Fellow Designers;
Now that you have had an opportunity to review the objects for the Advanced
PWB Design Principles, it is time to send in your comments, and/or input to
the study guide. Attached is a full list of objectives for your reference.
As a reminder, we will be asking for comments by section. At this time,
comments for ONLY section 1, Layout, should be sent to Hugo Scaramuzza at
[log in to unmask]
When commenting, please identify the objective number, your concern and any
suggestions, for improvement. If you are sending input for the study guide,
please identify accordingly.
LAYOUT
1B.1 Apply design standards to meet manufacturing and assembly goals.
· Recognize manufacturing and assembly cost trade-offs
· Identify characteristics for robust assembly
· Illustrate check list for high first pass yields
· Demonstrate use of applicable standards
1B.2 Distinguish complete description of parts, quantities, manufacturers
code, and special ordering instructions from an engineering provided
material list.
· Describe the purpose of using standard components
· Describe the reason for having a complete parts list
· Describe the difference between standard/nonstandard parts
· Explain who and why the parts list needs approval
1B.3 Identify PCB panelization strategy compatible with the manufacturing
processes.
· Describe manufacturing allowances and tolerancing principles
· Explain how to calculate maximum board to panel size relationship
· Explain the need for a fabrication allowance on the panel
· Describe the cost trade-offs between various panel sizes
1B.4 Make a density evaluation.
· Identify the characteristics to use in a density analysis
· Explain why density evaluations are important
· Explain what constitutes a usable board area
· Explain what constitutes the component area
1B.5 Develop strategy for board type selection based on end product
performance.
· Define check list of properties to make board selection
· Explain the need for test considerations on the check list
· Identify the temperature ranges for end use environments
· Establish throw-away concepts related to cost of repair
1B.6 Develop standardization strategy for manufacturing and assembly goals.
· Explain the need to standardize board sizes through fabrication
· Explain the need to standardize board sizes through the assembly process
· Explain the need to control bow and twist
· Explain the need for bare board/assembly test
1B.7 Translate tooling requirements for individual board design.
· Define tooling output which aid fabrication processes
· Define tooling output which aid the assembly process
· Define tooling output which aids testing (bare board/assembly)
· Define the need for artwork overlays
1B.8 Organize layout by function, confine analog and digital circuitry to
desired areas, to minimize cross talk and simplify testing strategies.
· Explain importance of test personnel involved early in the layout cycle
· Explain the need for all node testing
· Describe cross talk between analog/and digital circuitry
· Explain power distribution for both analog and digital circuitry
1B.9 Develop strategy for blind and buried via technology.
· Explain the fabrication process for blind and buried via technology
· Describe the difference between blind and buried vias
· Explain the cost difference between blind, buried and through hole
technology
· Explain hole size differences for blind, buried and through hole processes
ELECTRICAL CONSIDERATIONS
2B.1 Characterize electrical clearance for coated and uncoated boards and
assemblies, at various altitudes using the IPC electrical spacing
table.
· Define surface and internal electrical clearance conditions
· Define differences and similarities between conductor and part clearances
· Define conditions for moisture that impact spacing requirements
· Determine differences between conformal coating and soldermask
2B.2 Interpret conductor thickness requirements for various currents with
minimum temperature rise using the standard current carrying capacity
chart.
· Define the derating factor for double sided and multilayer boards
· Define the lowest temperature rise for a particular conductor
· Define the requirements for power supply boards
· Define methods for cooling circuitry as opposed to components
2B.3 Formalize preferred power and ground routing techniques.
· Identify DC power return and AC reference plane
· Define a power structure with proper decoupling techniques
· Determine correct decoupling values for a specific circuit
· Define power distribution paths that link power supply and devices
receiving power
2B.4 Differentiate physical layout requirements for digital and analog (A/D)
circuits.
· Explain the difference between analog and digital circuitry
· Explain "state information"
· Explain "wave form characteristics"
· Explain the physical layout for power distribution for A/D circuits
2B.5 Identify schematic correctness for capacitance polarity requirements or
need for pull-down resistors.
· Define methods for checking (check list) electronic diagrams
· Develop a designers user guide for capacitance/resistor/diode usage
· Establish component part to schematic symbol relationship (polarize)
· Identify feed back loops in the schematic or logic diagram
2B.6 Generalize op-amp placement and routing techniques.
· Develop placement guidelines for a single op-amp
· Develop placement guideline for quad op-amp
· Analyze conductor routing strategies for an op-amp
· Identify why routing around an op-amp is important
MATERIAL PROPERTIES
3B.1 Determine proper metallic plating characteristics.
· Identify metallic platings for fabrication that stay with the board
· Define the primary functions of metallic coatings
· Describe platings used in the process as an etchant resist
· Define those platings that are impervious to the environment
3B.2 Categorize materials based on end use environment.
· Derive materials list capable of low CTE properties
· Specify reinforcements that restrict X & Y axis movement
· Define materials that have good thermal properties
· Determine methods of cooling or heat transfer in various conditions
3B.3 Explain various board material and their properties.
· Explain the difference between epoxy and high temperature laminate
· Explain the difference between laminate and prepreg
· Explain the difference between epoxy and high temperature prepreg
· Explain documentation requirement details for material callout
3B.4 Categorize coatings based on end use environment and assembly
technology.
· Define the limitation/applications of metallic/nonmetallic coatings
· Determine the use of coatings that can be easily removed for repair
· Specify coating requirements for high humidity applications
· Compare silicon, epoxy, polyurethane, acrylic, paraxylene coatings
3B.5 Determine the minimum dielectric spacing between conductive layers.
· Propose minimum dielectric separation for PCMCIA cards
· Design and formalize a standard board family construction
· Establish the test requirements for using a single ply core material
· Develop auditing procedures that validate thin dielectric separation
COMPONENT REQUIREMENTS
4B.1 Determine strategy for mounting different package types.
· Identify case sensitive component packages
· Describe component packages requiring thermal management
· Define the need and use of polarized components
· Define analysis necessary to evaluate special mounting
4B.2 Illustrate the impact of card edge fingers.
· Define spacing requirements between contact fingers
· Describe conductor routing restrictions
· Define contact finger plating requirements
· Describe contact finger electrical requirements
4B.3 Explain the significance of connector uniformity in a multi-connector
system.
· Define the cost impact of using dissimilar connectors
· Relate time factors involved in choosing and verifying connectors
· Propose solution for selection of non available connectors
· Define availability and cost differential of various connector types
4B.4 Develop procedure for specifying clinched leads.
· Describe cost considerations on assembly
· Determine impact of spacing requirements when using clinched leads
· Describe documentation method for specifying clinched leads
· Define factors involved in using clinched leads
4B.5 Recognize when board stiffeners are required.
· Define the board size that make use of stiffeners mandatory
· Describe the various types of materials used to make a stiffener
· Define shock and vibration benefit afforded by adding a stiffener
· Define when to use fiber or plastic stiffeners
ASSEMBLY TECHNOLOGY
5B.1 Develop an implementation strategy for assembly.
· Describe sequence that components should be placed on the board
· Describe factors used in a pick and place file
· Define ways to lower the cost of the assembly operation
· Define tolerance conditions for smooth assembly processing
·
5B.2 Determine component orientation based on assembly panel configuration.
· Define I/C orientation intended to see wave solder exposure
· Describe passive chip orientation for wave soldering
· Indicate component arrangement preference to reduce cycle time
· Define orientation relationship to facilitate pick and place through-put
5B.3 Describe equipment specifications for semi and fully automatic
insertion.
· Determine maximum board size requirements
· Define insertion head clearances
· Describe the purpose of the anvil and clearances necessary
· Define minimum component to component spacing
5B.4 Transfer the assembly strategy to physical board design.
· Define methods to assess application of assembly strategies
· Identify the benefits of standardized component orientation
· Describe a placement strategy to reduce assembly cost
· Define when components require hand soldering (non-machine)
5B.5 Describe Shock and Vibrations requirements in component mounting.
· Define specific mounting approaches to reduce impact of S&V
· Describe or determine end-use environments
· Develop fixed or replaceable mounting techniques
· Determine classification of reliability development test procedures
5B.6 Calculate board size limitations for specific assembly equipment.
· Describe method to determine assembly equipment capability
· Recommend panelization for board assembly
· Define the principles used for standardization at an assembly facility
· Develop strategy for assembling small boards (eg.25x25 mm)
BOARD FABRICATION
6B.1 Develop panelization requirements for board/board array breakaway.
· Recommend routing widths between images
· Describe scoring techniques referred to as "V" groove
· Select breakaway style and number of "tabs" required
· Describe thieving requirements in breakaway areas
6B.2 Calculate board size limitation for specific fabrication equipment.
· Recognize how panel shape affects cost
· Develop a strategy for maximum material usage on a panel
· Differentiate fabrication and assembly panel border requirements
· Determine optimum spacing of boards for assembly and test
6B.3 Examine process allowances for conductor traces.
· Describe the relationship between plating and etching
· Determine an unacceptable undercut condition on conductors
· Assess characteristics of four ounce copper on a .2mm conductor
· Describe the differences between panel and pattern plating
6B.4 Relate plating processes, elements used and cost to performance
issues.
· Describe cost impact of using SMOBC
· Define the process used to apply Solder Mask Over Bare Copper
· Describe the etching process for subtractive and semi-additive
· Describe the tin-lead plating process and thickness capability
6B.5 Apply hole aspect ratio classification.
· Describe how aspect ratio of plated-through holes affects producibility
· Describe a low producibility board based on hole to thickness
· Delineate the difference between 1:3 vs 1:9 aspect ratios
· Determine sufficient plating requirements under various conditions
PHYSICAL BOARD REQUIREMENTS
7B.1 Describe the criticality of the board length to width relationship.
· Define how to prevent bow and twist
· Define different characteristics of etching and tolerances
· Define the difference between dimensional stability or consistency
· Describe the effects on test equipment
7B.2 Define the effects of copper balance on the fabrication process.
· Explain the need for copper balance for uniform plating characteristics
· Explain the relationship of copper balance to bow and twist
· Describe correction techniques for unbalanced constructions
· Develop a strategy for internal copper plane balancing
7B.3 Apply thermal management techniques for boards.
· Define using heat sinking planes and thermal vias
· Describe system methods to remove heat from planes
· Describe methods for board "hot spot" determination
· Define board fabrication materials used for heat sinking
7B.4 Apply thermal management techniques for components.
· Identify power components and methods of heat removal
· Describe a thermal dissipation map and when it is required
· Define the major types of heat transfer techniques
· Describe thermal conduction techniques and board characteristics
7B.5 Determine the requirements which affect the physical parameters of the
boards.
· Define the relationship of component count and conductor density
· Describe mechanical restrictions that determine board size
· Relate component and circuit density to layer count
· Detail the manufacturing steps and their optimization to reduce cost
7B.6 Identify physical and electrical properties that impact structural
strength.
· Define board thicknesses for various structural support applications
· Describe pros and cons of thick planes used to enhance strength
· Define balanced circuitry and impact on bow and twist
· Define electrical parameters affected by asymmetrical constructions
DOCUMENTATION
8B.1 Develop board level documentation requirements.
· Define the documentation package for full reprocurement
· Describe how phototool or circuit configuration is referenced
· Define the thickness and detailed board construction requirements
· Develop techniques to use hole description as acceptance criteria
8B.2 Specify the requirements for the master drawing of a double sided or
multilayer rigid board.
· Establish dimensioning scheme for a double-sided board
· Define proper viewing criteria for layer stack-up
· Describe proper note set for double-sided and multilayer boards
· Define construction techniques and over-all thickness conditions
8B.3 Define minimum requirements for electronic description artwork
masters.
· Define how circuit features of a board are described electronically
· Relate the method of providing tolerances on conductors
· Describe electrical continuity for board circuitry
· Define viewing conventions for conductive non-conductive layers
8B.4 Analyze tolerancing on a board level.
· Define the tolerances needed to identify keying slot locations
· Describe tolerance conditions for mounting a DIP on a metric grid
· Describe different methods used to locate circuitry
· Describe how bilateral dimensioning affects coordinate location
8B.5 Define the methodology to obtain non-standard part information.
· Define completeness required for specification control drawing
· Detail methods for interpretation of a vendor specification sheet
· Describe how missing part dimensions may be derived
· Define importance of multiple sources for part selection
8B.6 Analyze board level tolerance conditions related to mounting
enclosure.
· Define the mounting clearance relationship in a card-guide system
· Describe back plane connector mating tolerances for plug-in boards
· Define the necessary clearance for board installation or removal
· Define most liberal board periphery and enclosure dimensioning
TESTING TECHNOLOGY
9B.1 Identify strategies for assembly test implementation.
· Identify requirements for bare board testing
· Define component placement as it impacts testing
· Identify differences between in-circuit and functional testing
· Describe when test points are needed at passive components
9B.2 Propose probe point physical land pattern characteristics for most
efficient test fixture performance.
· Describe minimum land size for single side test access
· Define differences between round vs square lands
· Define top side and bottom side land configuration
· Distinguish benefits of using test points as opposed to test vias
9B.3 Identify what is done to differentiate between a circuit feature vs. a
test point.
· Define when to use vias as test points
· Identify the use of fiducials in determining test point location
· Relate how to locate a test point feature
· Detail how a conductor may be used as a test point
9B.4 Identify parameters for in-process test for use of in-process test
coupons.
· Define drilling registration coupon evaluations
· Detail plating thickness coupon evaluations
· Relate electrical test coupons
· Establish plated through-hole integrity coupon techniques
RELIABILITY
10B.1 Identify tools and techniques used to obtain traceability of quality.
· Define the use of SPC in establishing quality assurance
· Describe the need for in-process test coupons
· Define the use of controlled experimentation as a quality tool
· Define systems used for lot to lot or part quality traceability
10B.2 List criteria for reliability of boards subject to shock and vibration
in normal service.
· Describe bare board parameters impacted by shock or vibration
· Define test methodology used to characterize product reliability
· Explain Assembly "weak links" when subjected to vibration or shock
· Detail methods used to neutralize impact on board or assemblies
10B.3 Identify reliability issues of plated-through holes.
· Identify via characteristics
· Define barrel characteristics and weaknesses
· Detail issues on post separation
· Determine testing conditions to establish reliability characteristics
10B.4 Identify solder connection reliability issues.
· Detail solder joint formation
· Explain substrate CTE mismatch related to components
· Define cyclic strain on solder joints
· Determine required solder volume to establish joint reliability
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