大功率LED制造与封装技术005

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Kir

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金丝与16

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铝（硅铝）丝键合系统

Pure aluminum is too soft. So alloyed with 1% Si or 1% Mg to provide a solid-solution strengthening mechanism.

Al-OFHC Cu Al-Ag plated LF Al-Ni

>75um Al can be used for power devices.

Institute of Microelectronics

Al(OH)3+ Cl -→Al(OH)2+ OH -Al + 4Cl -→Al(Cl)4-2AlCl 4-+ 6H 2O →2Al(OH)3+ 6H ++ 8Cl -

Institute of Microelectronics

键合丝的要求

表面洁净光滑

长丝、单层、单根密绕

严格包装和储存

10-15°C,20-50%RH

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提高

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模塑的基本工艺

模塑料通常为热固性塑料

9热固性：在加热固化后不会再次受热软化

9热塑性：在加热塑化后如果再次受热还会再次软化

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模塑料的基本构成

基体（10-30%）

（高分子化合物树脂）

添加剂（60-90%）

环氧树脂硅酮树脂

1,2-聚丁二烯酯树脂

固化剂催化剂

填充剂（SiO 2）阻燃剂脱模剂染色剂

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主

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性能检28

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模塑料的类型（p.32）

普通型

快速固化型无后固化型高热导型低应力型低辐射型低膨胀型低翘曲型

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普30

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低应力型模塑料

固化过程产生的收缩应力温度变化时的热应力热应力导致失效?开裂

温度变化时的热应力?弹性模量↓?线膨胀系数↓

?玻璃化转变温度↓

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考32

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模

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引线框架的功能

电连接

9对内依靠键合实现芯片与外界的信号连接

9依靠焊点与电路板连接

机械支撑和保护

9对芯片起到支持

9与外壳或模塑料实现保护

散热

9散热通道

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不同封36

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引线框架材料的要求

热匹配

良好的机械性能导热性能好

使用过程无相变材料中杂质少低价

加工特性和二次性能好

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常见引线38

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引线框架材料的主要物理性能

8.9

8.12

8.17

比重（g/cm

）

120001500013400弹性模量(kg/mm 2)6534导电率(%IACS) 2.630.150.19导热系数(W/cm °

C)16.3

4.4-

5.6

4.5-

5.5

线膨胀系数(10-6/ °C,20-350°C)109014271450熔点(°C)400650---软化温度(°C)456553抗弯强度(kg/mm 2)194 Alloy 4J424J29

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K 40

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42 Alloy

具有与Kovar合金类似性能的框架材料（封接材料）

采用Ni的添加取代Co 去应力退火

线膨胀系数与Kovar合金相近

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引线框架的成型

冲压型蚀刻型

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引线框架的质量标准

)引线键合区

)几何尺寸、表面涂敷、引线扭曲、平整

度、共面性

)

芯片粘接区

)几何尺寸、表面涂敷、粗糙度

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芯片粘接的基本概念

Chip Attachment/Bonding，通常采用粘接技术实现管芯（IC Chip）与底座

（Chip Carrier）的连接

机械强度、化学性能稳定、导电、导热、热匹配、低固化温度、可操作性

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环氧树脂粘接技术

工艺简单、成本低廉

适合于大规模生产，质量上已经接近Au-Si共晶焊水平可以分为两类：

导电、导热胶—“导电胶” 导热、电绝缘胶

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导电

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固化条件

一般固化温度在150°C左右，固化

时间约1hr

固化前：“导电胶”不导电

固化后：溶剂挥发、银粉相互紧密接触形成导电链

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基板材料的性能

电

介电常数、功耗、电阻、…

…

热

热导率、热膨胀系数、热稳定性、……

物理

表面平整度、表面光洁度

化学

化学稳定、低孔隙率、高纯度

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氧化铝54

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其它陶瓷基板材料

氧化铍（BeO）

热导率8倍于氧化铝，用于功率器件贵毒

氮化铝（AlN）

高热导率，用于替代氧化铍与Si相近的热膨胀系数低价（与氧化铍比较）

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其它

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主要陶瓷基板材料基本性能

55.2-69.0

55.2-69.0----230与含量相关拉伸强度（M Pa ）6.2

5.5-.7.58.5-10

6.7-8.94.5-10介电常数（@1MHz）11

2.1-4.2

镁橄榄石

8.6-10.52.1-2.5滑石 4.3-4.782-320AlN 6.3-7.5150-300BeO 4.3-7.415-33Al 2O 3CTE

（ppm/°C）热导率

（W/m°C）

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Process flow of LTCC

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MCM高

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焊接材料

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微电子

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钎焊技术

软钎焊（<450°C）

Sn-Pb 低温焊料

硬钎焊

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焊料

Heat

Solder

Flux 66

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Sn-P

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Flip

Chip

Eutectic Pb-Sn

Ni/Au UBM

Lead rich layer

Eutectic Pb-Sn

IMC

Ni3P

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Lead Consumption in Industry

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Histo

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Lead Free in Europe

?The primary drivers for lead are thought to be from Europe and Japan.The proposal is entitled the Waste Electrical and Electronic Equipment (WEEE) Directive.

Prevention : the use of lead as well as several other toxic materials should be phased out by January 1, 2004.

Separate Collection : ensure that new products offer a “take-back”recycling to private households as well as other holders free of charge.

Treatment : treatment of waste from electrical and electronic equipment.

Recovery : ensure producers are setup to re-use and recycle a certain percentage of the waste from electrical and electronic equipment depending on the product [ICER].

Institute of Microelectronics Lead

?There is currently no federal legislation in Japan directed towards banning the use of lead in electronics.

The Japanese Home Electronics Recycling Law requires OEMs to collect and recycle four major products by April 1, 2001. Although lead was not specifically mentioned, the Japanese EPA and the government suggest reducing the use of lead as part of their increased recycling initiatives.

?The Japanese Ministry of International Trade and Industry (MITI)has recommended that the use of lead be reduced by half by the year 2000 and by two-thirds by 2005.

The Japan Institute for Electronic Packaging (JIEP) recommends mass production using Pb-free solder during 1999-2000, full scale recycling of assembly boards by 2001-2002, adoption of Pb-free solders in reflow soldering processes by 2001, Pb-containing solder used only exceptionally by 2005-2010, and complete elimination of Pb solder by 2010-2015.

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Criteria for Lead Free Solder

No negative environmental impact now or in the

future

Sufficient quantities of the elements Low cost

Similar melting temperature to that of Sn-Pb solders

Eutectic Sn63-Pb37 (183°C) Physical properties, Fatigue resistance Adequate wettability

Compatibility with existing parts and processes Ideally available in all forms i.e. bar, paste and wire Adequate shelf life and performance

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无

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For Lead-Free, Besides Marketing,

What is the Most Technical Concern? Currently ,

SnPb solders (MP ￣ 183o C)For lead-free soldering ,

SnAgCu solders (MP ￣ 217o C)

Thus, the components and PCB will be subjected to much higher temperatures during leadfree soldering and their reliability is of great concern!

无铅带来的工艺问题

Institute of Microelectronics

Lead fr

Preheat Zone Ramp below 4°C/Sec

Time is flexible

Soak Zone

Ramp from 170 -200°C Typically 60 –90 secs

Ramp Zone

From 200°C to reflow peak in 60 –90 Secs

Reflow Zone 225-235°C

Time above reflow 30-60

secs

Time

Process Window is Narrower

Cooling to 125°C

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Some Lead Free Solder Alloys

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Melting P

Alloy System

Composition Melting Range

Sn-Pb 60Sn-40Pb

183-188Sn-Cu Sn-0.7Cu 227Sn-Ag-Bi Sn-3.5Ag-3Bi 206-213Sn-Ag-Cu Sn-3.8Ag-0.7Cu 217Sn-Ag

Sn-3.5Ag

221

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Sn-Ag-Cu

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