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BSI PD IEC/TR 63091:2017

BSI PD IEC/TR 63091:2017

$215.11

Study for the derating curve of surface mount fixed resistors. Derating curves based on terminal part temperature

Published By Publication Date Number of Pages
BSI 2017 126
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This Technical Report is applicable to SMD resistors with sizes equal or smaller than the RR6332M, including the typical rectangular and cylindrical SMD resistors mentioned in IEC 60115-8.

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PDF Pages PDF Title
2 undefined
4 CONTENTS
9 FOREWORD
11 INTRODUCTION
12 1 Scope
2 Normative references
3 Terms and definitions
13 4 Study for the derating curve of surface mount fixed resistors
4.1 General
14 4.2 Using the derating curve based on the terminal part temperature
Figures
Figure 1 – Existing derating curve based on ambient temperature
Figure 2 – Suggested derating curve based on terminal temperature
15 4.3 Measuring method of the terminal part temperature of the SMD resistor
Figure 3 – Attachment position of the thermocouple when measuring the temperature of the terminal part
16 Figure 4 – Attaching type K thermocouples
17 Figure 5 – Wiring routing of the thermocouple
18 Figure 6 – The true value and the actual measured value of the terminal part temperature
19 Figure 7 – Thermal resistance Rth eq of the FR4 single side board (thickness 1,6 mm)
20 Figure 8 – Length that cause the heat dissipation and the thermal resistance of the type-K thermocouple (calculated)
21 4.4 Measuring method of the thermal resistance Rth shs-t from the terminal part to the surface hotspot
Figure 9 – Example of calculation of the measurement error ∆T caused by the heat dissipation of the thermocouple
22 Figure 10 – Recommended measurement system of Tshs and Tt for calculating Rth shs-t
23 4.5 Conclusions
24 Annex A (informative) Background of the establishment of the derating curve based on ambient temperature
A.1 Tracing the history of the mounting and heat dissipation figuration of resistors
Figure A.1 – Wired in the air using the lug terminal
25 Figure A.2 – Heat path when wired in the air using the lug terminal
26 A.2 How to establish the high temperature slope part of the derating curve
A.2.1 General
Figure A.3 – Test condition for resistors with category power 0 W
27 Figure A.4 – Test condition for resistors with category power other than 0 W
28 A.2.2 Derating curve for the semiconductors
Figure A.5 – Example of reviewing the derating curve
29 Figure A.6 – Tj, Tc and Rth j-c of transistors
30 Figure A.7 – Derating curves for transistors
31 A.2.3 Derating curve for resistors
Figure A.8 – Trajectory of Tj when P is reduced according to the derating curve
32 Figure A.9 – Leaded resistors with small temperature rise
33 Figure A.10 – Leaded resistors with large temperature rise
Figure A.11 – Trajectory of Ths for the lead wire resistors with small temperature rise
35 Figure A.12 – Trajectory of Ths for the lead wire resistors with large temperature rise
36 Figure A.13 – Trajectory of Ths for resistors with category power other than 0 W
37 Figure A.14 – Tsp and MAT for lead wire resistors with large temperature rise
38 Figure A.15 – Tsp and MAT for lead wire resistors with small temperature rise
39 Figure A.16 – Resistors for which the hotspot is the thermally sensitive point
40 Figure A.17 – Resistor that have derating curve similar to the semiconductor
42 Annex B (informative) The temperature rise of SMD resistors and the influence of the printed circuit board
B.1 Temperature rise of SMD resistors
43 Figure B.1 – Temperature distribution of the SMD resistors mounted on the board
44 Figure B.2 – Temperature rise of the SMD resistors from the ambient temperature
45 Figure B.3 – Measurement system layout and board dimension
46 Figure B.4 – Temperature rise of RR2012M (thickness 35 μm, 0,25 W applied)
47 B.2 The influence of the printed circuit boards
Figure B.5 – Temperature rise of RR2012M (thickness 70 μm, 0,25 W applied)
48 Figure B.6 – Trajectory of the terminal part and hotspot temperature of the SMD resistors
49 Figure B.7 – Operating temperature of the resistor on the board with narrow patterns
51 Annex C (informative) The influence of the number of resistors mounted on the test board
C.1 General
C.2 The influence of the number of resistors mounted on the test board
52 Figure C.1 – Test board compliant with the IEC standard for RR1608M
Figure C.2 – Relation between the number of samples and the surface hotspot temperature rise
53 C.3 The delay of correspondence for current products with nonstandard dimensions
Figure C.3 – Infrared thermograph image in the same scale whenpower is applied to 5 samples and 20 samples
54 Annex D (informative) Influence of the air flow in the test chamber
D.1 General
D.2 Influence of the wind speed
55 Figure D.1 – Wind speed and the terminal part temperature rise of the RR6332M
Figure D.2 – Test system for the natural convection flow
56 Tables
Table D.1 – Number of samples mounted and the applied power
57 Figure D.3 – Observing the influence of the agitation wind in the test chamber
58 Figure D.4 – Wind speed and the terminal part temperature rise of the RR5025M
Figure D.5 – Wind speed and the terminal part temperature rise of the RR3225M
59 Figure D.6 – Wind speed and the terminal part temperature rise of the RR3216M
Figure D.7 – Wind speed and the terminal part temperature rise of the RR2012M
60 Figure D.8 – Wind speed and the terminal part temperature rise of the RR1608M
Figure D.9 – Wind speed and the terminal part temperature rise of the RR1005M
62 Annex E (informative) Validity of the new derating curve
E.1 Suggestion for establishing the derating curve based on the terminal part temperature
Figure E.1 – Derating conditions of SMD resistors on the resistor manufacturer test board
65 Figure E.2 – New derating curve provided by the resistor manufacturer to the electric/electronic designers
66 Figure E.3 – Derating curve based on the terminal part temperature
67 E.2 Conclusion
Figure E.4 – Derating curve based on the terminal part temperature
69 Annex F (informative) The thermal resistance of SMD resistors
70 Figure F.1 – Definition of the thermal resistance in a strict sense
71 Figure F.2 – Thermal resistance of the resistor
74 Annex G (informative) How to measure the surface hotspot temperature
G.1 Target of the measurement
G.2 Recommended measuring equipment
G.3 Points to be careful when measuring the surface hotspot of the resistor with an infrared thermograph
G.3.1 General
75 G.3.2 Spatial resolution and accuracy of peak temperature measurement
76 Figure G.1 – Difference of the measured hotspot temperature caused by the spatial resolution
77 G.3.3 Influence of the angle of the measurement target normal line and the infrared thermograph light axis
78 Figure G.2 – Measuring system for the error caused by the angle
79 Figure G.3 – Error caused by the angle of the optical axisand the target surface (natural convection)
Figure G.4 – Error caused by the angle of the optical axisand the target surface (0,3 m/s air ventilation from the side)
81 Annex H (informative) How the resistor manufacturers measure the thermal resistance of resistors
H.1 The measuring system
82 H.2 Definition of the two kinds of temperatures
Figure H.1 – Measuring system for calculating the thermal resistance between the surface hotspot and the terminal part
83 Figure H.2 – Simulation model
84 Table H.1 – Results of the fillet part temperature simulation (calculated value)
Table H.2 – Simulation result of the fillet part’s temperature where it is measurable (calculated value)
85 H.3 Errors in the measurement
Table H.3 – Simulation result of the fillet part’s temperature where it is measurable (calculated value)
86 Figure H.3 – Temperature distribution of the copper block surface (calculated)
87 Table H.4 – Thermal resistance simulation results between the surface hotspot and the terminal part based on the copper block temperature (calculated value)
88 Figure H.4 – Isothermal line of the fillet part (calculated)
90 Annex I (informative) Measurement method of the terminal part temperature of the SMD resistors
I.1 Measuring method using an infrared thermograph
91 I.2 Measuring method using the thermocouple
Figure I.1 – Temperature drop caused by the attached thermocouple
92 I.3 Estimating the error range of the temperature measurement using the thermal resistance of the thermocouple
I.3.1 General
Figure I.2 – Example of the printed board
93 Figure I.3 – Printed board shown with the thermal network
94 Figure I.4 – Equivalent circuit of the printed board shown with the thermal network
95 Figure I.5 – Equivalent circuit when the thermocouple is connected
96 Figure I.6 – Ambient temperature and the space need for the heat dissipation of the thermocouple
97 Figure I.7 – Equivalent circuit when the thermocouple is connected
98 Figure I.8 – Length that causes the heat dissipation and the thermal resistance of the type K thermocouple (calculated)
99 I.3.2 When using the type T thermocouples
I.4 Thermal resistance of the board
Figure I.9 – Length that cause the heat dissipation and the thermal resistance of the type T thermocouple (calculated)
100 Figure I.10 – Thermal resistance Rth eq of the FR4 single side board (thickness 1,6 mm)
101 Figure I.11 – Calculating the thermal resistance of the board from the fillet side
102 I.5 Conclusion of this annex
103 Annex J (informative) The variation of the heat dissipation fraction caused by the difference between the resistor and its mounting configuration
J.1 Heat dissipation ratio of cylindrical resistors wired in the air
Figure J.1 – Simulation model of the lead wire resistors wired in the air
104 J.2 Heat dissipation ratio of SMD resistors mounted on the board
Figure J.2 – Heat dissipation ratio of the leaded cylindrical resistors (calculated)
105 Figure J.3 – Measurement system of the heat dissipation ratio of SMD resistors mounted on the board
106 J.3 Heat dissipation ratio of the cylindrical resistors mounted on the through-hole printed board
Table J.1 – Analysis result of the heat dissipation ratio of SMD resistors (calculated value and value actually measured)
107 Annex K (informative) Influence of airflow on SMD resistors
K.1 General
K.2 Measurement system
108 K.3 Test results (orthogonal)
Figure K.1 – Measurement system
109 Figure K.2 – Relationship between the terminal part temperature rise and the wind speed for the RR6332M (orthogonal)
Figure K.3 – Relationship between the terminal part temperature rise and the wind speed for the RR5025M (orthogonal)
110 Figure K.4 – Relationship between the terminal part temperature rise and the wind speed for the RR3225M (orthogonal)
Figure K.5 – Relationship between the terminal part temperature rise and the wind speed for the RR3216M (orthogonal)
111 Figure K.6 – Relationship between the terminal part temperature rise and the wind speed for the RR2012M (orthogonal)
Figure K.7 – Relationship between the terminal part temperature rise and the wind speed for the RR1608M (orthogonal)
112 K.4 Test results (parallel)
Figure K.8 – Relationship between the terminal part temperature rise and the wind speed for the RR1005M (orthogonal)
113 Figure K.9 – Relationship between the terminal part temperature rise and the wind speed for the RR6332M (parallel)
Figure K.10 – Relationship between the terminal part temperature rise and the wind speed for the RR5025M (parallel)
114 Figure K.11 – Relationship between the terminal part temperature rise and the wind speed for the RR3225M (parallel)
Figure K.12 – Relationship between the terminal part temperature rise and the wind speed for the RR3216M (parallel)
115 Figure K.13 – Relationship between the terminal part temperature rise and the wind speed for the RR2012M (parallel)
Figure K.14 – Relationship between the terminal part temperature rise and the wind speed for the RR1608M (parallel)
116 Figure K.15 – Relationship between the terminal part temperature rise and the wind speed for the RR1005M (parallel)
Figure K.16 – Terminal part temperature rise of RR6332M, difference between the windward and leeward sides when placed parallel
117 Annex L (informative) The influence of the spatial resolution of the thermograph
L.1 The application for using the thermograph when measuring the temperature of the SMD resistor
L.2 The relation between the minimum area that the accurate temperature could be measured and the pixel magnification percentage
118 Figure L.1 – Step response of the Gaussian filter of the various cut-off spatial frequencies (calculated)
119 Figure L.2 – Temperature distribution (cross-section) when measuring the object that becomes high temperature only in the range of 0,2 mm in diameter
120 Figure L.3 – Measuring system of spatial frequency filter of the infrared thermograph
121 Figure L.4 – Actual measured value of the step response of various magnifier lenses
122 L.3 Example of the RR1608M SMD resistor hotspot’s actual measurement
Figure L.5 – Comparison of the actual measured value and the calculated value (step response)
123 L.4 Conclusion
Figure L.6 – Comparison of the actual measured value and the calculated value (surface hotspot of the resistor)
124 Annex M (informative) Future subjects
125 Bibliography

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BSI PD IEC/TR 63091:2017
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