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Low Cost Array Package and Method of Formation

IP.com Disclosure Number: IPCOM000011602D
Original Publication Date: 2003-Mar-07
Included in the Prior Art Database: 2003-Mar-07
Document File: 5 page(s) / 266K

Publishing Venue

Motorola

Related People

Mark Gerber: AUTHOR [+3]

Abstract

Pricing pressures in IC assembly have forced companies, like Motorola, to investigate alternative array packaging solutions over current standard array packaging options such as the Plastic Ball Grid Array (PBGA). Limitations on leadframe based packages, such as total I/O count & package body size, have often steered new IC’s to be packaged in a BGA type packaging solution. The primary disadvantages of organic BGA packaging solutions, when compared to leadframe-based packages, include: higher I/O inductance, poorer thermal performance and usually higher cost. In an effort to provide an alternative array packaging solution that addresses each of these disadvantages, Motorola has developed a new array packaging solution that utilizes existing Mold Array Package (MAP) assembly equipment that enables a leadframe based array packaging solution. This publication will discuss the perceived benefits, concept overview, design options and the assembly flow methodology.

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Low Cost Array Package and Method of Formation

Mark Gerber, Steve Safai, Dae Hong

January 29, 2003

Abstract:

   Pricing pressures in IC assembly have forced companies, like Motorola, to investigate alternative array packaging solutions over current standard array packaging options such as the Plastic Ball Grid Array (PBGA).  Limitations on leadframe based packages, such as total I/O count & package body size, have often steered new IC’s to be packaged in a BGA type packaging solution.  The primary disadvantages of organic BGA packaging solutions, when compared to leadframe-based packages, include: higher I/O inductance, poorer thermal performance and usually higher cost.  In an effort to provide an alternative array packaging solution that addresses each of these disadvantages, Motorola has developed a new array packaging solution that utilizes existing Mold Array Package (MAP) assembly equipment that enables a leadframe based array packaging solution.  This publication will discuss the perceived benefits, concept overview, design options and the assembly flow methodology.

Introduction:

   To develop an alternative low cost array packaging solution that is compatible with current MAP equipment, the standard MAP strip design must be understood.  Figure 1 shows an example of an organic MAP substrate strip.

                                                            Figure 1: Molded Array Substrate Strip Example

This strip design utilizes a transfer mold process to encapsulate a large portion of the BGA unit array (hatched area).  Once this strip is molded, it can then be marked and singulated by a saw singulation process.  This method of assembly allows for a high substrate strip utilization that ultimately reduces total unit cost.

     The low cost array package (LCAP) will utilize a leadframe strip design that is similar to the MAP strip design but the leadframe is made from a leadframe alloy and will incorporate a grid pattern in the leadframe design for die positioning and 2nd wirebond attach (see figure 2).

                                                                                Figure 2: LCAP Leadframe Strip Design

    The units that would be assembled within this strip design are shown below in two size examples (figure 3).  The first unit examples shows a 10x10 contact matrix with square pads located at 0.5mm pitch with a dummy die approx 1.6x1.5mm.  The second example shows a 8x8 contact matrix with pads located at 0.5mm pitch and a dummy die size approximately 2x2mm square.  These solutions allow the end user to wirebond to the outer 2-3 rows of contact pads providing a partial-array packaging solution.

                                                                                Figure 3: LCAP Unit Examples

    Figure 4 shows the assembly process build-up of this packaging solution and what the final packaged unit would look like.  In this pictoral example, an SMD (Surface Mou...