3.83
6.46
4.34
3.83
3.51
3.44
Finish
Black anodize
Black anodize
Black anodize
Black anodize
Black anodize
Black anodize
Black anodize
Black anodize
Black anodize
Black anodize
Black anodize
Clear anodize
Black anodize
Black anodize
Black anodize
Clear anodize
Clear anodize
Black anodize
Black anodize
Black anodize
Black anodize
Black anodize
Fig.
4
1
1
1
1
1
1
2
2
1
1
1
2
2
3
2
3
2
1
1
1
2
2
PCB Fig.
4
A
A
A
A
A
A
C
C
B
B
B
B
B
D
B
D
B
B
B
B
E
E
#Anchors
3
2
2
2
2
2
2
2
2
2
2
2
2
2
4
2
4
2
2
2
2
2
2
SOLDER ANCHOR
Part Number
125700D00000G
125800D00000G
PCB Thickness (mm)
1.60
2.54-2.79
“A” Dim (mm)
3.61
4.70
"A"
0.64
(0.025)
5.08
(0.200)
7.62
(0.300)
7.19
(0.283)
2.49
(0.098)
1. Natural convection thermal resistance based on a 75º C heat sink temperature rise.
2. Force convection thermal resistance based on an entering 1.0 m/s (200LFM) airflow.
3. Solder anchors are sold separately refer to drawing above.
4. Solder anchor mechanical drawings and board mounting drawings see page 13.
12
AMERICA
EUROPE
www.aavidthermalloy.com
USA
Tel: +1 (603) 224-9988 email: info@aavid.com
Italy
Tel: +39 051 764011 email: sales.it@aavid.com
United Kingdom
Tel: +44 1793 401400 email: sales.uk@aavid.com
ASIA
Singapore
Tel: +65 6362 8388 email: sales@aavid.com.sg
Taiwan
Tel: +886(2) 2698-9888 email: sales@aavid.com.tw
BGA–Solder Anchor
Solder anchor heat sinks mechanical drawings
FIGURE 1
FIGURE 2
12.70
(0.500)
"H"
"W"
"L"
54.74
(2.155)
"W"
12.70
(0.500)
"A"
"L"
"H"
FIGURE 3
45.88
"W"
(1.806)
15.00
(0.591)
15.00
(0.591)
"H"
"L"
Board mounting pattern information for solder anchor heat sinks
FIGURE A
35.56
(1.400)
ø 0.97
±
0.03
(0.038
±
0.001)
PLATED THROUGH
HOLES 4 X
Ø
0.97 0.03
(0.038 0.001)
PLATED THROUGH
HOLES 4X
FIGURE B
48.26
(1.900)
26.67
(1.050)
53.34
(2.100)
66.04
(2.600)
33.02
(1.300)
17.78
(0.700)
5.08
(0.200) 2X
24.13
(0.950)
5.08
(0.200) 2x
FIGURE C
FIGURE D
Ø0.97
±
0.03
(0.038
±
0.001)
PLATED THROUGH
HOLES 2X
48.26
(1.900) 2X
58.42
(2.300)
29.21
(1.150)
22.86
(0.900)
5.08
(0.200)2X
33.02
(1.300)
66.04
(2.600) 2X
24.13
(0.950)
FIGURE E
55.88
(2.200)
45.72
(1.800)
Ø 0.97 0.03
0.001)
(0.038
PLATED THROUGH
HOLES 4X
Ø 0.97 0.03
(0.038 0.001)
PLATED THROUGH
HOLES 4X
33.02
(1.300)
27.94
(1.100)
66.04
(2.600)
5.08
(0.200) 4X
5.08
(0.200) 2X
AMERICA
EUROPE
www.aavidthermalloy.com
USA
Tel: +1 (603) 224-9988 email: info@aavid.com
Italy
Tel: +39 051 764011 email: sales.it@aavid.com
United Kingdom
Tel: +44 1793 401400 email: sales.uk@aavid.com
ASIA
Singapore
Tel: +65 6362 8388 email: sales@aavid.com.sg
Taiwan
Tel: +886(2) 2698-9888 email: sales@aavid.com.tw
13
HEAT SINKS FOR IC PACKAGES
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