Pad Cratering

141 Pages·2011·6.39 MB·English

by  Nadia Anwar

Design for Excellence in the
Pb Free Era
ILTAM – December 5, 2011
Cheryl Tulkoff
Senior Member of the Technical Staff
[email protected]
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DfX Course Abstract
o Designing printed boards today is more difficult than ever before because of the increased lead free process
temperature requirements and associated changes required in manufacturing. Not only has the density of the
electronic assembly increased, but many changes are taking place throughout the entire supply chain
regarding the use of hazardous materials and the requirements for recycling. Much of the change is due to the
European Union (EU) Directives regarding these issues. The RoHSand REACH directives have caused many
suppliers to the industry to rethink their materials and processes. Thus, everyone designing or producing
electronics has been or will be affected.
o This course provides a comprehensive insight into the areas where design plays an important role in the
manufacturing process. This workshop addresses the increasingly sophisticated PCB fabrication technologies
and processes -covering issues such as laminate selection, micro/via and through hole formation, trace width
and spacing, and solder mask and finishes in relation to lead free materials and performance requirements.
Attendees will have a unique opportunity to obtain first-hand information on design issues that impact lead
free manufacturability.
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Instructor Biography
o Cheryl Tulkoff has over 22 years of experience in electronics manufacturing with an emphasis on
failure analysis and reliability. She has worked throughout the electronics manufacturing life cycle
beginning with semiconductor fabrication processes, into printed circuit board fabrication and
assembly, through functional and reliability testing, and culminating in the analysis and evaluation of
field returns. She has also managed no clean and RoHS-compliant conversion programs and has
developed and managed comprehensive reliability programs.
o Cheryl earned her Bachelor of Mechanical Engineering degree from Georgia Tech. She is a published
author, experienced public speaker and trainer and a Senior member of both ASQ and IEEE. She
holds leadership positions in the IEEE Central Texas Chapter, IEEE WIE (Women In Engineering), and
IEEE ASTR (Accelerated Stress Testing and Reliability) sections. She chaired the annual IEEE ASTR
workshop for four years and is also an ASQ Certified Reliability Engineer.
o She has a strong passion for pre-college STEM (Science, Technology, Engineering, and Math) outreach
and volunteers with several organizations that specialize in encouraging pre-college students to pursue
careers in these fields.
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Course Outline
MODULE 1: INTRODUCTIONS
MODULE 5: DESIGN FOR MANUFACTURABILTY
o Intro to Design for Excellence
o DfX& Physics of Failure Concepts
MODULE 6: PRINTED CIRCUIT BOARDS
MODULE 2: INDUSTRY STANDARD DESIGN RULES o Surface Finishes
& ENVIRONMENTAL LEGISLATION o Cracking & Delamination
o Overview of Industry Standard Organizations o Laminate Selection
o Examples: IPC, JEDEC, ISO o PTH Barrel Cracking
o Description of common standards in use
o CAF
o REACH, ROHS….
o Strain/Flexure Issues & Pad Cratering
MODULE 3: PHYSICS OF FAILURE o Cleanliness
o Electrochemical Migration
MODULE 4: COMPONENTS
o Selection MODULE 7: SOLDERS & SOLDERING
o Critical Components o Lead Free Solder Alloy Update
o Moisture Sensitivity Level o Copper Dissolution
o Temperature Sensitivity Level o Mixed Assembly
o ESD
o Plating Material
MODULE 8: SOURCING
o Misc
o Lifetime
o Derating& Uprating
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Agenda
o 08:45-09:00 Welcome
o 09:00-10:00 Introduction to Design for Excellence (DfX)
o 10:00-11:00 Industry Standards & Guidelines
o 11:00-11:15 Coffee Break
o 11:15-12:00 Environmental Regulations & Legislation
o 12:00-12:45 Physics of Failure
o 12:45-13:45 Lunch Break
o 13:45-14:30 Components
o 14:30-15:15 Printed Circuit Boards & Halogen Free
o 15:15-15:30 Refreshments
o 15:30-16:15 Solders & Soldering & Pb-Free
o 16:15-17:00 Sourcing Issues
o 17:00-17:15 Q&A
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Module 1: Introduction
Introduction to Design for Excellence (DfX)
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Introduction to Design for Excellence
manufacturing!
reliability!
environment!
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What is DfX?
o Primary definition: Methodology that involves various
groups with knowledge of different parts of the product
lifecycle advising the Design Engineering functions during
the design phase
o Alternative definition: Process of assessing issues beyond
the base functionality before physical prototype
Base Functionality: Meeting customer expectations of function,
o
cost, and size
Other Issues: Manufacturability, Reliability, Testability, Sourcing,
o
Environment
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Why These Issues Now?
o Manufacturability: Realization that quality control is not
sufficient by itself to minimize defect occurrence
o Testability: Inability to rely on physical access due to
increasing densities
o Sourcing: Contract manufacturing + automation + off-the-
shelf
o Reliability: As electronic technology reaches maturity,
there is less differentiation in price and performance with
a reduction in part margins
o Environment: Legislation (REACH, RoHS, etc.) and customer
awareness
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Design for Reliability (DfR) Defined
DfR: A process for ensuring the reliability of a product
o
or system during the design stage before physical
prototype
Reliability: The measure of a product’s ability to
o
…perform the specified function
o
…at the customer (with their use environment)
o
…over the desired lifetime
o
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Why Design for Excellence (DfX)?
The foundation of a reliable
o
product is a robust design
Provides margin
o
Mitigates risk
o
from defects
Satisfies the
o
customer
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Why DfX?
Architectural Design for Reliability, R. Cranwell and R. Hunter, Sandia Labs, 1997
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Why DfX? (cont.)
Reduce Costs by Improving
Reliability Upfront
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Who Controls Hardware Design?
Electrical Designer Mechanical Designer
o Component selection o PCB Layout
o Bill of materials (BOM) o Other aspects of
Approved vendor list (AVL) electronic packaging
o
Both parties play a critical role
in minimizing hardware
mistakes during new product
development
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When Do Mistakes Occur?
o Insufficient exchange of information between electrical
design and mechanical design
o Poor understanding of supplier limitations
o Customer expectations (reliability, lifetime, use
environment) are not incorporated into the new product
development (NPD) process
There can be many things that “you don’t
know you don’t know”
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Reality of Design for Reliability (DfX)
o Ensuring reliability of electronic
designs is becoming increasingly
difficult
Increasing complexity of electronic
o
circuits
Increasing power requirements
o
Introduction of new component and
o
material technologies
Introduction of less robust components
o
o Results in multiple potential drivers
for failure
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Reality (cont.)
o Predicting reliability is becoming problematic
Standard MTBF calculations can tend to be inaccurate
o
A physics-of-failure (PoF)
o
approach can be time-
intensive and not always
definitive (limited insight
into performance during
operating life)
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Process of DfX (example)
http://www.reliasoft.com/newsletter/v8i2/reliability.htm
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Limitations of Current DfX
o Too broad in focus (not electronics focused)
o Too much emphasis on techniques (e.g., FMEA and FTA) and not
answers
o FMEA/FTA rarely identify DfR issues because of limited focus on the
failure mechanism
o Overreliance on MTBF calculations and standardized product
testing
o Incorporation of HALT and failure analysis (HALT is test, not
DfR; failure analysis is too late)
o Frustration with ‘test-in reliability’, even HALT, has been part of the
recent focus on DfR
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DfR and Physics of Failure (PoF)
o Due to some of the limitations of classic DfR, there has
been an increasing interest in PoF (aka, Reliability Physics)
o PoF Definition: The use of science (physics, chemistry, etc.)
to capture an understanding of failure mechanisms and
evaluate useful life under actual operating conditions
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