1、 JEDEC STANDARD Integrated Circuits Thermal Test Method Environmental Conditions - Natural Convection (Still Air) JESD51-2A (Revision of JESD51-2, December 1995) JANUARY 2008 JEDEC SOLID STATE TECHNOLOGY ASSOCIATION NOTICE JEDEC standards and publications contain material that has been prepared, rev
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3、hangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for use by those other than JEDEC members, whether the standard is to be used either domestically or internationally. JEDEC standards and publications are adopted wi
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7、ll (703) 907-7559 or www.jedec.org Published by JEDEC Solid State Technology Association 2007 2500 Wilson Boulevard Arlington, VA 22201-3834 This document may be downloaded free of charge; however JEDEC retains the copyright on this material. By downloading this file the individual agrees not to cha
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10、 JEDEC Standard No. 51-2A -i- INTEGRATED CIRCUITS THERMAL TEST METHOD ENVIRONMENTAL CONDITIONS - NATURAL CONVECTION (STILL AIR) Foreword This document is in the JESD51 series of specifications that specify the methods to determine and report the thermal performance of integrated circuit packages. Th
11、e specification was formulated under the cognizance of the JC-15.1 Committee on Thermal Characterization Techniques for Electronic Packages and Interconnects. Introduction The purpose of this document is to outline the environmental conditions necessary to ensure accuracy and repeatability for a sta
12、ndard junction-to-ambient (JA) thermal resistance measurement in natural convection. Without the standardized control of the environment, the test results from different vendors or from different packages will not be consistent and cannot be used to judge relative performance. The intent of JAmeasur
13、ements is solely for a thermal performance comparison of one package to another in a standardized environment. This methodology is not meant to and will not predict the performance of a package in an application-specific environment. NOTE: “Still air” (in the title) signifies natural convection in a
14、n enclosure as opposed to a natural convection measurement made in a wind tunnel with the blower off. JEDEC Standard No. 51-2A -ii- JEDEC Standard No. 51-2A Page 1 INTEGRATED CIRCUITS THERMAL TEST METHOD ENVIRONMENTAL CONDITIONS - NATURAL CONVECTION (STILL AIR) (From JEDEC Board Ballot JCB-07-111, f
15、ormulated under the cognizance of the JC-15.1 Committee on Thermal Characterization Techniques for Electronic Packages and Interconnects. 1 Scope The environmental conditions described in this document will apply only to natural convection, JA, measurements for packages mounted on standard test boar
16、ds. The board will be placed in a horizontal (package up) position in an enclosure that prevents extraneous air currents and allows only natural convection generated by the package under test. 2 Normative reference The following normative documents contain provisions that, through reference in this
17、text, constitute provisions of this standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the norma
18、tive documents indicated below. For undated references, the latest edition of the normative document referred to applies. 1 JESD51, Methodology for the Thermal Measurement of Component Packages (Single Semiconductor Devices). This is the overview document for this series of specifications. 2 JESD51-
19、1, Integrated Circuit Thermal Measurement Method - Electrical Test Method 3 JESD51-3, Low Effective Thermal Conductivity Test Board for Leaded Surface Mount Packages 4 JESD51-4, Thermal Test Chip Guideline (Wire Bond Type Chip) 5 JESD51-5, Extension of Thermal Test Board Standards for Packages with
20、Direct Thermal Attachment Mechanisms 6 JESD51-6, Integrated Circuit Thermal Test Method Environmental Conditions Forced Convection (Moving Air) 7 JESD51-7, High Effective Thermal Conductivity Test Board for Leaded Surface Mount Packages 8 JESD51-8, Integrated Circuit Thermal Test Method Environmenta
21、l Conditions Junction-to-Board 9 JESD51-9, Test Boards for Area Array Surface Mount Package Thermal Measurements 10 JESD51-10, Test Boards for Through-Hole Perimeter Leaded Package Thermal Measurements 11 JESD51-11, Test Boards for Through-Hole Area Array Leaded Package Thermal Measurements 12 JESD5
22、1-12, Guidelines for Reporting and Using Electronic Package Thermal Information 13 JESD30D, Descriptive Designation System for Semiconductor-device Packages JEDEC Standard No. 51-2A Page 2 3 Terms and definitions For the purposes of this standard, the terms and definitions given in JESD51-1, Integra
23、ted Circuit Thermal Measurement Method - Electrical Test Method and the following apply: TA- Ambient air temperature. TA0- Initial ambient air temperature before heating power is applied. TAss- Final ambient air temperature after heating power is applied and steady-state has been reached. TT0- Initi
24、al package (top surface) temperature before heating power is applied. TTss- Final package (top surface) temperature after heating power is applied and steady-state has been reached. JB- Thermal characterization parameter to report the difference between junction temperature and the temperature of th
25、e board measured at the top surface of the board as described in section 7. This measurement must be done on boards with two internal planes such as specified in JESD51-7 or JESD51-9. JT- The thermal characterization parameter to report the difference between junction temperature and the temperature
26、 at the top center of the outside surface of the component package, divided by the power applied to the component. When Greek letters are not available, JT is written Psi-JT. 4 Environmental conditions for natural convection measurements 4.1 Test enclosure assembly The enclosure shall be a box with
27、a nominal inside dimension of 305 mm x 305 mm x 305 mm as shown in Figures 1 and 2. This is approximately 1 foot x 1 foot x 1 foot in keeping with previous specification. All seams should be thoroughly sealed to ensure no airflow through the enclosure. A list of potential construction materials is d
28、etailed in 4.6. The box material shall be a low conductivity material (less than 0.5 W/m K). The box should sit on a table or shelf constructed of low conductivity material. NOTE For high power devices, dissipating 3 watts, increasing the size of the box should be considered if the ambient temperatu
29、re rise above the initial ambient temperature is 10% or more of the rise in junction temperature during the test (TJ). Any dimensional changes in the box size must be reported in the data and labeled as non-standard if the deviation of the dimension from the nominal is more than 10% of the nominal d
30、imension. JEDEC Standard No. 51-2A Page 3 4 Environmental conditions for natural convection measurements (contd) 4.2 Test fixture support The support fixture shall be constructed per Figures 1, 2, and 3. The package shall be positioned in the geometric center of the chamber by adjusting the position
31、 of the support structure as necessary. The material used for the fixture shall be a low thermal conductivity material as detailed in 4.6.2. There shall be no structures above the package and board being tested to avoid disturbing the convection plume unless it can be proved that the deviation cause
32、s less than a 2% change in the measured thermal resistances. Alternate structures for mounting the connector and board are acceptable if it can be demonstrated that the measured thermal resistances are within 2% of the values measured with this reference design. NOTE 1 Dimensions in mm. NOTE 2 Wirin
33、g not shown, but will be placed to avoid interfering with the convection air flow. Figure 1 Side view of the test fixture and enclosure JEDEC Standard No. 51-2A Page 4 4 Environmental conditions for natural convection measurements (contd) 4.2 Test fixture support (contd) NOTE 1 Dimensions in mm. Fig
34、ure 2 End view of test fixture and enclosure Figure 3 Isometric view of the test board and fixture without the enclosure JEDEC Standard No. 51-2A Page 5 4 Environmental conditions for natural convection measurements (contd) 4.3 Edge connector and printed circuit board support The socket shall accomm
35、odate the printed circuit board. The board must be horizontal within +/- 5 degrees. If the edge connector and socket do not provide adequate support, it may be necessary to provide additional support such as a rod with diameter less than 3.5 mm to support the end of the board. The rod must be made o
36、f a low-thermal-conductivity material (less than 0.5 W/m K) or must be thermally insulated from the board. 4.4 Ambient temperature thermocouple The wire diameter shall be no larger than AWG size 30 (or no larger than 0.26 mm diameter). Placement of the thermocouple shall be 25 +/- 5 mm below the bot
37、tom plane of the printed circuit test board and 25 +/- 5 mm from the side wall. Refer to Figures 1, 2, and 3. The accuracy of the thermocouple and associated measuring system shall be 1C or better. 4.5 Test board The test board defined by the JESD51 series of specifications shall be used for the the
38、rmal measurement. The board used shall be referenced when the thermal performance is specified by both the JEDEC specification and the short reference. Table 1 lists the packages, appropriate JEDEC board specification and the suggested short reference name that would be used when reporting data. Tab
39、le 1 Thermal test boards Package Specification Short Reference JESD51-3 1s Board Leaded Surface Mount, Peripheral Leads (e.g. QFP) JESD51-7 2s2p Board JESD51-3 plus JESD51-5 1s Board Leaded Surface Mount Peripheral Leads with direct thermal attach (e.g. exposed pad QFP) JESD51-7 plus JESD51-5 2s2p B
40、oard JESD51-3 plus JESD51-5 1s Board Leadframe based perimeter array with direct thermal attach (e.g. QFN) JESD51-7 plus JESD51-5 2s2p Board JESD51-9 1s Board Array surface mount (e.g. BGA, or LGA JESD51-9 2s2p Board JESD51-10 1s Board Through Hole Perimeter Array (e.g. DIP) JESD51-10 2s2p Board JES
41、D51-11 1s Board Through Hole Array (e.g. PGA) JESD51-11 2s2p Board Table 1 lists the thermal test boards standardized under the JESD51 series of specifications at the time that this specification was updated. Refer to the JESD51 overview document for a current list of standardized boards. JEDEC Stan
42、dard No. 51-2A Page 6 4 Environmental conditions for natural convection measurements (contd) 4.6 Material The suggested construction materials listed in this document are intended as a guideline and are not all-inclusive. 4.6.1 Enclosure (box) The following materials, or their thermal equivalent, ha
43、ve been and may be used for construction of the enclosure: cardboard, polycarbonate, polypropylene, wood, and plywood. Each of these materials has a low thermal conductivity (less than 0.5 W/m K) and high infrared emissivity. Minimum wall thickness of 3 mm is required. 4.6.1.1 Considerations for cha
44、nges in room temperature The room ambient temperature when the tests are conducted shall be between 15C and 30C. If the room in which the testing occurs suffers from drastic temperature changes (3C), then placement of a larger box over the test enclosure should be considered. Thicker test enclosure
45、walls should also be considered. 4.6.2 Test fixture The following materials, or their thermal equivalent, may be used for construction of the support structure: plywood, wood, polycarbonate, or polypropylene. Each of these materials has a low thermal conductivity. Common fasteners and adhesives may
46、be used in the construction. 5 Thermal measurement procedure and methodology This section details the steps necessary to perform a thermal resistance measurement in a natural convection (still air) environment. The following equations describe the measured and calculated parameters required for maki
47、ng a thermal measurement for a single chip (die) package with one heat source 5.1 Methodology The junction-to-ambient thermal resistance (RJA or JA or Theta-JA) is determined from equation 1: JA= (TJ- TA)/ PH(1) where JA= thermal resistance from junction-to-ambient (C/W) TJ= junction temperature whe
48、n the device has achieved a steady-state after application of PH (C) TA= ambient temperature (C) PH= power dissipation that produced change in junction temperature (W) JEDEC Standard No. 51-2A Page 7 5 Thermal measurement procedure and methodology (contd) 5.1 Methodology (contd) As described in the
49、JESD51-1, a temperature-sensitive parameter (TSP) is used to sense the change in temperature of the junction operating area due to the application of electrical power to the device. In equation terms, TJ= (TSP x K) (2) where TSP = change in the TSP caused by the application of PH K = K factor, which is the ratio of junction temperature change to temperature-sensitive parameter change in the linear region of the temperature-sensitive parameter - temperature relationship. The junction-to-ambient thermal resistance can
