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Method for soft metal interconnects and sockets with metal features and/or Cu tapers for FCBGA or FCLGA package and MB assembly

IP.com Disclosure Number: IPCOM000029126D
Publication Date: 2004-Jun-16

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for soft metal interconnects and sockets with metal features and/or Cu tapers for flip-chip ball-grid array (FCBGA) or flip-chip land-grid array (FCLGA) package and motherboard (MB) assembly. Benefits include improved functionality, improved performance, improved environmental friendliness, improved ease of implementation, improved process simplification, and improved support for future technology.

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Method for soft metal interconnects and sockets with metal features and/or Cu tapers for FCBGA or FCLGA package and MB assembly

Disclosed is a method for soft metal interconnects and sockets with metal features and/or Cu tapers for flip-chip ball-grid array (FCBGA) or flip-chip land-grid array (FCLGA) package and motherboard (MB) assembly. Benefits include improved functionality, improved performance, improved environmental friendliness, improved ease of implementation, improved process simplification, and improved support for future technology.

Background

              A reliable low-resistance socket is required due to the extremely high current of future high-power CPUs. Without such a socket, self-heating and reliability issues are expected as the number of pins required are greater than the number than can be supplied.

              High resistance occurs in conventional sockets. High current through the sockets require low resistance to create low dissipation as expressed in the following equation:

Power = Current2 x Resistance

              Higher dissipation results in higher socket temperatures. The situation is expected to become critical due to higher performance and power requirements.

              The socket in a package-to-MB assembly provides the interconnection between the FCPGA package and the MB. A bolt joint, for example, apply adequate compressive pressure to assure robust electrical and thermal performance. The manufacturer typically uses an additional clamping mechanism or heatsink clips (see Figure 1).

              The problem of increased current through sockets is conventionally solved by increasing the number of pins (see Figure 2). The resistance of the conventional pin design is 1.65 mΩ.

Each pin provides power dissipation. However, this solution is expensive not only in terms of actual dollar cost for the extra pins but also for the chip surface area required for the extra pins. The number of pins added for power dissipation may not lower the resistance sufficiently more than the resistance of the pins in the core region. As a result, the effectiveness of the additional pins may not sufficiently reduce the current flowing through one region of the package. The additional pins must provide effective direct current (DC) shunting.

              As socket BGA joint pitch shrink, the mechanical/electrical design for sockets becomes very challenging and may limit central processing unit (CPU) performance.

              Indium (In) is a well-known soft solder. The indium solder ball/coating can be easily penetrated by sharp surfaces, while the conventional solder balls cannot be easily penetrated.

 


General description

              The disclosed method includes soft metal interconnects and a socket with metal features and/or Cu tapers for FCBGA and/or FCLGA package/socket/motherboard system assembly. The interconnects and socket provide better electrical contacts.

The key elements of the disclosed method are:

•             Soft metal layer, su...