热分析的基本参数与概念

2021年2月28日发(作者：离线)

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Executive Summary

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Title of document

Table of Contents

1

Introduction .......................... .................................................. .................................. 3

1.1

2

基本参数介绍

..................... .................................................. ............................. 3

Activities

.

..... .................................................. .................................................. ......... 4

2.1

Theta-ja (

θ

ja)Junction-to-Ambient

.

.............................. ....................................... 4

2.1.1

测量方法

....................... .................................................. ........................... 4

2.1.2

节温计算公式

..................... .................................................. ...................... 6

2.2

Theta-jc (

θ

jc) Junction-to-Case

< p>
.

................................ ......................................... 6

2.2.1

测量方法

....................... .................................................. ........................... 6

2.2.2

节温计算公式

..................... .................................................. ...................... 6

2.2.3

θ

jc

与

θ

ja

的关系

.

........... .................................................. .............................. 7

2.3

Theta-jb (

θ

jb) Junction-to-Board .... .................................................. .................. 7

2.3.1

测量方法

....................... .................................................. ........................... 8

?????

节温计算公式

..................... .................................................. ...................... 8

2.3.3

θ

jc

与

θ

ja

的关系

.

........... .................................................. .............................. 8

???

Ψ

的含义

.

....................................... .................................................. .................. 9

2.4.1

Ψ

jb ........................ .................................................. ................................... 9

2.4.2

Ψjc

........................ .................................................. ................................... 9

2.5

各种封装的散热效果

.

............................................. ............................................ 9

2.5.1

TI PowerPAD

封装的使用注意事项

.

..................................... ..................... 10

3

Results

.............................................. .................................................. ................... 12

3.1

关于

θ

ja

θ

jc

Ψ

JB

,

Ψ

JT

使用问题

.......... .................................................. ............... 12

4

Discussion

.

............................... .................................................. ............................ 12

4.1

热仿真软件的使用

................... .................................................. ...................... 12

5

Conclusions ... .................................................. .................................................. .... 12

5.1 ................ .................................................. .................................................. ......... 12

6

Abbreviations, Definitiones, Glossary < /p>

........................................ ............................. 13

6.1 ................................... .................................................. ........................................ 13

7

Version

.

........ .................................................. .................................................. ...... 13

< p>
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Title of document

Contents

1

Introduction

1.1

基本参数介绍

一般包括三个参数

??

?

ja

??< /p>

θ

jc

,

?

θ

jb

，三种参数所指的散热图示如下。< /p>

Ta

，

Tb

，

Tc

的测试点如下：

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Tc:

< p>
芯片外壳的温度（其中

Tt

指芯片顶部，

Tp

指芯片底部。于

Tc

通用）

Tb

：芯片管脚接触于

PCB

处温度

Ta:

芯片周围空气温度

Tj:

芯片内部

PN

< p>
节温度，此温度一般＜

150

℃，否则造成芯片烧 毁。

2

Activities

2.1

Theta-ja (

θ

ja

)Junction-to- Ambient

PN

节到空气的热阻。单位℃

/ W

。

2.1.1

测量方法

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器件说明书中的

< br>ΦJA

是根据

JESD51

标准 给出的，其标准环境是指将器件安装在较大的

印刷电路板上，并置于

1

立方英尺的静止空气中。

Θ< /p>

ja

与

PCB

叠 层结构、芯片焊盘大小、高度等均有关系，故因此说明书中的数值（实验室

数据）没有太 大的参考价值。但目前只能如此计算。

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2.1.2

节温计算公式

T

junction

??

T

ambient

????

?

ja

??

Power

?

；

??

< /p>

T

ambient

：环境温度

< p>

T

junction

： 芯片

PN

节温度

Power

：芯片消耗功率

2.2

Theta-jc (

θ

jc

) Junction- to-Case

θ

JC

是结到管壳的 热阻，管壳可以看作是封装外表面的一个特定点。此参数最是为预估有

散热器的器件设计 的。

2.2.1

测量方法

2.2.2

节温计算公式

T

junction

=T

case

+

??

θ

< br>jc

* Power

??

?< /p>

T

case

：芯片外壳温度

T

junction

：芯 片

PN

节温度

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