DEDICATED TO EMBEDDED SOLUTIONS

DEDICATED TO EMBEDDED SOLUTIONS

RELIABILITY IN SUBSEA ELECTRONICS TECHNIQUES TO OBTAIN HIGH RELIABILITY

STIG-HELGE LARSEN KARSTEN KLEPPE DATA RESPONS 2012-10-16

AGENDA

Introduction

Analysis and Design Techniques

Reliability Predictions

FRACAS and Data Processing Techniques

Production and Repair

Testing

Reliability Program Planning

2

THIS IS DATA RESPONS

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CUSTOMISATION

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Humidity

Altitude

Temperature

Vibration

Salt spray

Shock

EMC

Physical size

Interfaces

Functionality

Performance

Power demands

Regulations

Standards

Operating systems

Software architecture

Hardware platform

Processor architecture

Memory and storage

Communication & I/O

Display and touch

EXTREME

CONDITIONS

CHOICE OF

TECHNOLOGY

CUSTOM

SPECIFICATION

EXAMPLE: CURRENT SENSOR BOARD

Meassuring range: 0.2–1.2 A AC

Accuracy: Better than ± 1.0 %

CAN bus interface

4-20 mA outputs

Qualified according to ISO 13628-6 for Subsea Production Control Systems

Based on Hall effect current sensor

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RELIABILITY IN SUBSEA ELECTRONICS

INTRODUCTION

Reliability in Data Respons

Reliability study

IEC 61508

QA system

Reliability

The ability of an item to perform a required function under stated conditions for a specified period of time

Availability

The proportion of time for which the equipment is able to perform its function

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SUBSEA

Characteristics

Relative low volumes

Need for high reliability

Low accessibility

High cost in case replacements

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KEY POINTS

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Techniques to obtain high reliability in electronics

Topic Areas:

Relevant Themes:

Key Points: Design Techniques and Analysis

Root Causes of Failures

Failure Reporting and Corrective Actions System

Automated Testing

Accelerated Stress Testing

Reliability Program Plan

ANALYSIS AND DESIGN TECHNIQUES

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Topic Areas:

Relevant Themes:

Key Points: Analysis and Design Techniques



Automated Testing





Start with evaluation of the relationships between different parts of the system

Evaluate different design alternatives

Follow design guidelines

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Use design checklists

Arrange design reviews

Perform stress analysis and derating of components

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Failure Mode, Effects and Criticality Analysis (FMECA)

identifies potential failure modes

lists the effects of failures

basis for eliminating mission-critical, single-point failures

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Hardware

Design

FMECA

Component

Data[Base]

Failure

Modes

Failure

Effects

Failure Rate

& Criticality

Numbers


Failure Mode, Effects and Diagnostic Analysis (FMEDA)

includes diagnostic coverage

(the ability of any automatic diagnostics to detect failures)

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Hardware

Design

FMEDA Component

Data[Base]

Failure

Modes

Failure

Effects

Failure Rate

& Criticality

Numbers

Diagnostic

Coverage

FMECA - EXAMPLE OF DA FORM 7611

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FMECA - EXAMPLE OF DA FORM 7612

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Redundancy

duplicating critical parts

usually in the case of a backup or fail-safe

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Software Development Plan

Describing software development methodology and techniques

including reviews, coding standard, and testing.

Key aspect of the software reliability program.

The software reliability depends on the number of software faults.

Testing is very important for software:

every individual unit

integration

full system

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Design for Test (DFT)

make it easier to implement low level manufacturing tests

Built-In Test (BIT)

to achieve high reliability for a lower cost

Automatic Reset Features

restart if critical events

lack of communications, or

improper software operation.

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Typical Board with Boundary-Scan Components

Source: Corelis


Thermal Analysis

good working temperature for every chip

to achieve the required design for reliability and performance

Electromagnetic Analysis

good electromagnetic compatibility (EMC) design

for correct operation of different equipment in the same electromagnetic environment

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Accelerated Testing

using high stresses to get failures quickly

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Root Cause Analysis (RCA)

to correct or eliminate root causes

a tool of continuous improvement

Reliability Growth Analysis

collecting, modeling, analyzing and interpreting data

learn improvement done in the reliability of a product

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RELIABILITY PREDICTIONS


A quick reliability analysis for the designed system is needed

MTBF is often used as a measure for reliability

Restricted to operation under stated conditions

Important to use a relevant prediction calculation procedure

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http://www.datarespons.com/templates/interrupt.aspx?id=1812


Abstract from reliability analysis checklist in MIL-HDBK-217

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Factors that affect the MTBF figures from vendors

Prediction methods

Predefined conditions

Quality level of components

The source and assumptions for the base failure rate of each component type

The vendors’ assumptions need to be understood.

MTBF – a indicator of reliability

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What is the use of reliability predictions?

assessment of whether reliability goals (e.g. MTBF) can be reached

identification of potential design weaknesses

evaluation of alternative designs and life-cycle costs

the provision of data for system reliability and availability analysis

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FRACAS & DATA PROCESSING TECHNIQUES

FRACAS & DATA PROCESSING TECHNIQUES

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Topic Areas:

Relevant Themes:




Automated Testing



FRACAS

FRACAS: Failure Reporting And Corrective Action System

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Pareto chart: To highlight the most important among a (typically large) set of factors.

The most frequent fault causes will vary from item to item.

“No fault found” and “Root cause unknown” will often amount to a larger part of all cases.

DATA ANALYSIS: PARETO CHART

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DATA ANALYSIS: NO FAULT FOUND

Some possible reasons for no fault found (NFF):

a seldom failure hard to recreate (e.g. failure under special conditions)

the failure is coming and going (e.g. a loose connection)

there has never been a fault on the item

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DATA ANALYSIS: INTERMITTENT FAILURES

Intermittent Failures:

The system performs incorrectly only under certain conditions, but not others.

Can cause the same system failure if reinstalled, and can therefore generate high costs.

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DATA ANALYSIS: PARETO CHART

Example – summarized The following categories in particular need attention:

1. Power circuit 2. PCB production / assembly 3. Input/output circuit 4. Firmware 5. Connectors or internal cables

Also often relevant for some items: 6. Secondary storage / external memory (disk) 7. Mechanical damage 8. Batteries 9. Software 10. CPU module 11. Others – for instance

short circuit internal memory (RAM) fault defect fan errors in procedure design fault

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PRODUCTION AND REPAIR


Some relevant topics:

Errors during production tests and field errors will correlate

Follow-up of suppliers

Production batch volume for electronics

Saving test data so that analysis is easily

ISO 20815 standard – Production assurance and reliability management

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IPC-A-610 - Acceptability of Electronic Assemblies

IPC J-STD-001 - Requirements for Soldered Electrical and Electronic Assemblies

IPC product classes:

CLASS 1 - General Electronic Products

CLASS 2 – Dedicated Service Electronic Products

CLASS 3 – High Performance Electronics Products

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Rework

implies a risk for the reliability, and therefore it should be requirements about the maximum allowed rework

should be substantiated and documented for each serial number

IPC-7711/7721 is the IPC standard for rework, modification and repair

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HANDLING ELECTRONIC ASSEMBLIES

Electrostatic discharge (ESD) can occur with no visible signs of damage.

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HANDLING ELECTRONICS ASSEMBLIES

Two simple principles of electrostatic safe handling are:

1. Only handle sensitive components in an ESD Protected Area (EPA).

2. Protect sensitive devices outside the EPA using ESD protective packaging

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TESTING

TESTING

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Topic Areas:

Relevant Themes:




Automated Testing



AUTOMATED TESTING

Why automated testing?

human errors can be minimized

more thorough testing

enable monitoring of variations in test results

do several tests very quickly and find potential points of failure

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AUTOMATED TESTING

Automatic Optical Inspection (AOI)

takes time to set up correctly

Automated X-Ray Inspection (AXI)

in many ways similar to AOI except that it can look through IC packages

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Example from Axiomtek

AUTOMATED TESTING

In-Circuit Test (ICT)

often limited when pins for contact don’t get access on boards

Manufacturing Defect Analyzer (MDA)

does not check the operation of ICs

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ICT example from RNS International

AUTOMATED TESTING

JTAG Boundary Scan

widely used

much of a board to be tested with only minimal access

its standard is IEEE 1149.1

boundary scan integrated circuits (ICs) connected serially on a board

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Typical Board with Boundary-Scan Components

Source: Corelis

AUTOMATED TESTING

Functional Automatic Test System

use equipment for testing the function of a circuit

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Example on a software-defined test system

from National Instruments

AUTOMATED TESTING

Built-In Test (BIT)

good accessibility to the hardware

often less-expensive tests

Loop back test

connecting transmitter and receiver on the same board

Some form of external tests will usually be required in addition to self-diagnostics

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AUTOMATED TESTING

For testing of external interfaces using a standard protocol, a software tool can be purchased for testing and data logging

By analyzing data from testing, production areas that need attention and improvement can be pinpointed.

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STRESS TESTING - ISO 13628 PART 6

ISO 13628 part 6 for subsea production control systems:

Qualification and EMC (electromagnetic compatibility):

Shock

Vibration

Temperature

EMC tests

ESS (Environmental Stress Screening) during production:

Random vibration

Thermal cycling

Burn-in

Final functional test

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BATH TUB CURVE

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HALT - HIGHLY ACCELERATED LIFE TESTING

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Source: Turin Networks

HALT

to provoke failures commonly seen after long-term use within a relatively short period of time

take corrective measures – either changes to the design or changes in the production process

http://literature.chart-ind.com/getproductfile.ashx?id=54

HALT - HIGHLY ACCELERATED LIFE TESTING

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Typical tests are:

Cold Step Test

Hot Step Test

Rapid Temperature Cycling Test (e.g. 60°C/minute ramp-rate)

Stepped Vibration (random) Test

Combined Environment Stress

HASS - HIGHLY ACCELERATED STRESS SCREENING

HASS

production equivalent of HALT

to find manufacturing/ production process induced defects

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Source: Turin Networks

Common screen varieties

http://literature.chart-ind.com/getproductfile.ashx?id=54

RELIABILITY PROGRAM PLAN


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Topic Areas:

Relevant Themes:




Automated Testing





include required activities, methods, analyses, tools, and test strategies for the system

important to reach the required reliability

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