Thermal Management of High Heat Dissipating Electronic Components- LED Module and Metal Diodes
-
Upload
editor-ijritcc -
Category
Documents
-
view
4 -
download
0
description
Transcript of Thermal Management of High Heat Dissipating Electronic Components- LED Module and Metal Diodes
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6075
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Thermal Management of High Heat Dissipating Electronic Components: LED
Module and Metal Diodes
Pal Riya Bipradas Sanchita
ME Student , Dept. Of ETRX, PIIT Engineering College,
Mumbai University, India,
Abstract — Every day, new electronic products such as COB LED lighting products, inverters, metal diodes/rectifier module etc are launched in
the market worldwide. Many of these LED lighting products and high power metal diodes (in the form of rectifier module) come either without
any cooling provision or with low grade cooling provision. Aluminum heat sinks are the most common thermal management hardware solution
in use for majority LED Modules as well as for Metal Diode Rectifier Module. The goal of the work performed and explained in this manuscript
under the title “thermal management of high heat dissipating electronic components: led module and metal diodes” is to first observe and
analyze the extent to which thermal management is achieved by existing Aluminum hardware on a selected LED Module and on Metal Diode
Setups and then developing a new hardware using copper material for the selected LED Module and Metal Diode which will provide an
enhanced thermal management than the existing aluminum hardware solution.
Keywords— Thermal conductivity (k), Thermal Resistance offered by a material (RTH), Source and Sink Junction Resistance (Rthj), Heat
Transfer Rate (Q), Heat flux (q), Aluminum (Al) , Copper (Cu), Heat Sink (H_S).
__________________________________________________*****_________________________________________________
I. INTRODUCTION
1.1 LITERATURE SURVEY ON „COB LED MODULE‟ COOLING TECHNOLOGIES :
In an experiment [1] performed by Dan Pound and Richard W. Bonner, thermal management of single LED was conducted
using solid Aluminum and copper substrate (Fig 1). It had Etched LED circuit at the top and a copper heat pipe (with wire
mesh inserted) at the bottom/backside.
Fig 1: Heat Pipe Embedded In PCB
Angie Fan, Y. Sungtaek Ju , Richard Bonner and Stephen Sharratt [2] conducted an experiment where they developed a new
PCB structure. They have developed PCB (printed circuit board) having PHS (passive heat spreader). This PHS PCB has a
copper chamber and at the base of the LED Chip, a copper thermal pad was integrated. Copper chamber has Cu platted FR-4
type envelop. The complete structure (LEDs + Cu thermal pad + Cu FR-4 envelop +Cu chamber) were fitted to „Al‟ heat sink
hardware using a „Cu‟ lid. This development uses a combination of Al and Cu metals as they are very high heat conduction
materials (Fig 2). Inside the Cu chamber, working fluid undergoes evaporation and condensation processes thus managing the
high performance high heat flux LED‟s thermal issue.
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6076
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Fig 2: PHS PCB
Another experiment (Fig 3) was conducted on multi LED system by Mehmet Kaya [3] , where he used 2 different types of
LED system. One having single LED of 30W and other configuration of 2X15W. He presented the temperature difference of
LED Substrate in both the LED configurations using the integrated fin heat sink design with and without a fan and also with a
heat pipe integrated cooling structure. Results that he obtained are given below in the form of graphical representation.
Fig 3: Left:An Integrated Multi-Fin Heat Sink Design With A Fan and heat pipe. Right: Graph
1.2 LITERATURE SURVEY ON „METAL DIODE‟ COOLING TECHNOLOGIES :
Experiment (Fig 4) conducted by Martin März, illustrates the prototype of a water-cooled technique. This technology
achieves its nominal output power with a coolant temperature of up to 105°C. All power components are thermally coupled
to the heatsink, the power board (FR-4) is double-sided 105μm and copper conducts currents of more than 200A. The
efficiency exceeds 90% over a wide power range. The power density is about 3.5W/cm3.
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6077
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Fig 4: Complete Setup Of Power Converter Having High Power Diodes
Another Experiment (Fig 5) conducted by Martin März on power converters illustrates the use of Copper thermal „vias‟.
Since PCBs offers very bad thermal conduction, these copper sleeves can be inserted inside the PCB exactly lying below the
power semiconductor device mounted at the upper side of PCB. Copper sleeves or vias can be used for semiconductors such
as high current metal diodes and other forms of high power semiconductor devices like SCRs, TRIACS, DIACs, high power
BJTs etc.
Fig 5: Use Of Copper Vias To Cool High Power Diodes
II. DESIGNING OF THE NEW COOLING STRUCTURE USING COPPER METAL STRIP:
1.3 DESIGNING :
New cooling unit (shown in fig 6,C) which has been designed using copper [6], consist of 2 parts. First part is the “corrugated
triangular fins” structure (fig 6,A) and the second part is the “base”(fig 6,B). Number of fins (N), height of fins (H), spacing
between fins (Pf), fin thickness (Ft or (Ta= Tb1=Tb2)) and base plate thickness (b) , base plate length (w) & width (L) will
vary from one application to other. The structure shown in (fig 6,C) is a long running structure. This complete structure can
be folded into any geometrical shape such as one shown in cylindrical form (fig 6,D). Base plate acts as an extra supporting
part which will provide mechanical support as well as it will improve thermal conduction. If number of fins are less then
height is to be increases if heat flux value is high. Even for high heat flux if number of fins are more, then height of fins
should be kept low but spacing between fins must be taken care.
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6078
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Fig 6: (A) shows the corrugated triangular fins structure . (B) Base plate. (C) Complete unit. (D) Square/Rect Structure. (E)
Circular/ Cylindrical Structure
From above fig (6,C), Two conditions/cases are illustrated for heat transfer to take place through corrugated structure. The
T1, T2 &T3 represents highest temperature, mid temperature and low temperature respectively The flow of heat (Q) will
always happen from higher temperature location to lowest temperature location in contact.
Thus Q = f1(T1, T2, strip geometry, material) (1)
The relation between T1 and T2 is in the form of temperature difference (T1-T2) and „x‟ is the separation distance between
T1 & T2.
Q = f2 (T1-T2, strip geometry, material) (2)
Case 1:
If (T1-T2) = 0 (i.e.: when T1 = T2)
Then Q = 0 (means no heat/ thermal transfer rate is being taking place between p1 and p2 points)
Case 2 :
If T1>T2
Then Q>0 (means heat transfer rate increases)
Q α 𝐴.(𝑇1−𝑇2)
𝐿
Q = 𝐾.𝐴.(𝑇1−𝑇2)
𝐿
Q = - 𝐾.𝐴.(𝑇2−𝑇1)
𝐿 (unit: watts)
Qx = - K.A𝑑𝑇
𝑑𝑥 (3)
This is the heat transfer at x direction.
For y and z direction (in 3D representation), Q is given as:
Qy = - K.A𝑑𝑇
𝑑𝑦 (4)
Qz = - K.A𝑑𝑇
𝑑𝑧 (5)
Note: for a very thin copper strip, heat conduction in 3D form can be neglected. Heat flow in any 1 direction can be
considered for simplicity.
Heat Flux (q) is defined as the „rate of flow of heat‟ and Critical heat flux is the „thermal limit of a phenomenon where a
phase change occurs during heating‟.
q = 𝑄
𝐴 (6)
2.1.2 ROLE OF INDIVIDUAL PARAMETERS ON THERMAL CONDUCTIVITY
Thermal Conductivity (K) = 𝑄 .𝐿
𝐴.△𝑇 (7)
1. Temperature difference (△ 𝑇) :
Greater the temperature difference between the two ends of the bar or the strip, greater will be the rate of heat flow.
Q α △ 𝑇 (8)
2. Cross-sectional area (A):
A bar twice as wide conducts twice the amount of heat.
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6079
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Q α A (9)
3. Separation length/ distance (L) :
Rate of heat transfer is always inversely proportional to the length of the bar.
Q α 1
𝐿 (10)
4. Time (t):
Heat flow (Q) directly depends on the amount of time that passes. Twice the time, twice the heat.
2.1.3 THERMAL RESISTANCE (Rth) :
There is an electrical analog with conduction heat transfer [5]. The analog of “Q” or “P” is current “I” , thermal profile “△T”
is voltage difference & thermal resistance “Rth” is Electrical resistance “R”.
Fig 7: Electrical Model and Thermal Model Relation
Ohm‟s Law :
Voltage = Current x Resistance
V= IxR
Fourier‟s Law:
△T= QxRth
Then
Rth = △T/Q
Q = 𝑇1−𝑇2
𝑅𝑡ℎ or
𝑇2−𝑇3
𝑅𝑡ℎ (11)
2.2 TECHNOLOGY USED TO DEVELOP CORRUGATED COOLING UNIT USING COPPER
Technology [4] which has been decided to be used is “Corrugated Triangular Fin Technology”. Where ever it is required
to have high fin density on a restricted surface area at low weight and low manufacturing cost, corrugated fin technology is
given much more importance compared to other technologies such as :
Extruded
Bonded
Die-casting
Skiving
Machining
Forging
Stamping
Folded fins are manufactured by folding continuous strip of copper or aluminum in either a square wave , rect wave , u-
wave or in a triangular wave patterns. After folded fins are manufactured, one can attach a base strip which helps increasing
the heat transfer surface area. Below fig 8 represents the machine used to form triangular corrugated fin structure.
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6080
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Fig 8: Left: Complete View Of The Manually Controlled Corrugated Machine. Right : Triangular Press Region Of The
Machine.
III. EXPERIMENT ON COB LED MODULE : WITH NO COOLING MECHANISM , WITH ALUMINUM
COOLING STRUCTURE & WITH COPPER COOLING STRUCTURE
For this experiment, 6W White Light COB LED has been selected.
Technical Specification of selected 6W White Light COB LED:
1. MODEL: 06-12
2. Input : AC220-240V,50/60Hz
3. Output:DC12-24V max
4. Constant current: 300mA
5. Max Temperature withstand capacity :750C
Fig 9: Left : COB LED Base . Right : Driver Circuit.
In current market, Aluminum heat sink is the only available cooling solution for COB LEDs. In this manuscript, new
hardware cooling structure using copper material is placed. Below TABLE 1 provides the complete specification of existing
cooling “Al” hardware and newly developed “Cu” hardware structures.
TABLE 1: GEOMETRIC DATA OF AVAILABLE “Al” AND DEVELOPED “Cu” HEAT SINK STRUCTURE FOR 6W COB
LED
Sr
No
Parameters Aluminum Heat Sink
Specifications
Copper Heat Sink
Specifications
1 Heat sink material used “Al” “Cu”
2 Type of structure Parallel fins Cylindrical
structure
Corrugated triangular fin
structure
3 Size of the region where this cooling unit is
placed
r = 30mm (i.e. circular region) r = 30mm (i.e. circular region)
4 Weight (LED Module + “Al” structure) 155gm 145gm
5 „Al‟ heat sink attachment/base plate thickness 1 mm 1mm
6 Number of parallel fins 30 10
7 Height limit 35mm 27mm
8 Power Applied
6W 6W
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6081
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Based on the above given specifications of Copper structure, below is the pictorial comparison of COB LED module
without any cooling provision , COB LED module with aluminum structure provided for cooling (this is ready made i.e
available in the current market) and COB LED module with Copper cooling structure.
Fig 10: Left : 6Watts COB LED Module with no cooling unit attached to it.. Middle : Complete LED Module + „Al‟ Heat sink
structure Setup. Right : COB LED module with Copper cooling structure .
Test on chip on board LED was conducted; maximum temperature rise of the board was noted to be 700C without
implementing any cooling provision. This test was conducted for 105minutes. No rise in the board‟s temperature was
noticed above 700C which marked the saturation temperature zone for this LED module without any cooling provided.
When the same test was repeated with aluminum heat sink shown in the above figure 10, only 30C reduction in the LED
board‟s temperature was seen i.e:670C. Temperature test done with new developed copper heat sink, reduced LED board‟s
temperature to 420C i.e 25
0C difference.
Complete experimental data is depicted in TABLE 2,3 & 4 below.
TABLE 2: 6WATTS COB LED TEMPERATURE MEASUREMENT (NO COOLING PROVISION)
Time (min) LED PCB Temp with
no cooling provision
(0C)
(initial ) 0 30
5 37
10 40
15 45
20 48
25 53
30 55
35 57
40 58
45 60
50 60
55 63
60 65
65 65
70 68
75 69
80 70
85 70
90 70
95 70 100 70
105 70
Experiment performed at Room temperature of: 300C
TABLE 3: 6WATTS COB LED TEMPERATURE MEASUREMENT (WITH ALUMINUM COOLING PROVISION)
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6082
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Time
(Min)
Air_Heat-Sink
Junction Temp (0C)
Temp Of Inner
Core Of Heat Sink
(0C)
Light Source PCB
Temp
(0C)
(initial ) 0 30 30 30
5 31 31 36
10 31 36 51
15 34 37 58
20 36 38 60
25 39 40 62
30 39 41 64
35 39 41 65
40 40 42 65
45 40 42 65
50 40 43 65
55 41 44 66
60 43 44 66
65 43 45 66
70 44 46 66
75 45 46 66
80 45 47 66
85 47 49 67
90 47 49 67
95 48 50 67
100 48 50 67
(Final) 105 48 50 67
Experiment performed at Room temperature of: 300C
TABLE 4: 6WATTS COB LED TEMPERATURE MEASUREMENT (WITH COPPER COOLING PROVISION)
Time
(Min)
Air_Heat-Sink
Junction Temp
(0C)
Temp Of Inner
Core Of Heat Sink
(0C)
Light Source PCB
Temp
(0C)
(initial ) 0 30 33 32
5 32 44 35
10 34 44 42
15 33 44 43
20 35 45 42
25 36 41 42
30 33 38 45
35 34 37 43
40 37 42 42
45 36 38 45
50 34 42 46
55 34 43 46
60 36 45 46
65 35 40 44
70 34 44 47
75 36 44 49
80 34 42 42
85 34 39 42
90 33 42 42
95 33 42 42
100 33 42 42
(Final) 105 33 42 42
Experiment performed at Room temperature of: 300C
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6083
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Fig 11: Graph Showing COB LED Module‟s Temperature With No Cooling Provision (Red Line), With Aluminum Heat Sink
(Orange Line) & With Developed Copper Heat Sink (Blue Line).
3.1 CALCULATIONS :
3.1.1 HEAT FLUX (q) of COB –LED :
Fig 12: Showing the Space Consumed By 1 LED
Diameter of LED = 8mm = 0.8cm
Radius = 0.4cm
Area Under 1LED Chip = 3.14 x 0.4 x 0.4 = 0.5cm2
For 6 LEDs, area = 3cm2
Power consumed by LED Module = 6W
Heat flux = power utilized / area = 2W/cm2
3.1.2 “RTH” CALCULATION :
Refer TABLE 3 & 4:
This is to be measured between heat sink’s core (inner/fin base) and heat sink_Air junction Temperature (outer/fin tip).
Formula = Higher Temp −Lower Temperature
Power =
Temp of inner HeatSink Core – HeatSink _Air Junction Temp
Power
TABLE 5 : “RTH” OFFERED BY ALUMINUM AND COPPER STRUCTURES
Sr No Time
(min)
RTH Offered By Aluminum Heat Sink
(0C/W)
RTH Offered By Copper Heat
Sink (0C/W)
1 10 36−31
6 =
5
6 = 0.833
44−34
6 =
10
6 = 1.66
2 35 41−39
6 =
5
6 = 0.333
37−34
6 =
3
6 = 0.5
3 45 42−40
6 =
2
6 = 0.33
38−36
6 =
2
6 = 0.33
4 60 44−43
6 =
1
6 = 0.166
45−36
6 =
9
6 = 1.5
5 85 49−47
6 =
2
6 = 0.333
89−34
6 =
5
6 = 0.888
6 105 50−48
6 =
2
6 = 0.33
42−33
6 =
9
6 = 1.5
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6084
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
3.1.3 HEAT SOURCE AND HEAT_SINK JUNCTION RESISTANCE CALCULATION ( Rthj):
When a heat sink and heat source are in contact with each other, resistance towards the flow of heat path is developed at
their junction. This junction resistance value do not remain constant. It rises to a higher value from low value with
respect to time and then falls again with the flow of time. Rthj has been calculated for certain selected time (min) such as
5, 10, 20, 30, 45, 60, 75, 90, 105 so as to keep illustration simple. This is well illustrated with the below calculations of
Junction Resistance (Rthj) in TABLE 6
Refer TABLE 3 & 4:
Formula = Higher Temp −Lower Temperature
Power
TABLE 6 : “Rthj” OFFERED BY HEAT SOURCE AND HEAT SINK (ALUMINUM & COPPER)
Sr No Time (min) Rthj (Between COB LED board &
Core of Al heat sink junction)
(0C/W)
Rthj (Between COB LED board &
Core of Cu heat sink junction) (0C/W)
1 5 36−31
6 = 0.833
44−35
6 = 1.5
2 10 51−36
6 = 2.5
44−42
6 = 0.33
3 20 60−38
6 = 3.666
45−42
6 = 0.50
4 30 64−41
6 = 3.833
45−38
6 = 1.166
5 45 65−42
6 = 3.833
45−38
6 = 1.166
6 60 64−44
6 = 3.666
46−45
6 = 0.166
7 75 66−46
6 = 3.333
49−44
6 = 0.833
8 90 67−49
6 = 3.00
42−42
6 = 0 = un-measurable
9 105 67−50
6 = 2.833
42−42
6 = 0 = un-measurable
Fig 13: Graphical Representation Of “Rthj” Offered By Heat Source And Heat Sink [Aluminum (Red line) & Copper (blue
line)]
Graph in fig 13 & Table 6 shows that copper heat sink offers less thermal resistance path than aluminum heat sink when
attached with the heat source (i.e COB LED).
3.1.4 COST ESTIMATION :
1. Cost of 1Kg Al = INR 97.795
Cost of 1Kg Cu = INR 351.82
Aluminum used to form this aluminum heat sink shown in fig 10 = 45grams.
Cost of this heat sink = INR 4.4
2. Copper used to form this new heat sink shown in fig 10 = 35grams.
Cost of this heat sink = INR 12.31
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6085
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Conclusion : Cost difference is INR 7.9 . This cost is not very high and COB LED with this developed Cu heat sink is
affordable if we see from the increased lifespan of COB LED Module‟s point of view.
IV. EXPERIMENT ON HIGH VOLTAGE HIGH CURRENT METAL DIODE MODULE : WITH NO COOLING
MECHANISM , WITH ALUMINUM COOLING STRUCTURE & WITH COPPER COOLING STRUCTURE
Below fig 14 (left) represents the block diagram of high current metal diode in the form of metal rectifier module where
aluminum heat sink is used to manage thermal level of metal diodes whereas ( fig 14, right) represents the block diagram of
high current metal diode in the form of metal rectifier module where copper heat sink is used to manage thermal level of
metal diode.
Fig 14:Block Diagram Of Metal Diode In The Form Of A Bridge Rectifier Setup Where Left : Metal Diode With Aluminum
Heat Sink . Right: Metal Diode With Newly Developed Copper Heat Sink/ Cooling Unit
Technical detail of the above mention circuit is given below:
1. Main line voltage = 240V
2. Step down transformer = 12V3A
3. Number of high current metal diodes used = 4
4. Metal diode max. current limit = 12 A -16 A
5. Load : DC Bulb
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6086
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Figure 15: Left: This Figure Shows The Aluminum Heat Sink For Metal Diode Which Is Currently Available In The Market.
Middle: Newly Developed Copper Heat Sink/Cooling Unit For Metal Diode. Right : Metal diode on PCB board. Bottom : Solder
side view of the PCB with Cu Heat Sink
TABLE 7: GEOMETRICAL SPECIFICATION
Sr No Parameters Copper Heat Sink
(Developed)
Aluminum Heat Sink
(Existing)
1 Base height (b) 2 mm 3mm
2 Base length (w) 31mm 35mm
3 Base width (L) 26mm 17mm
4 Number of fins (N) 3 8
5 Fin thickness (Ft) 0.1mm 2mm
6 Fin height (H) 15mm 5mm
7 Fin neck width Not present 10mm
8 Genuine height / vertical height 18mm 26mm
9 Weight 18gm 30gm
10 Setup Power consumption 36W 36W
Experiment was performed at room temperature of 300C where aluminum and copper heat sink were tested for 65minutes.
Aluminum heat sink‟s temperature reached up to 340C which marks the saturated temperature zone for this heat sink.
Temperature reached by metal diode in this experiment was 390C. This proves that heat absorption rate of aluminum heat
sink is slow this resulted main component i.e. metal diode‟s temperature to reach higher value than Al heat sink‟s
temperature.
In the case where copper heat sink was applied, metal diode‟s temperature reached a value of 350C where as copper heat
sink‟s temp was measured to be 370C. This proved that, this designed copper heat sink structure is perfect to cool metal
diode as this structure provides much better heat transfer/ conduction path for metal diode. Copper structure raised its temp
keeping diode‟s temp low. When no cooling provision was implemented in this high voltage high current metal diode then
it reached a saturated temperature zone of 490C. This is well depicted in below TABLE 8.
Table 8: TEMPERATURE READING OF METAL DIODE WITH NO COOLING, WITH ALUMINUM HEAT SINK AND
COPPER HEAT SINK.
Time
(min)
Metal Diode‟s Temp
(0C) with no cooling
provision
Performance with aluminum heat sink Performance with copper heat sink
Metal Diode Temp (0C) Al heat sink‟s Temp (0C) Metal Diode Temp (0C) Cu heat sink‟s Temp (0C)
Initial 0.00 30 30 30 30 30
5 34 30 32 33 30
10 35 30 29 34 34
15 36 29 30 33 34
20 39 33 31 33 34
25 40 33 31 34 35
30 40 37 35 35 36
35 46 37 35 36 35
34 49 38 36 36 35
45 49 39 37 36 35
50 49 37 35 37 35
55 49 38 36 34 37
60 49 39 34 37 36
65 49 39 34 35 37
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6087
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Fig 16: Represents Metal Diode‟s Temperature : Without Cooling Implementation (Red Line) , With Aluminum Heat Sink
(Orange Line) , With Copper Heat Sink (Blue Line)
4.1 CALCULATION :
4.1.1 HEAT FLUX OFFERED BY MEAT DIODE:
1. Diameter of 1 Metal diode = 10mm = 1 cm
2. Radius = 5mm = 0.5cm
3. Area Under 1 Metal diode = 3.14x 0.5x 0.5 = 0.785cm2
4. For 4 Metal diode, area = 3.14cm2
5. Power consumed by Metal diode Module = 36W
6. Heat flux = power utilized / area = 11.46W/cm2
4.1.2 HEAT SOURCE AND HEAT_SINK JUNCTION RESISTANCE CALCULATION ( Rthj):
When a heat sink and heat source are placed one above the other, resistance towards the flow of heat path is developed at
their junction. This junction resistance value do not remain constant. Rthj has been calculated for certain selected time (min)
such as 10, 20, 30, 40, 50 & 60 so as to keep illustration simple. This is well illustrated in below calculations of Junction
Resistance (Rthj) in TABLE 9
Refer TABLE 8:
Formula = Higher Temp −Lower Temperature
Power
TABLE 9: “Rthj” OFFERED BY HEAT SOURCE AND HEAT SINK (ALUMINUM & COPPER)
Sr No Time (min) Rthj (Between COB LED board & Core
of Copper heat sink junction) (0C/W)
Rthj (Between COB LED board &
Core of Al heat sink junction) (0C/W)
1 10 34−34
36 = 0 un-measurable
37−32
36 = 0.138
2 20 34−33
36 = 0.027
40−35
36 = 0.138
3 30 36−35
36 = 0.027
41−36
36 = 0.138
4 40 36−35
6 = 0.027
41.9−37
36 = 0.136
5 50 37−35
36 = 0.05
41.9−37
36 = 0.136
6 60 37−36
36 = 0.027
41.9−37
36 = 0.136
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6088
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
Fig 17: Rthj Graphical Representation.
Graph in fig 17 & Table 9 shows that developed copper heat sink offers less thermal resistance path than aluminum heat sink
when attached with the heat source (i.e metal diode).
4.1.3 COST ESTIMATION :
1. Cost of 1Kg Al = INR 97.795
Cost of 1Kg Cu = INR 351.82
Aluminum used to form this aluminum heat sink shown in fig 15 = 30grams.
Cost of this heat sink = INR 2.338
2. Copper used to form this new heat sink shown in fig 15 = 18grams.
Cost of this heat sink = INR 6.332
Conclusion : Cost difference is INR 3.994 . Again, this cost is not very high and Metal diode with this developed Cu heat
sink is affordable if we see from the increased lifespan of Metal Diode point of view.
V. CONCLUSION
Test on the LED module was carried out for 105 minutes. When the copper heat sink was tested on the COB LED Module,
showed improved thermal management performance over aluminum heat sink. Copper heat sink (cooling unit) was able to
reduce the COB LED module‟s temperature to 420C where as aluminum heat sink was capable of reducing the temperature
up to 670C.When aluminum and copper heat sink was tested on metal diode module for 65minutes, aluminum heat sink
reduced metal diode‟s temperature to 390C where as copper heat sink was capable of reducing this temperature till 35
0C.
This proves that the heat conduction rate of aluminum heat sink is slow compared to copper heat sink. Thus designed copper
heat sink structure is perfect to cool metal diode module as well as COB LED module as this copper structure provides much
better heat transfer/ conduction path.
REFERENCES
[1] Dan Pound, Richard Bonner III, “High Heat Flux Embedded in MCPCB for LED Thermal Management” ,Advanced
Cooling. Technology, 14th
IEEE ITHERM Conference, ppr 267-271, 2014.
[2] Angie Fan, Richard Bonner, Stephen Sharratt and Y. Sungtack Ju, “An Innovative Passive Cooling Method for High
Performance LED”, IEEE 28thSEMI-THERM symposium, 2012.
[3] Mehmet Kaya, “Experiment Study On Active Cooling Systems Used For Thermal Management Of High Power
Multichip Light Emitting Diodes”, Dept. of Mechanical Engineering, The Scientific World Journal, Vol 2014,
ID:563805,7 pages.
[4] Mukesh Kumar , Anil Kumar , Sandeep Kumar,“OPTIMUM DESIGN AND SELECTION OF HEAT SINK”,
International Journal of Application or Innovation in Engineering & Management , Volume 2, Issue 3,ppr 541-549,
March 2013.
[5] S. Lee, “Optimum Design and Selection of Heat Sinks,” Proceedings of 1 lth IEEE Semi-Therm Symposium, pp. 48-54,
1995.
[6] Jafar Mahmoudi * Jussi Vaarno“Copper Heat Sink Design” , Outokumpu Research Center , Finland.
International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169
Volume: 3 Issue: 11 6075 - 6089
______________________________________________________________________________________
6089
IJRITCC | November 2015, Available @ http://www.ijritcc.org
_______________________________________________________________________________________
AUTHOR :
Er. PAL RIYA BIPRADAS SANCHITA received Bachelor Of Engineering in Electronics from PIIT (Pillai Institute Of
Information Technology, Engineering, Media Studies & Research) under Mumbai University. Currently pursuing Master of Engineering. Her
research areas are Power Electronics and Optical Communication. She is the author of (1) „Free Space Light Communication‟. (2) „Negative
Role of Atmosphere On Free Space Light Communication‟. (3) „Heat in Electronic Circuits and Material Selection Criteria for Cooling
Solutions‟, (4) „Measure Of Heat Conduction Through Copper‟, (5) HY510 Grease: Maximum Temperature Support And Its Application In
Cob Led Heat Management , (6) PTC-Cu Heat Sensor & Its Application In Inverter‟s Thermal Testing & (7) Corrugated Technology based
Copper Heat Exchanger for Efficient Thermal Management of Inverter System.