CRE Preparation Notes

Prep notes for ASQ Certified Reliability Engineer exam ISSN 2165-8633

The idea of the CRE Preparation Notes series is to provide you short practical tutorials on all the elements that make up the ASQ CRE body of knowledge. The articles provide introductionary material, basics, how-to’s, examples, and practical use guidance for the full range of reliability engineering concepts, terms, tools, and practices.

Keep your knowledge fresh with regular review of topics and tools that make up reliability engineering.

- Improve your reliability engineering skills

- Learn about the wide range of tools available

- Enhance your resume with the ASQ CRE

You will find the most recent tutorials in reverse chronological order below. Below each article is the section and specific clause of the CRE Body of Knowledge that tutorial addresses. Click on those tags to find other articles on the same topic. To the right on the sidebar, there is a listing of the 7 major categories in the body of knowledge - it's a quick way to find groups of articles on each specific area. You can also use the search function to locate articles, podcasts, or tutorials on specific topics.

by Fred Schenkelberg Leave a Comment

Reliability and Risk Mitigation Actions

Once reliability risks have been identified and analyzed, we have to do something.

Well, not really.

If the risk is acceptable to the stakeholders, then we can simply continue with the current plan and monitor or any new risks or changes in our understanding of the existing risks.

Risk mitigation is a ‘system, process, or investment to control the likelihood or consequence of a risk.’ This is according to the glossary of risk terms in ISO 31000: Enterprise Risk Management. In many cases, the risk is unacceptable and will require mitigation. [Read more…]

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Determining Customer Reliability Requirements

Determining What Customers Really Want Concerning Reliability

Customers want the benefits created by your product. They want the time savings, the reduced yield loss, they want simplicity, coolness, speed, etc.

Customers buy your product to solve a problem, they do not buy it to simply enjoy the features. The features have to do something of value. They have to provide a benefit.

If your product fails, the feature doesn’t work. Customers do not realize the benefit they expected.

In short, your customer wants your product to work as expected. When asked a customer will tell you they do not want to have product failures. [Read more…]

by Fred Schenkelberg 2 Comments

The Quality Triangle and Reliability

How Does Reliability Fit with the Quality Triangle?

The Quality Triangle provides a method to establish priorities for a project. It strives to balance time, cost, and quality (or scope instead of quality). It does not include reliability.

Now I am a bit bias as a reliability engineer and believe a projects set of priorities should explicitly include reliability performance. Of course, there are many potential priorities, yet reliability certainly can make or break a product, it’s market acceptance, and an organization’s profitability.

So, given a quality triangle based set of priorities, how does reliability fit in? [Read more…]

by Fred Schenkelberg 1 Comment

A Framework for Risk Management

Making or supporting decisions involving product or system reliability is fraught with uncertainty. Is it reliable enough? Will failures occur prematurely? Are failures dangerous?

Uncertainty is risk.

In recent years more organizations and international standard bodies have focused on risk management. Identifying, analyzing, and mitigating uncertainty in a systematic manner.

There is not a set way for every organization to organize a risk management process. The ISO 31000 standard does describe a framework for the implementation of risk management within your organization. [Read more…]

by Fred Schenkelberg 2 Comments

CRE BoK and Risk Management

The New ASQ CRE BoK Group: Risk Management

The 2018 ASQ CRE Body of Knowledge has a new top-level section titled II. Risk Management.

A few of the topics, 6 of the 9, are the same or similar to topics in the previous CRE BoK. There are three new topics that extend the reliability engineers need to know, understand, and use risk management tools.

Overall the new section of Risk Management has three groups of topics:

A. Identification

B. Analysis

C. Mitigation

Let’s take a quick look at the details in this new section and highlight the changes and new elements. [Read more…]

by Fred Schenkelberg 6 Comments

Review of 2018 ASQ CRE Body of Knowledge

The new CRE body of knowledge goes into effect for exams starting January 2018.

The changes include topics that has been dropped, added, or altered. There also is a new structure with 5 main groups rather than the previous seven. Overall, the BoK remained pretty much the same with a reorganization of the topics.

Reading the new BoK and comparing it to the old BoK raises a few concerns or observations. Let’s take a look at the new structure and what the changes say about the reliability engineering profession. [Read more…]

by Fred Schenkelberg Leave a Comment

8 New Topics in the ASQ CRE Body of Knowledge

Last week we reviewed the 10+ topics removed from the CRE body of knowledge (BoK). This week, let’s look at the additions.

Three of the additions are new categories or groups of topics that in part contain new topics. There are five new topics, that in most cases included bits and pieces of concepts buried in the previous BoK.

Let’s take a look at each additions in a bit more detail. Some I agree with, some I wonder what the motivation is behind the addition, and some I question why it is included. [Read more…]

by Fred Schenkelberg 3 Comments

10+ Dropped Items from the ASQ CRE Body of Knowledge

A Review of the 2018 ASQ CRE Body of Knowledge

I just noticed the new 2018 ASQ CRE Body of Knowledge had been posted on the ASQ site. The new BoK will be in effect for CRE exams as of January 2018. Thus, we have six months to adjust to the new body of knowledge.

This is part 1 of a multipart review of the new BoK. Here we’ll look at the parts that those preparing for the exam will not have to master or review. There are 10+ topics dropped completely or in part from the BoK.

In future articles, we’ll review what has been added, what has been changed (a review), and how to best prepare for exams based on the new BoK. Plus, we can look over past BoK’s to understand where reliability engineering practice is today.

In part, the logic is these sets of tools (topics) that are not widely used by working reliability engineers. In some cases, I agree, and in others, I don’t. Let’s look at the eight topics not found in the upcoming CRE BoK. [Read more…]

by Fred Schenkelberg 2 Comments

The Eyring Model

The Eyring Model for Accelerated Testing

Sometimes the reaction rate of a process relies on two stresses. For chemical reactions temperature seems to influence the rate of the reaction. Yet, other stresses such as humidity or voltage may also play a significant role.

H. Eyring suggested a model that assumes the contribution of each stress on the reaction rate is independent thus one could multiple the respective stress contributions to the rate of reaction.

The Erying model provides a means to account for the contributions of temperature and another stress when modeling the time to failure of select failure mechanisms. [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…]

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…]

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…]

by Fred Schenkelberg Leave a Comment

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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