DRAM Modules

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Advantages:
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Highest Density
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Standard Modules available
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Disadvantages
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High cost
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Reliability Unknown
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Test and repair
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Board spacing requirements
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DRAM ZIP's

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Advantages
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High density
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Standard soldering technology
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Good Availability
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Disadvantages
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Board Spacing
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Special auto insert equipment
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Lead capacitance.
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Why Use Surface Mount?

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More IC's per square inch
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Higher performance
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Lower Cost
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Higher reliability because of automation
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SMT Council Objectives

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Leverage development effort
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Leverage quality improvement
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Accommodate over seas manufacturing
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Use SMT as a vehicle to transform manufacturing
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Transforming Manufacturing

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Reduce number of vendors and parts
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Improve quality control
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Efficiently use manufacturing facilities
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Reduce manufacturing cost
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Better link between design and test tools
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Standardize manufacturing
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SMT Design Strategy

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Be a surface mount user
(Do not work on developing the process)
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Continue to push for process compatibility
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Work closely with an SMT manufacturing division
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Design review layout
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Help specify new parts
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Develop footprints/design rules for new parts
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Proto-typing
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Concerns

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Standard PC layout to placement machine interface
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PC layout systems being SMT compatible
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Documented design rules and guidelines
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Incoming test / Board test
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Limiting number of part numbers - cost models
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Standard Panel Sizes
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Future Directions

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Double sided SMT
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TAB support
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Do NOT mix auto-insert through hole parts
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Continue to support through hole parts
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Why was SMT used on Firefox?

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Required memory would not fit on given board
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Manufacturing was receptive of SMT
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Modules - High cost and availability risks
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ZIP's - Availability and manufacturing problems
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Allows density to be doubled when double sided SMT available
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Design Challenges

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Definition and implementation of VLSI controller
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Establishing SMT design rules
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Providing monotonic control signals
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Delay line design
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High Speed SRAM's

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Modules - Cost, Availability, modeling
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ZIP's - Availability, lead capacitance
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SMT - SOJ will be a standard package for 16K x 4
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