|Home | Articles | Forum | Glossary | Books|
2. Basic Reliability Mathematics [coming soon]
Reliability is important. Most organizations are concerned with fast time to market, competitive advantage, and improving costs. Customers want to be sure that the products and equipment they buy work as intended for the time specified.
That's what reliability is: performance against requirements over time.
A number of excellent books have been written dealing with the topic of reliability-most from a theoretical and what we call a ''rel math'' perspective.
This guide is about electronic product and equipment reliability. It presents a practical ''hands-on perspective'' based on my personal experience in fielding a myriad of different systems, including military/aerospace systems, semiconductor devices (integrated circuits), measuring instruments, and computers.
The guide is organized according to end-to-end reliability: from the customer to the customer. At the beginning customers set the overall product parameters and needs and in the end they determine whether the resultant product meets those needs. They basically do this with their wallets. Thus, it is imperative that manufacturers truly listen to what the customer is saying. In between these two bounds the hard work of reliability takes place: design practices and testing; selection and qualification of components, technology and suppliers; printed wiring assembly and systems manufacturing; and testing practices, including regulatory testing and failure analysis.
To meet any reliability objective requires a comprehensive knowledge of the interactions of the design, the components used, the manufacturing techniques employed, and the environmental stresses under which the product will operate. A reliable product is one that balances design-it-right and manufacture-it-correctly techniques with just the right amount of testing. For example, design verification testing is best accomplished using a logical method such as a Shewhart or Deming cycle (plan-do-check-act-repeat) in conjunction with accelerated stress and failure analysis. Only when used in this closed-feedback loop manner will testing help make a product more robust. Testing by itself adds nothing to the reliability of a product.
The purpose of this guide is to give electronic circuit design engineers, system design engineers, product engineers, reliability engineers, and their managers this end-to-end view of reliability by sharing what is currently being done in each of the areas presented as well as what the future holds based on lessons learned. It is important that lessons and methods learned be shared. This is the major goal of this guide. If we are ignorant of the lessons of the past, we usually end up making the same mistakes as those before us did. The key is to never stop learning. The topics contained in this guide are meant to foster and stimulate thinking and help readers extrapolate the methods and techniques to specific work situations.
The material is presented from a large-company, large-system/product perspective (in this text the words product, equipment, and system are interchangeable). My systems work experiences have been with large companies with the infrastructure and capital equipment resources to produce high-end products that demand the highest levels of reliability: satellites, measuring instruments (automatic test equipment for semiconductors), and high-end computers/servers for financial transaction processing. This guide provides food for thought in that the methods and techniques used to produce highly reliable and robust products for these very complex electronic systems can be ''cherry-picked'' for use by smaller, resource-limited companies. The methods and techniques given can be tailored to a company's specific needs and corporate boundary conditions for an appropriate reliability plan.
My hope is that within this guide readers will find some methods or ideas that they can take away and use to make their products more reliable. The methods and techniques are not applicable in total for everyone. Yet there are some ingredients for success provided here that can be applied regardless of the product being designed and manufactured. I have tried to provide some things to think about. There is no single step-by-step process that will ensure the production of a high-reliability product. Rather, there are a number of sound principles that have been found to work. What the reader ultimately decides to do depends on the product(s) being produced, the markets served, and the fundamental precepts under which the company is run. I hope that the material presented is of value.