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Browse Prior Art Database

Defensive Publication for A Low Cost Thermal Ball Grid Array Package (LCTBGA)

IP.com Disclosure Number: IPCOM000008765D
Original Publication Date: 2002-Jul-10
Included in the Prior Art Database: 2002-Jul-10
Document File: 4 page(s) / 188K

Publishing Venue

Motorola

Related People

Mark Gerber: INVENTOR [+3]

Abstract

Currently there is a large price difference for high pin count packaging solutions that can dissipate 2.5 to 3 watts of power in a closed environment that allows for a temperature difference of 50C. The two most common solutions, targeted for this thermal performance range, include the Thermally Enhanced Plastic Ball Grid Array (TEPBGA) and the Tape Ball Grid Array (TBGA), which often can have a cost difference of 100% or more. This cost gap in combination with a number of other issues with these solutions have led to several investigations of alternative low cost thermal packaging solutions within Motorola. This defensive publication will discuss one such solution and the method for assembly that has been shown to be considerably less expensive than current open market solutions and is relatively easily integrated into a standard plastic ball grid array assembly process. Further perceived benefits of this packaging solution include improved MSL performance and lower package profile.

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Defensive Publication for A Low Cost Thermal

Ball Grid Array Package (LCTBGA)

Mark Gerber, Trent Thompson, Bennett Joiner

Abstract:

   Currently there is a large price difference for high pin count packaging solutions that can dissipate 2.5 to 3 watts of power in a closed environment that allows for a temperature difference of 50C.  The two most common solutions, targeted for this thermal performance range, include the Thermally Enhanced Plastic Ball Grid Array (TEPBGA) and the Tape Ball Grid Array (TBGA), which often can have a cost difference of 100% or more.  This cost gap in combination with a number of other issues with these solutions have led to several investigations of alternative low cost thermal packaging solutions within Motorola.  This defensive publication will discuss one such solution and the method for assembly that has been shown to be considerably less expensive than current open market solutions and is relatively easily integrated into a standard plastic ball grid array assembly process. Further perceived benefits of this packaging solution include improved MSL performance and lower package profile.

 Introduction:

   To develop an alternative low cost thermal packaging solution, the application and environment had to be understood.  In many cases, thermal packages are selected based on their junction-to-ambient thermal resistance values.  Alternatively, if the device will be operating in a natural convection environment, the packaging solution may rely more on conductive properties of the system board for thermal dissipation.  The total package thermal resistance, Theta-JA (junction to ambient) is usually some combination of both convective and conductive (Theta-JB- Junction-to-Board) environments.  This low cost thermal BGA solution that was developed has shown a significant benefit in both areas but the greatest benefit was seen in the conductive environment where the junction-to-board thermal resistance is the dominant thermal resistance. 

   Standard BGA devices usually are assembled with an organic substrate with two interconnect layers, a semiconductor chip, solder balls, gold wire and a encapsulation (liquid or molded). Most common types of low cost BGA include the OMPAC-Over Molded Plastic Array Carrier BGA and the Molded Array Plastic BGA (See Figure 1).

       Over-Molded Plastic Array Carrier-BGA                              Molded Array Plastic-BGA

                                                                                                       Figure 1

These packages are some of the lowest cost array packages on the market today but are limited in their thermal dissipation capabilities.  To improve the thermal aspects of this type of packaging solution, two extra substrate layers and thermal vias can be added to help better conduct the heat from the die and better dissipate it across the entire package.  This is commonly called a Thermally Enhanced Plastic Ball Grid Array (TEPBGA). 

   The Low Cost Thermal Ball Grid Array package builds on the MAPBGA packaging design by allowing for an improved thermal connection between the silicon die the heat source, and the mai...