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

IEC TR 63091:2017(E) is a technical report and is applicable to SMB 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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Status
Published
Publication Date
23-May-2017
Current Stage
PPUB - Publication issued
Start Date
24-May-2017
Completion Date
24-May-2017
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IEC TR 63091:2017 - Study for the derating curve of surface mount fixed resistors - Derating curves based on terminal part temperature
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IEC TR 63091
Edition 1.0 2017-05
TECHNICAL
REPORT
Study for the derating curve of surface mount fixed resistors – Derating curves
based on terminal part temperature
IEC TR 63091:2017-05(en)
---------------------- Page: 1 ----------------------
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IEC TR 63091
Edition 1.0 2017-05
TECHNICAL
REPORT
Study for the derating curve of surface mount fixed resistors – Derating curves
based on terminal part temperature
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.040.10 ISBN 978-2-8322-4368-8

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 63091:2017 © IEC 2017
CONTENTS

FOREWORD ........................................................................................................................... 7

INTRODUCTION ..................................................................................................................... 9

1 Scope ............................................................................................................................ 10

2 Normative references .................................................................................................... 10

3 Terms and definitions .................................................................................................... 10

4 Study for the derating curve of surface mount fixed resistors ......................................... 11

4.1 General ................................................................................................................. 11

4.2 Using the derating curve based on the terminal part temperature .......................... 12

4.3 Measuring method of the terminal part temperature of the SMD resistor ............... 13

4.4 Measuring method of the thermal resistance R from the terminal part
th shs-t

to the surface hotspot ........................................................................................... 19

4.5 Conclusions .......................................................................................................... 21

Annex A (informative) Background of the establishment of the derating curve based

on ambient temperature ........................................................................................................ 22

A.1 Tracing the history of the mounting and heat dissipation figuration of

resistors ................................................................................................................ 22

A.2 How to establish the high temperature slope part of the derating curve ................. 24

A.2.1 General ......................................................................................................... 24

A.2.2 Derating curve for the semiconductors ........................................................... 26

A.2.3 Derating curve for resistors ............................................................................ 29

Annex B (informative) The temperature rise of SMD resistors and the influence of the

printed circuit board .............................................................................................................. 40

B.1 Temperature rise of SMD resistors ........................................................................ 40

B.2 The influence of the printed circuit boards ............................................................. 45

Annex C (informative) The influence of the number of resistors mounted on the test

board .................................................................................................................................... 49

C.1 General ................................................................................................................. 49

C.2 The influence of the number of resistors mounted on the test board ...................... 49

C.3 The delay of correspondence for current products with nonstandard

dimensions ........................................................................................................... 51

Annex D (informative) Influence of the air flow in the test chamber ...................................... 52

D.1 General ................................................................................................................. 52

D.2 Influence of the wind speed .................................................................................. 52

Annex E (informative) Validity of the new derating curve ...................................................... 60

E.1 Suggestion for establishing the derating curve based on the terminal part

temperature .......................................................................................................... 60

E.2 Conclusion ............................................................................................................ 65

Annex F (informative) The thermal resistance of SMD resistors ........................................... 67

Annex G (informative) How to measure the surface hotspot temperature ............................. 72

G.1 Target of the measurement ................................................................................... 72

G.2 Recommended measuring equipment ................................................................... 72

G.3 Points to be careful when measuring the surface hotspot of the resistor with

an infrared thermograph ........................................................................................ 72

G.3.1 General ......................................................................................................... 72

G.3.2 Spatial resolution and accuracy of peak temperature measurement ............... 73

G.3.3 Influence of the angle of the measurement target normal line and the

infrared thermograph light axis ...................................................................... 75

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IEC TR 63091:2017 © IEC 2017 – 3 –

Annex H (informative) How the resistor manufacturers measure the thermal resistance

of resistors ............................................................................................................................ 79

H.1 The measuring system .......................................................................................... 79

H.2 Definition of the two kinds of temperatures............................................................ 80

H.3 Errors in the measurement .................................................................................... 83

Annex I (informative) Measurement method of the terminal part temperature of the

SMD resistors ....................................................................................................................... 88

I.1 Measuring method using an infrared thermograph ................................................. 88

I.2 Measuring method using the thermocouple ........................................................... 89

I.3 Estimating the error range of the temperature measurement using the

thermal resistance of the thermocouple ................................................................. 90

I.3.1 General ......................................................................................................... 90

I.3.2 When using the type T thermocouples ........................................................... 97

I.4 Thermal resistance of the board ............................................................................ 97

I.5 Conclusion of this annex ..................................................................................... 100

Annex J (informative) The variation of the heat dissipation fraction caused by the

difference between the resistor and its mounting configuration ........................................... 101

J.1 Heat dissipation ratio of cylindrical resistors wired in the air................................ 101

J.2 Heat dissipation ratio of SMD resistors mounted on the board ............................ 102

J.3 Heat dissipation ratio of the cylindrical resistors mounted on the through-

hole printed board ............................................................................................... 104

Annex K (informative) Influence of airflow on SMD resistors .............................................. 105

K.1 General ............................................................................................................... 105

K.2 Measurement system .......................................................................................... 105

K.3 Test results (orthogonal) ..................................................................................... 106

K.4 Test results (parallel) .......................................................................................... 110

Annex L (informative) The influence of the spatial resolution of the thermograph ............... 115

L.1 The application for using the thermograph when measuring the temperature

of the SMD resistor ............................................................................................. 115

L.2 The relation between the minimum area that the accurate temperature could

be measured and the pixel magnification percentage .......................................... 115

L.3 Example of the RR1608M SMD resistor hotspot's actual measurement ............... 120

L.4 Conclusion .......................................................................................................... 121

Annex M (informative) Future subjects ............................................................................... 122

Bibliography ........................................................................................................................ 123

Figure 1 – Existing derating curve based on ambient temperature ........................................ 12

Figure 2 – Suggested derating curve based on terminal temperature .................................... 12

Figure 3 – Attachment position of the thermocouple when measuring the temperature

of the terminal part ................................................................................................................ 13

Figure 4 – Attaching type K thermocouples ........................................................................... 14

Figure 5 – Wiring routing of the thermocouple ....................................................................... 15

Figure 6 – The true value and the actual measured value of the terminal part

temperature .......................................................................................................................... 16

Figure 7 – Thermal resistance R of the FR4 single side board (thickness 1,6 mm)........ 17

th eq

Figure 8 – Length that cause the heat dissipation and the thermal resistance of the

type-K thermocouple (calculated) .......................................................................................... 18

Figure 9 – Example of calculation of the measurement error ∆T caused by the heat

dissipation of the thermocouple ............................................................................................ 19

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– 4 – IEC TR 63091:2017 © IEC 2017
Figure 10 – Recommended measurement system of T and T for calculating R
shs t th

..................................................................................................................................... 20

shs-t

Figure A.1 – Wired in the air using the lug terminal ............................................................... 22

Figure A.2 – Heat path when wired in the air using the lug terminal ...................................... 23

Figure A.3 – Test condition for resistors with category power 0 W ......................................... 24

Figure A.4 – Test condition for resistors with category power other than 0 W ........................ 25

Figure A.5 – Example of reviewing the derating curve ........................................................... 26

Figure A.6 – T , T and R of transistors .......................................................................... 27

j c th j-c

Figure A.7 – Derating curves for transistors .......................................................................... 28

Figure A.8 – Trajectory of T when P is reduced according to the derating curve ................... 29

Figure A.9 – Leaded resistors with small temperature rise .................................................... 30

Figure A.10 – Leaded resistors with large temperature rise ................................................... 31

Figure A.11 – Trajectory of T for the lead wire resistors with small temperature rise .......... 31

Figure A.12 – Trajectory of T for the lead wire resistors with large temperature rise .......... 33

Figure A.13 – Trajectory of T for resistors with category power other than 0 W .................. 34

Figure A.14 – T and MAT for lead wire resistors with large temperature rise ...................... 35

Figure A.15 – T and MAT for lead wire resistors with small temperature rise ..................... 36

Figure A.16 – Resistors for which the hotspot is the thermally sensitive point ....................... 37

Figure A.17 – Resistor that have derating curve similar to the semiconductor ....................... 38

Figure B.1 – Temperature distribution of the SMD resistors mounted on the board ............... 41

Figure B.2 – Temperature rise of the SMD resistors from the ambient temperature ............... 42

Figure B.3 – Measurement system layout and board dimension ............................................ 43

Figure B.4 – Temperature rise of RR2012M (thickness 35 μm, 0,25 W applied) .................... 44

Figure B.5 – Temperature rise of RR2012M (thickness 70 μm, 0,25 W applied) .................... 45

Figure B.6 – Trajectory of the terminal part and hotspot temperature of the SMD

resistors ................................................................................................................................ 46

Figure B.7 – Operating temperature of the resistor on the board with narrow patterns........... 47

Figure C.1 – Test board compliant with the IEC standard for RR1608M ................................ 50

Figure C.2 – Relation between the number of samples and the surface hotspot

temperature rise ................................................................................................................... 50

Figure C.3 – Infrared thermograph image in the same scale when power is applied to 5

samples and 20 samples ....................................................................................................... 51

Figure D.1 – Wind speed and the terminal part temperature rise of the RR6332M ................. 53

Figure D.2 – Test system for the natural convection flow ...................................................... 53

Figure D.3 – Observing the influence of the agitation wind in the test chamber ..................... 55

Figure D.4 – Wind speed and the terminal part temperature rise of the RR5025M ................. 56

Figure D.5 – Wind speed and the terminal part temperature rise of the RR3225M ................. 56

Figure D.6 – Wind speed and the terminal part temperature rise of the RR3216M ................. 57

Figure D.7 – Wind speed and the terminal part temperature rise of the RR2012M ................. 57

Figure D.8 – Wind speed and the terminal part temperature rise of the RR1608M ................. 58

Figure D.9 – Wind speed and the terminal part temperature rise of the RR1005M ................. 58

Figure E.1 – Derating conditions of SMD resistors on the resistor manufacturer test

board .................................................................................................................................... 60

Figure E.2 – New derating curve provided by the resistor manufacturer to the

electric/electronic designers .................................................................................................. 63

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IEC TR 63091:2017 © IEC 2017 – 5 –

Figure E.3 – Derating curve based on the terminal part temperature ..................................... 64

Figure E.4 – Derating curve based on the terminal part temperature ..................................... 65

Figure F.1 – Definition of the thermal resistance in a strict sense .......................................... 68

Figure F.2 – Thermal resistance of the resistor ..................................................................... 69

Figure G.1 – Difference of the measured hotspot temperature caused by the spatial

resolution .............................................................................................................................. 74

Figure G.2 – Measuring system for the error caused by the angle ......................................... 76

Figure G.3 – Error caused by the angle of the optical axis and the target surface

(natural convection) .............................................................................................................. 77

Figure G.4 – Error caused by the angle of the optical axis and the target surface (0,3

m/s air ventilation from the side) ........................................................................................... 77

Figure H.1 – Measuring system for calculating the thermal resistance between the

surface hotspot and the terminal part .................................................................................... 80

Figure H.2 – Simulation model .............................................................................................. 81

Figure H.3 – Temperature distribution of the copper block surface (calculated) ..................... 84

Figure H.4 – Isothermal line of the fillet part (calculated) ...................................................... 86

Figure I.1 – Temperature drop caused by the attached thermocouple ................................... 89

Figure I.2 – Example of the printed board ............................................................................. 90

Figure I.3 – Printed board shown with the thermal network ................................................... 91

Figure I.4 – Equivalent circuit of the printed board shown with the thermal network ............. 92

Figure I.5 – Equivalent circuit when the thermocouple is connected ...................................... 93

Figure I.6 – Ambient temperature and the space need for the heat dissipation of the

thermocouple ........................................................................................................................ 94

Figure I.7 – Equivalent circuit when the thermocouple is connected ...................................... 95

Figure I.8 – Length that causes the heat dissipation and the thermal resistance of the

type K thermocouple (calculated) .......................................................................................... 96

Figure I.9 – Length that cause the heat dissipation and the thermal resistance of the

type T thermocouple (calculated) .......................................................................................... 97

Figure I.10 – Thermal resistance R of the FR4 single side board (thickness 1,6 mm) .... 98

th eq

Figure I.11 – Calculating the thermal resistance of the board from the fillet side .................. 99

Figure J.1 – Simulation model of the lead wire resistors wired in the air .............................. 101

Figure J.2 – Heat dissipation ratio of the leaded cylindrical resistors (calculated) ............... 102

Figure J.3 – Measurement system of the heat dissipation ratio of SMD resistors

mounted on the board ......................................................................................................... 103

Figure K.1 – Measurement system ...................................................................................... 106

Figure K.2 – Relationship between the terminal part temperature rise and the wind

speed for the RR6332M (orthogonal) .................................................................................. 107

Figure K.3 – Relationship between the terminal part temperature rise and the wind

speed for the RR5025M (orthogonal) .................................................................................. 107

Figure K.4 – Relationship between the terminal part temperature rise and the wind

speed for the RR3225M (orthogonal) .................................................................................. 108

Figure K.5 – Relationship between the terminal part temperature rise and the wind

speed for the RR3216M (orthogonal) .................................................................................. 108

Figure K.6 – Relationship between the terminal part temperature rise and the wind

speed for the RR2012M (orthogonal) .................................................................................. 109

Figure K.7 – Relationship between the terminal part temperature rise and the wind

speed for the RR1608M (orthogonal) .................................................................................. 109

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– 6 – IEC TR 63091:2017 © IEC 2017

Figure K.8 – Relationship between the terminal part temperature rise and the wind

speed for the RR1005M (orthogonal) .................................................................................. 110

Figure K.9 – Relationship between the terminal part temperature rise and the wind

speed for the RR6332M (parallel) ....................................................................................... 111

Figure K.10 – Relationship between the terminal part temperature rise and the wind

speed for the RR5025M (parallel) ....................................................................................... 111

Figure K.11 – Relationship between the terminal part temperature rise and the wind

speed for the RR3225M (parallel) ....................................................................................... 112

Figure K.12 – Relationship between the terminal part temperature rise and the wind

speed for the RR3216M (parallel) ....................................................................................... 112

Figure K.13 – Relationship between the terminal part temperature rise and the wind

speed for the RR2012M (parallel) ....................................................................................... 113

Figure K.14 – Relationship between the terminal part temperature rise and the wind

speed for the RR1608M (parallel) ....................................................................................... 113

Figure K.15 – Relationship between the terminal part temperature rise and the wind

speed for the RR1005M (parallel) ....................................................................................... 114

Figure K.16 – Terminal part temperature rise of RR6332M, difference between the

windward and leeward sides when placed parallel .............................................................. 114

Figure L.1 – Step response of the Gaussian filter of the various cut-off spatial

frequencies (calculated) ...................................................................................................... 116

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 .................................... 117

Figure L.3 – Measuring system of spatial frequency filter of the infrared thermograph ......... 118

Figure L.4 – Actual measured value of the step response of various magnifier lenses ......... 119

Figure L.5 – Comparison of the actual measured value and the calculated value (step

response) ........................................................................................................................... 120

Figure L.6 – Comparison of the actual measured value and the calculated value

(surface hotspot of the resistor) .......................................................................................... 121

Table D.1 – Number of samples mounted and the applied power .......................................... 54

Table H.1 – Results of the fillet part temperature simulation (calculated value) ..................... 82

Table H.2 – Simulation result of the fillet part's temperature where it is measurable

(calculated value) ................................................................................................................. 82

Table H.3 – Simulation result of the fillet part's temperature where it is measurable

(calculated value) ................................................................................................................. 83

Table H.4 – Thermal resistance simulation results between the surface hotspot and the

terminal part based on the copper block temperature (calculated value) ............................... 85

Table J.1 – Analysis result of the heat dissipation ratio of SMD resistors (calculated

value and value actually measured) .................................................................................... 104

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IEC TR 63091:2017 © IEC 2017 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
STUDY FOR THE DERATING CURVE
OF SURFACE MOUNT FIXED RESISTORS –
Derating curves based on terminal part temperature
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