What Can Lasers Do in System Level Packaging of Semiconductor?

 

 

 

What is system level packaging for integrated circuits?
What are the advantages of system level packaged chips and what are their uses?
What can lasers do in system level packaging?
This article elaborates on the application of lasers in integrated circuit system level packaging through text, images, application cases, and video clips.

 

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01  What is System Level Packaging (SiP)?

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1) Traditional Three-Level Packaging

Within an electronic products, such as desktop computers,

1st Level Packaging - is the process of packaging a single die into a single chip, such as a CPU, memory, etc;

2nd Level Packaging -  These packaged chips are inserted onto PCB to form specific functional boards, such as memory modules, display driver cards, etc;

3rd Level Packaging - is the process of inserting these single functional boards onto the motherboard, adding a casing to form a complete functional system.

 

Figure 1: 3 level packaging of electronic products

2) System level packaging (SiP)

With the development of packaging and testing technology, a single package can accommodate multiple bare dies, allowing a single chip to form a complete system. This packaging method is called System in Package.
 

Figure 2:  Apple Watch S1 chip, which integrates chips from different suppliers, constitutes all basic computer functions including CPU, memory, display driver, and also includes communication functions such as Wi Fi, Bluetooth, NFC, FM, etc. (Source: Electronics World News, September 22, 2015)

System level packaging has the following advantages:

• High packaging density, low internal parasitic capacitance and inductance, suitable for high frequency operation, low power consumption, allowing mobile terminal devices to have longer standby time.
• When developing new products, various functional standard chips available in large quantities can be selected to flexibly integrate new products, shorten development cycles, and reduce product development and bulk supply costs.

 

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02  LaserApplications in SiP

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1)  CPS Electromagnetic Shielding

As shown in Figure 2, the SiP module integrates RF circuits such as WiFi, Bluetooth, NFC, etc.  These RF devices cause interference to peripheral passive components such as CPUs, memory, and display drivers, and must be shielded.  The traditional approach is to package these RF devices separately, shield them with a metal cover, or shield them with vacuum sputtering or silver paste spraying.

 

Figure 3: Metal cover shielding increases packaging volume

 

Figure 4:  Sputtering overall shielding, unable to simultaneously implant passive components and RF devices inside the packaging body.

 

In order to package both RF devices and passive components into a single SiP module, it is necessary to partition the two types of devices, and then find a way to set up isolation metal walls. The currently effective process is to open grooves on the packaging body along the preset isolation line after packaging, inject silver paste into the grooves, and then apply silver spray or sputtering tp make metal shielding layer, as shown in Figure 5.
 

Figure 5: Compartment Shielding Process

开沟槽的较佳手段是激光，其优点是沟槽窄(窄至100um) 节省面积，位置精度高(10um) ，深度可控制到基板上预设的屏新线表面。

 

 

图6: 高通5G基带芯片采用局部隔仓屏蔽，将被动元件保护起来。

图7展示SCM-300型激光开槽机在生产中所开沟槽的实测几何构型

 

 

图7: SCM-300所开沟槽的三维测绘，符合芯片设计要求

视频短片: SCM-300型激光开槽机生产高通5G基带芯片，开槽位置精度s10um，沟槽尺寸精度S+3um。

 

 

2)立体封装中的激光钻孔
为进一步提高封装密度而采用立体封装，方法有双面封装(2.5D)和单面堆叠封装(POP)。

下图展示多层堆叠封装的工艺制程，激光钻孔用于层间信号连接。

 

 

图8: POP立体封装制程

双面封装中，芯片基板上预留的/0触点位置被塑封体覆盖了，因而无法用传统方法制作/0触点。激光钻孔工艺用来打开封/0悍盘上方的封装体，再置入锡球，锡欧融后形成略高于封装体表面的I/O触点阵列。下图示意双面封装中I/0触点制作的工艺流程。

 

 

图9：双面封装SiP模组的I/O触点制作流程

Dialog司为移动终端设备设计的一款电源管理露采用了双面封装技术，点尺寸235微米，触点pitch 300微米，300多个点，要求孔的位置精度<+10um;触点共面性要求钻孔的尺寸精度<+3um。

 

 

图10: SCM-322型TMV钻孔机孔型尺寸精度测量

 

 

图11: SCM-322型TMV钻孔机钻孔位号精度，10.9环!

视频短片: SCM-322型TMV激光钻孔设备生产双面封装电源管理器模组

 

 

 

3)板级封装芯片的激光分切
5iP芯片多用干移动终端设备，由于紧性要求，它的外形通常需要契合产品的外壳形状，因而不是规则的矩形，比如指纹辨识片、miniSD卡、SIM卡等，无法用轮刀进行分切。而激光刻切割出任何你需要的形状。
视频短片：SCM-320型激光分切机，多料夹自动上料，同轴视觉定位，分切后A0视觉检测，不良品自动分拣，JEDEC料盘自动收料，满料料盘自动码垛。

 

 

4)光局部分切
激光分切成本高效率低，而有些产品的边缘大部分是直线，只有局部是异形或曲线，可以先用激光切异形和曲线分，再用轮刀切直线部分，以提高效率峰低成本。

 

 

图12: 用激光和轮刀分别切割miniSD卡

视频短片:LCM系列基板激光微加工系统切割miniSD卡，多料夹自动上下料，多激光站并行生产，同轴视觉定位，定位精度+20um，A0)视觉检测，不良品自动分拣。

 

 

本次的介绍就到此为止了!