Fred Schenkelberg — Thought Leader

Author of <a href="/creprep/">CRE Preparation Notes</a>, <a href="/on-product-reliability/musings">Musings</a>, <a href="/articles/nomtbf/">NoMTBF</a>, <a href="/book-author/fred-schenkelberg/">multiple books & ebooks</a>, co-host on <a href="/series/sor/">Speaking of Reliability</a>, and speaker in the <a href="/series/sor/">Accendo Reliability Webinar Series</a>.

This author's archive lists contributions of articles and episodes.

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Writing Skills

Technical Writing Skills for Reliability Engineers

Your peers, team mates, and management want to understand your writing. They want to quickly get your point, find supporting information, and take action.

As a reliability engineer, you write proposals, plans, and reports. You write problem statements, failure analysis findings, recommended process improvements, and much more.

You write to document a process or plan. More often you write to encourage others to take action.

Writing clear, concise missives the incite action is a hallmark of a good reliability engineer. You are doing technical writing.

You can learn to write well. [Read more…]

by Fred Schenkelberg 1 Comment

Waterfall Test Planning

A Waterfall Test Planning Approach to Product Reliability Environmental Testing

I may have the name, waterfall, used incorrectly here.

Years ago I learned from a former Apple reliability group manager how to organize reliability and environmental related testing where samples cascade through a sequence of stress conditions and evaluations. He called it waterfall testing. [Read more…]

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The Ability to Influence

The Ability to Influence Reliability Performance and Results

The role of a reliability engineer is to support the other engineers and managers as they make decisions concerning reliability.

Our ability may be well honed and effective. Or it may be fumbling or annoying. It is our ability to communicate along with our technical ability that determine our ability to influence well.

We may do analysis or testing. We follow up on failures and evaluate suppliers. What we actually are doing is influencing decisions. [Read more…]

by Fred Schenkelberg 1 Comment

ALT Allocation of Test Units

One question that you should consider when planning multiple stress accelerated life test (ALT) is the allocation of test units to the various stresses.

We want to create a model detailing the relationship between stress and time to failure. We also want to project the time to failure estimates to use conditions. Ideally, we test at nominal conditions only and gather time to failure information. We do not have the luxury of time thus explore using ALT.

One method of allocation is to place an equal number of samples with each stress level. Is that the best approach? [Read more…]

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Overview of Presentations Skills

Presentation Skills for Reliability Engineers

We often present proposals and reports. We talk about the plan or results. We want funding, approval, or action. We need excellent presentation skills.

Excellent communication skills is often on job openings. It is not there by chance. Your ability to communicate well, especially via presentations is vital for your success and the success of your reliability program.

If your team, peers, or management do not understand your proposal or report when you present, few will take the time to read the material instead. Your presentation skills provide the incentive for action from your audience. Action you can guide using your presentation skills. [Read more…]

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Fundamentals of ALT

An Introduction, Basic Steps, and Examples of How ALT Goes Wrong

Accelerated Life Testing, ALT, is a technique to estimate the time to failure pattern for an item. In short ALT allows us to shorten time. Done well it provides valuable insights into the future. Done poorly, it is a colossal waste of resources.

In this webinar, let’s talk about the various methods available to you for ALT. How to select the right approach given your specific understanding of the failure mechanism involved. And discuss best and a few worst practices when planning and conducing ALT. [Read more…]

by Fred Schenkelberg 2 Comments

Electromigration Accelerated Life Testing

Black’s Equation

Black’s equation for estimating the time to failure due to electromigration is a classic. James Black explored and wrote about electromigration in aluminum metallization within semiconductors since 1969.

He and others have explored other materials used as conductors prone to electromigration. Thus, there are a number of models and constants available to match your particular system.

Let’s take a look at the general equation for a microcircuit conductor after a brief description of the failure mechanisms called electromigration. [Read more…]

by Fred Schenkelberg 3 Comments

Metal Fatigue Failure Mechanism Accelerated Life Testing

Metal is a wonderful, strong, material. Yet under certain types of stresses metal can fail One in particular is fatigue due to cyclic motion.

Metals in a solid state have an atomic level lattice structure. This provides the strength and flexibility. It is the flexibility part that causes trouble. We don’t get the benefit of flexibility for free. As the metal bends it ‘adjusts’ the lattice to accommodate the motion. In doing so, it changes the metal properties becoming a bit more brittle, for example.

In most cases a very small motion causes imperceptible changes and loss of functionality. In some cases, like bending a wire coat hanger with the intent to break it, just a few cycles of dramatic bending is enough to break the wire.

In metal applications that experience cyclic motion and the risk of metal fatigue failure may occur during the expected duration of product use, we may need to characterize the time to failure behavior. An accelerated life test for a metal fatigue failure mechanism is not difficult, yet does take some planning to get meaningful results. [Read more…]

by Fred Schenkelberg 20 Comments

Temperature & Humidity Accelerated Life Testing

Peck’s Relationship

High temperature & humidity is a common test condition. For specific failure mechanisms, there are models available (or you can create a model) to determine the translation from test to use conditions.

These acceleration models generally only apply to one specific failure mechanisms and do not apply to a system level estimate of life. If the failure mechanism is the dominant failure mechanism for the product, then an ALT exploring just that mechanisms would provide a life estimate.

Peck’s relationship is an acceleration model for the effect of humidity on the metallization elements of integrated circuits within plastic enclosures (typically an epoxy over molding). [Read more…]

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The Case of Drones

Guest post by Dr. Amir Segal & Yizhak Bot of BQR

Introduction

Reliability engineers are equipped with an arsenal of techniques (FTA, RBD, Markov, FMEA / FMECA, SIL) for reliability, availability, safety and maintainability analysis. However, it is not always clear when to use each technique.
In order to design a safe and reliable product, reliability engineering techniques should be integrated with the system design process. This fact is well known, and today many system engineering conferences include discussions regarding reliability and safety [1,2]. [Read more…]

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Time Compression Accelerated Life Testing

The Easy One

The easiest ALT is one that you operate an item more often then operated by the customer. Removing spans of time the item is not being bent, moved, heated, etc allows you to use time compression.

For example, a home kitchen toaster may be used for a few cycles during breakfast time in your home. In the lab, we can avoid having to wait the day of idle time and just make toast more often than just at breakfast to accelerate the operation of a toaster.

Time compression ALT is also easy to understand and describe the acceleration factor to cover the ALT results to field use conditions. Let’s explore a simple example, work out the acceleration factor and how to interpret a set of ALT results. [Read more…]

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Soft Skills For Reliability Engineers

The Hard Part is often Soft Skills

There are many paths to becoming a reliability engineer.

If you are good with statistics, enjoy the detective work of failure analysis, or simply want to create a durable long lasting product, you likely found yourself in a reliability engineering role.

A science or engineering background is a great start. Time spent working with a design or maintenance team certainly help. An advanced degree in reliability engineering is another path.

The element that is often missing as a precursor become starting a career in reliability is excellent soft skills. We know the engineering and science stuff. The formulas, the testing, the data analysis. We can get stuff done in the lab or on the shop floor.

Yet to become an exceptional reliability engineer, or any type of engineer, add the ability to communicate well. Add the ability to get your point across and to wield influence to help others understand and accept your proposals, ideas, and results. [Read more…]

by Fred Schenkelberg 7 Comments

4 Different Types of Reliability Testing

Getting the Right Information from Your Reliability Testing

You cannot test in reliability any more than you can test in quality. Often reliability testing is done though, and knowing the range of testing approaches and their associated results will help you get the most information from each test conducted.

Let’s explore the types of testing that generate information useful as you develop a reliable product. There are 4 different types of reliability testing:

Discovery
Life
Environmental
Regulatory

Within each type there are many variations to the testing details and the specific results generated. Understanding the questions each type of testing has the capability to resolve is a good first step to implementing the right set of tests for your project. [Read more…]

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Fundamentals of HALT

An Introduction, Basic Steps, and Examples of How HALT Goes Wrong

The promise of HALT is to find the weaknesses in your design early in the design process. Understanding the basic concepts underlying HALT enable you do so effectively. Let’s talk about this essential discovery tool and how it fits into your program.
[Read more…]

by Fred Schenkelberg 3 Comments

4 Steps to Accomplish HALT

4 Not Always Easy Steps

Highly Accelerated Life Testing, HALT, is a method to discover the weaknesses in a design. Using a step stress approach of single and combined stresses, you can quickly expose the salient weaknesses in your design and/or assembly process.

The value of HALT is it’s quick and often finds problems not previously known. You will destroy one or more prototypes, yet the value of knowing specifically what needs improvement more than justifies the sacrifice of a few photos.

Conducting HALT may be part of your reliability plan. Keeping a few steps in mind will help make sure your HALT does provide value back to your development efforts. [Read more…]