SJ 20743-1999 Heat Sink Handbook Part 1: Thermal Resistance Curve Collection

This guidance technical document specifies the preferred use of heat sinks under natural cooling and forced air cooling conditions, and gives the thermal resistance characteristic curves of some heat sinks. This guidance technical document is applicable to heat sinks used in electronic devices with heat dissipation (hereinafter referred to as electronic devices). SJ 20743-1999 Heat Sink Manual Part 1: Thermal Resistance Curve Collection SJ20743-1999 Standard Download Decompression Password: www.bzxz.net

Military Standard FL5999 of the Electronic Industry of the People's Republic of China
SJ 207431999
Heatsinkhandbook
Part 1: Thermal resistance curvesPublished on 11-10-1999
Implemented on 12-01-1999
Approved by the Ministry of Information Industry of the People's Republic of China1
Cited Texts
General Requirements
5 Detailed Requirements
Appendix A Heat sink thermal resistance curves (reference) times
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Military Standard of the Electronic Industry of the People's Republic of ChinaHeatsinkhandbook
Part 1: Thermal resistance curves
Heat sink handbook
Part : Thermal resistance curves1.1 Subject content
SJ20743—1999
This guiding technical document specifies the selection method of heat sinks under natural cooling and forced air cooling conditions, and gives the thermal resistance characteristic curves of some heat sinks.
1.2 Scope of application
This guiding technical document is applicable to heat sinks used for electronic components or modules with heat dissipation (hereinafter referred to as electronic devices) in electronic equipment.
2 Reference documents
GB.7423.1-87 General technical conditions for heat sinks of semiconductor devices GB/T12993—-91 Thermal performance evaluation of electronic equipment GJB/Z299A--91 Handbook of reliability prediction of electronic equipment 3 Definitions
3.1 Terms
3. 1. 1 Thermal resistance The resistance encountered by the heat flow dissipated by electronic devices during transmission (through a certain medium). 3.1.2 Heat sinkbzxz.net
Any space that ultimately absorbs heat (such as the atmosphere). 3.1.3 Junction to case thermal resistance (internal thermal resistance) The resistance encountered by the heat dissipated by the electronic device during the process of being transferred from the internal junction to the package shell. 3.1.4 External thermal resistance The resistance encountered by the heat dissipated by the electronic device during the process of being transferred from the package shell to the heat sink including various media. 3.1.5 Thermal resistance of heat sink The resistance encountered when the heat dissipated by the electronic device is transferred from the heat sink to the heat sink 3.1.6 Contact thermal resistance The resistance encountered when the heat flow passes through two mutually contacting media Ministry of Information Industry of the People's Republic of China Issued on November 10, 1999 Implemented from December 1, 1999
3.1.7 Fin heat sink
SJ 20743--1999
An extended surface heat conductor composed of fins of various shapes and the base surface in contact with the heat dissipation surface of the electronic device. 3.1.8 Thermal network
A heat flow path formed by the series, parallel or series-parallel combination of thermal resistances. 3.2 Symbols
TThe temperature of the heat dissipation junction of the electronic device, K; T. The average temperature of the electronic device package shell, K:T, the highest temperature of the heat sink surface, K:T The average temperature of the environment around the heat sink, K:△T: The temperature of the highest temperature point on the heat sink surface and the average temperature of the surrounding environment, K:Rr The total thermal resistance of the system, K/W;
Rrj Junction-shell thermal resistance, KW;
Rt, External thermal resistance (thermal resistance from the electronic device package shell to the surrounding environment), K/W;Rte Radiator contact thermal resistance, (pad thermal resistance) K/W;Re Radiator convection thermal resistance, K/W;
R Radiator radiation thermal resistance, K/W;
Rrr Radiator thermal resistance, K/W:
P. The heat dissipation power of the electronic device, W; The average wind speed flowing through the surface of the heat sink, m/s. 4 General requirements
4.1 Electronic devices with fixed heat dissipation and which cannot meet the heat dissipation requirements by self-heating alone should be installed with a heat sink that is suitable for them.
4.2 The heat dissipation power value of the electronic device should be determined according to the environmental conditions, working properties (pulse power, uniform heating, etc.) and thermal methods.
4.3 The maximum junction temperature and derating factor of the electronic device should be determined according to the requirements of the reliability index and the provisions of GJB/Z299A according to the boundary limit value of the environmental conditions. 4.4 The heat sink thermal resistance value provided in the heat sink thermal resistance curve in Appendix A (reference) should be used to select the heat sensor. 4.5 The contact thermal resistance between the heat sink and the mounting surface of the electronic device should be reduced. 4.6 The placement of the heat sink should be conducive to the transmission of heat flow. 4.7 The physical properties and chemical composition of the heat sink material should comply with the provisions of relevant national standards. 4.8 The surface of the heat sink should be protected, and the requirements of environmental protection and heat transfer should be taken into account. 5 Detailed requirements
5.1 The heat sink product should comply with the provisions of GB7423.1. 5.2 The steady-state equivalent thermal network of the heat transfer system composed of electronic devices and heat sinks during its operation is shown in Figure 1.
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Note: RTp has a relatively large relative value and can be ignored.
SJ20743-1999
Figure 1 Equivalent thermal network diagram
The thermal resistance values ​​in the equivalent thermal network are calculated according to the following formula: Rr Ru+Rte+Rrr
5.3 According to the test method specified in GB/T12993, the values ​​of Pc, T, T, T, and other parameters in the formula should be tested to determine the thermal resistance value of the radiator. The thermal resistance curve of the radiator under natural cooling and forced air cooling conditions is shown in Appendix A (reference).
5.4 The main methods to reduce the contact thermal resistance (Rc) between the electronic device and the contact surface of the radiator include: a. Under the condition that the structural strength permits, choose a softer metal material (usually L2~L6) to make the radiator: b. Improve the surface roughness requirements of the contact surface; c. Lay a cushion layer with good thermal conductivity between the two contact surfaces, such as thermal conductive paste; when there is a requirement for electrical insulation! A conductive cushion layer with electrical insulation should be selected: such as thermal conductive rubber, thermal conductive diaphragm, etc.: d. The two contact surfaces should have a stable fastening pressure, such as fastening screws, taking anti-loosening measures, etc. 5.5 The surface treatment of the radiator can be carried out according to the requirements of Table 1. The color of the radiator surface is generally black, 3
Radiator material
Aluminum and aluminum alloy
Emulsification sensitive
SJ 20743-1999
Coating
Ink anode fluorination, insulation thermal conductive coating, etc. Black chemical coating, insulation thermal conductive coating, plating pot, nickel, etc. are not coated and baked
5.6 The preferred order of the cross-sectional shape of the radiator fins is trapezoidal toothed ribs, trapezoidal ribs, triangular ribs, etc., as shown in the figure. Tooth-shaped lung
Trapezoidal rib
Triangular rib
Figure 2 Cross-sectional shape of fin
5.7 The placement of the radiator should make the longitudinal direction of the fin consistent with the airflow direction. 4
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A1 Model compilation
SJ20743—1999
Appendix A
Heat resistance curve collection of heat sink
(reference)
The heat sink product model in this appendix is ​​in accordance with GB7423.1. A2 Curve drawing method
The thermal resistance curve in this appendix plots the thermal resistance characteristic curves of natural cooling and forced air cooling in the graph. In the graph, V-RT coordinates indicate that the curve corresponds to forced air cooling; P△T coordinates indicate that the curve corresponds to natural cooling. The two curves have no corresponding relationship. If there is no wind speed (V) coordinate in the graph, it means that the curve only gives the thermal resistance characteristics of natural cooling
A3 Radiator placement
The thermal resistance curves listed in this appendix are measured and drawn according to the following conditions. When it is naturally cooled, the radiator is supported by a special bracket, and its fins are vertical in the longitudinal direction. The vertical distance between the lower end of the radiator and the bottom of the test box is 120mml: When it is forced air cooling, the radiator base plate is placed horizontally, and its fins are parallel to the airflow direction in the longitudinal direction. It is placed in the middle of the central section of the wind tunnel test section with a special bracket. A4 Radiator Material
SRX series is aluminum profile radiator, material is L6, LD31; SRS series is stamping radiator, material is A3. A5 Radiator Thermal Resistance Curve
Some radiators and their thermal resistance curves are shown in Figures A1 to A33 respectively. -5-
SJ 20743-1999
SRXHDQ
SRXi1DQ
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3.0V(m/s)
15 pe (w)
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SRX12DQ
SRX120QL=130m
3.0 (m/s)
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SRX13DQ
SRx13Q
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3.0 V (mls)
30 p(w)
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SRX14DQ
SRXL4DQ
L-80mm
3.0 v(m/s2
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SRX1SDQ
SRX15DQ
L -120 mm
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3.0 V(m/s)
J5pe(w)
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