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|Advanced Assembly Materials Development for Enabling Heterogeneous Integration and 3D Packaging|
|Keywords: SiP, Underfill, Molding|
|Mega trends like big data, artificial intelligence, 5G connectivity and autonomous driving applications are big drivers for advanced packaging of semiconductor devices. These trends spur growth in the infrastructure needed for data centers, servers, networking devices that store the data and growth in the connected devices in consumer electronics, automotive, industrial applications that create the data. Alongside these trends, the consumer electronics devices pack more functionality and performance in an increasingly smaller form factor for applications in mobile and handheld devices. In all these areas advanced packaging of semiconductor devices are enabling next generation devices for high bandwidth communication between the processors and memory devices. New technologies in advanced packaging are enabling miniaturization of semiconductor packages and heterogeneous integration of semiconductor chips to form a system in package (SiP) architecture. Advanced architectures for packaging and assembly come with a myriad of challenges that need innovation not just in the packaging design but also need innovative assembly materials in these devices. Requirements vary between end applications such as mobile, high performance computing and automotive components. There are some common challenges that are addressed by advanced packaging materials in all these applications. In this paper, we will present the pain points of various advanced packaging methods and an overview of the different material technologies for encapsulation, underfills, warpage control, electro- magnetic interference (EMI) shielding materials that enable these advanced packages. In high performance computing applications, 2.5D or 2.1D packaging technology is used to connect a processor and memory on an interposer layer. In this architecture, the dominant trends are package sizes greater than 65 mm x 65 mm, larger die sizes, minimal keep out zones (KoZ) between dies and low warpage of final package. So, assembly materials need to address these requirements for large package architectures. Assembly materials like capillary underfills need to be compatible with large die size, have fast flow properties to flow in thinner gaps with high density interconnects and maintain low KoZ. Encapsulation for these devices is done using liquid compression molding (LCM) materials, these materials need to have good adhesion to the various interfaces (Si, CUF, interposer material, etc.) in addition to having extremely low warpage after molding. 3D stacking of ICs is commonly used in high bandwidth memory devices which each generation device having higher I/O count and thinner die thickness (<50 um). Here, thermocompression bonding (TCB) technology is used for die stacking applications where a non- conductive film (NCF) is used as pre- applied wafer level underfill in the die stack. NCF materials have an exhaustive list of technical requirements for good interconnect formation during bonding, mainly no filler entrapment, no voiding, good reliability, low bond line thickness, and excellent cure kinetics. SiP applications for mobile and handheld devices also need a variety of materials to solve warpage challenges, KoZ requirements, EMI shielding, etc. Fan-out wafer level packaging (FOWLP) is predominantly used for packaging of application processors, and power management chips. Encapsulation processes requires a low warpage LCM material that can minimize the wafer-level warpage to under 500 um across a wafer.. When multiple components are placed close to each other in a SiP architecture, low KoZ underfills like pre-applied non-conductive paste (NCP), NCF or CUF is important for high density integration. Also, EMI shielding materials for conformal and compartmental shielding are required for EMI isolation in radio frequency SiP packages where certain elements of the package or the board require shielding from other radiating elements in the device. We will discuss the development of a sprayable material for conformal shielding and a jettable material for compartmental shielding application.|
|Ramachandran K. Trichur, Global Head of Advanced Packaging Market Segment
Irvine , CA