Sherlock 4.0 and Printed Circuit Boards

Transcription

1 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

2 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

3 PCB Sherlock Virginia Manor Rd Ste 290, Beltsville MD

4 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

5 Printed Circuit Board Composite material Reinforcement (glass cloth) Polymer (resin) Copper Glass fibers polymer copper

6 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

7 Copper Thickness specified as a weight: Weight rolled out over a square foot, determines the thickness Thickness (mils) = Copper weight (oz) * oz copper = 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, µm During manufacturing of the copper layer starts out as complete and is etched away to define the interconnects

8 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

9 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)

10 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

11 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

12 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

13 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

14 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

15 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

16 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

17 Trace Modeling

18 Geometric Conversion of Traces

19 This is a de-featuring function that helps reduce the number of elements produced in the FEA tool Effect of Arc Length

20 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

21 Script Based Material properties assigned to copper and resin areas Best suited for generating detailed package models for investigating package CTE

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24 Additional Board Modeling Techniques Mosaic technique, material properties are averaged over the individual elements

25 PCB Meshing Techniques

26 Meshing Techniques Uniform model, homogeneous properties for the whole board Layered model, homogenous properties per layer (layers have different mechanical properties)

27 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

28 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

29 Lead Modeling (cont.) Sherlock automatically post processes the simulation results to extract the strains developed in the lead to make fatigue predictions for it

30 Lead Modeling

31 Lead Modeling (cont.) Sherlock automatically post-processes the FEA results to make predictions for lead vibration fatigue

32 Lead Modeling (cont.) Bonded model with leads on all through hole components, model exported into Abaqus or Ansys

33 Sherlock 4.0 allows the user to define parameterized heat sinks to the top of components Heat Sink Modeling

34 Heat Sinks

35 Effect of Heatsinks

36 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

37 Setting a Router Layer Sherlock will automatically detect the presence of a routing layer Can set manually

38 Once imported the cutouts are editable Routing Cutout

39 PCB with Cutouts

40 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

41 Questions?? Thank you! Nathan Blattau Tom O Connor toconnor@dfrsolutions.com 41