一文解析flip chip工艺流程

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Flip Chip conductive method - connect to Substrate/PCB

1.Metal bump 金属凸块-C4 process(IBM)

2. Tape-Automated bonding 卷带接合-ACF process

3. Anisotropic conductive adhesives

异方向性导电胶 -ACP process

4.Polymer bump 高分子凸块 - C4 process

5.Stud bump. 打线成球 - ACP process(Matsushita)

C4: controlled collapse chip connection

ACF: anisotropic conductive film

ACP(ACA): anisotropic conductive Adhesive paste

Various flip chip technologies

PS: WIT ( Wire interconnect technology)

TAB(Tape- automated bonding)

Various flip chip technologies

SBB Process

C4: Controlled Collapse Chip Connection Process

ACP: Anisotropic Conductive Paste Process

ACF: Anisotropic Conductive Film Process

Wafer Bump

Metal bump method

1. 蒸镀 Evaporation 

2. 溅镀 Sputter 

3. 电镀 Electroplating

4. 印刷 Printed solder paste bump

5. 锡球焊接 Solder ball bumping or Stud bump bonding (SBB)

6.无电镀镍 Electroless nickel technologies

Material of solder bump

1.95Sn/5Pb,97Sn/3Pb 高温锡铅合金

2. 63Sn/37Pb 低温锡铅合金

3. Ni 镍

4. Au 金 

5.Cu 铜

Wafer bump (Printed method) Process:Wafer clean

Silicon Wafer arrives with an aluminum based final metal pad and die passivation. Wafer can be probed prior to bumping.

Wafer Bump (Printed method) Process: Sputter UBM

The Under Bump Metallurgy is added by FCT through sputtered layers of Al,Ni-V,&Cu

Wafer Bump (Evaporation method)

Process: Sputter UBM

UBM consist 3 layer:

1. Adhesion layer : Ti,Cr,TiW 提供铝垫(Al pad)与护层(Passivation layer)有较强之黏着性

2. Wetting layer:Ni,Cu,Mo,Pt 高温回焊时锡球可完全沾附而成球

3. Protective layer:Au 保护 Ni,Cu等免于被氧化.

Wafer Bump (Printed method)

Process:Photo-resist

Apply photoresist, Pattern and develop

Wafer Bump (Printed method)

Process: Etch UBM

Etch to form UBM cap

Wafer Bump (Printed method) 

Process: Print solder paste & reflow

Deposit solder paste and reflow to form bump

Wafer Bump (Printed method)

Process: Inspection

Sample measure bump height, bump shear and bump resistance.

The typical size of a bump before reflow :

1. Evaporative bumps are 125 mils in diameter and 100 mils high.

2. Plated bumps are 125 - 175 mils in diameter and 25 -100 mils high.

上芯片流程Flip Chip flow

上芯片流程Flip Chip flow

Why do you need to underfill

填胶制程  Under-fill

1. 毛细作用型 Capillary type):

利用毛细力造成胶材之流动.

2. 异方向导电胶(Anisotropic conductive adhesive):

低温制程,分膏状(paste)和膜状(film)

3. 前置型(Pre-applied type):

小尺寸芯片(<6mm),点胶(Die attachment)后再回焊(Reflow)

制程与材料之限制:

1. 加强快速填胶与固化能力

2. 提升其界面之黏着力

3. 较低的吸水率

4. 提升低锡铅球间距内的流动性

5. 加强可重工性(rework)

Polymide passivation Evaporative solder bumping process

UBM:Cr/Cr-Cu/Cu/Au

编辑：黄飞