Sherlock 4.0 and Printed Circuit Boards DfR Solutions January 22, 2015 Presented by: Dr. Nathan Blattau Senior Vice President 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com
Who is DfR Solutions? The Industry Leader in Quality-Reliability- Durability of Electronics Fastest Growing Companies in the Electronics Industry - Inc Magazine Best Design Verification Tool - Printed Circuit Design 2012 Global Technology Award Winner
PCB Sherlock 4.0 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com
Printed Circuit Boards (PCB), also known as Printed Wiring Boards (PWB) Circuit Cards, etc.. Provides mechanical support and electrical interconnects to the electronic components Basic Materials Conductors Dielectric or insulator Structural reinforcement Woven glass cloth Fibers Must be able to provide the necessary: Electrical performance Structural performance Survive manufacturing
Printed Circuit Board Composite material Reinforcement (glass cloth) Polymer (resin) Copper Glass fibers polymer copper
Glass Style PCB laminates (and prepregs) are fabricated with a variety of glass styles Problem: All datasheet properties are for laminate with 7628 glass style Most laminate (and prepreg) in complex PCBs have a low volume fraction of glass (i.e., 1080 or 106) Glass Style Resin Volume Content Fiber Volume Content 1027 0.86 0.14 1037 0.86 0.14 106 0.84 0.16 1067 0.84 0.16 1035 0.83 0.17 1078 0.82 0.18 1080 0.79 0.21 2313 0.74 0.26 2116 0.71 0.29 3313 0.71 0.29 3070 0.68 0.32 1647 0.66 0.34 1651 0.66 0.34 2165 0.66 0.34 2157 0.66 0.34 7628 0.64 0.36
Copper Thickness specified as a weight: Weight rolled out over a square foot, determines the thickness Thickness (mils) = Copper weight (oz) * 1.37 0.5 oz copper = 0.685 mils, 17.4 µm 1 oz copper = 1.37 mils, 34.8 µm 2 oz copper = 2.74 mils, 69.6 µm 3 oz copper = 4.11 mils, 104.4 µm During manufacturing of the copper layer starts out as complete and is etched away to define the interconnects
Two types of resins (not including composition) are used: Pre-preg partially cured resin that flows and fills in all the etched away copper features, cures during the pressing process, does not have copper on it Laminate fully cured resin that typically has copper foil already attached to it There are many different types of resin systems Dicy Phenolic, etc.. Resin
PCB Materials and Reliability Historically, two material properties of concern Out-of-plane coefficient of thermal expansion (CTEz) Out-of-plane elastic modulus ( stiffness )(Ez) These drive fatigue of the plated through holes Key Assumption: No exposure to temperatures above the glass transition temperature (Tg) (field environment) The two material properties (CTE and E) are driven by choices in resin, glass style, and filler Additional concern is in-plane properties (solder joint fatigue)
Printed Circuit Board Properties The CTE mismatch between the printed circuit board and the components attached to it is one of the major fatigue issues of electronics Warpage and movement of the PCB during reflow can cause cracked components, starved solder joint and other assembly related defects 10
Coefficient of Thermal Expansion Is the amount a material expands when exposed to a change in temperature It is unlikely that the designer or end user will be able to influence the component properties Component packaging is typically driven by the die and assembly Passing of JEDEC level package tests May be able to pick parts with different lead frame materials Printed wiring board properties Designer can influence printed wiring board properties Glass style Laminate type Copper Thickness This is one of the main factors that drive solder joint fatigue CTE mismatch within the printed circuit board causes warpage of the board during thermal exposure
Influence of Board Properties In the past most electronic packages had CTE values closer to that of copper, 17.6 ppm/ C Larger die and smaller packages have driven a reduction in the component CTE, examples: Leadless ceramic chip resistors 5.6 ppm/ C QFN (quad flat no-leads) 8 to 12 ppm/ C The CTE of the laminates has decreased over the years The PCB laminate manufactures do not make it easy to determine the CTE of their laminate
Solder Joint Fatigue Elimination of leaded devices Provides lower RC and higher package densities Reduces compliance Cycles to failure -40 to 125C QFP: >10,000 BGA: 3,000 to 8,000 CSP / Flip Chip: <1,000 QFN: 1,000 to 3,000
Not only a PCB issue but also a major concern of laminate based components BGA devices LGA device Board Warpage As the solder joints get smaller the more sensitive they are to component and board warpage effects QFN solder joints are more susceptible to dimensional changes 14
Adds additional tools for more detailed modeling of the printed circuit board and components Detailed FEA modeling options for traces Export of PCB traces to FEA tools Heatsink Modeling Sherlock 4.0 Additional lead modeling capabilities Improved ODB++ parsing, improved cut out editor and the ability to use routing files
More FEA Model Parameters Allows more flexible FEA model generation Options for node and element numbering Vertical meshing size Element types 1 st order 2 nd order 3D solid shell
Trace Modeling
Geometric Conversion of Traces
This is a de-featuring function that helps reduce the number of elements produced in the FEA tool Effect of Arc Length
Sherlock generates scripts that build the PCB in FEA Tools (.apdl or.py supported) Assigns material properties to the regions Can export copper, resin or drill features Designed for doing more detailed analyses of substrates using finite element simulations Models can be used for doing warpage analyses Thermal conduction simulations, etc.. These models are typically too detailed for use in mechanical shock or vibration simulations Trace Export
Script Based Material properties assigned to copper and resin areas Best suited for generating detailed package models for investigating package CTE
Additional Board Modeling Techniques Mosaic technique, material properties are averaged over the individual elements
PCB Meshing Techniques
Meshing Techniques Uniform model, homogeneous properties for the whole board Layered model, homogenous properties per layer (layers have different mechanical properties)
Meshing Techniques, cont Uniform elements model, mechanical properties vary only in-plane Layered elements model, each element has properties computed based on location and layer
Lead Modeling Sherlock now allows one to add through hole or surface mount leads to select components As expected adding features greatly increases the FEA model complexity 3D part viewer shows the part
Lead Modeling (cont.) Sherlock automatically post processes the simulation results to extract the strains developed in the lead to make fatigue predictions for it
Lead Modeling
Lead Modeling (cont.) Sherlock automatically post-processes the FEA results to make predictions for lead vibration fatigue
Lead Modeling (cont.) Bonded model with leads on all through hole components, model exported into Abaqus or Ansys
Sherlock 4.0 allows the user to define parameterized heat sinks to the top of components Heat Sink Modeling
Heat Sinks
Effect of Heatsinks
Improved Cut Out Operations Allows the user to specify routing files for making cuts in the circuit board Polygon are now supported for making complex cut shapes manually Predefined Shapes Slots Circular Rectangular
Setting a Router Layer Sherlock will automatically detect the presence of a routing layer Can set manually
Once imported the cutouts are editable Routing Cutout
PCB with Cutouts
This Sherlock release is focused on adding additional tools to allow more detailed Finite Element Modeling of circuit board assemblies and packages Geometric trace modeling Improved cutouts Lead structures Heatsinks Sherlock 4.0
Questions?? Thank you! Nathan Blattau 1-301-640-5821 nblattau@dfrsolutions.com Tom O Connor 301-640-5812 toconnor@dfrsolutions.com 41