Engineering Mistakes, Causes, and Prevention - Industrial Metallurgists

Engineering Mistakes, Causes, and Prevention

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Engineering and producing a product or structure involves many decisions and actions, and occasionally engineering mistakes are made. Sometimes they are easy to fix and not costly. Other times the mistakes take a great deal of effort and money to fix. Regardless of their impact, many mistakes are avoidable.

The general categories of mistakes can be put into two categories – mistakes due to process or procedure errors and mistakes due to lack of competence. This article discusses these types of mistakes, their causes, and ways to prevent them from occurring.

Process/procedure error mistakes

Process/procedure errors occur when someone performs a task. Examples of tasks are performing a test or evaluation, running a manufacturing process step, or repairing a piece of equipment.

We're familiar with the task, but still make an error. Examples are connecting equipment incorrectly, missing a process step, or using the wrong material.

Chris Lewicki gives an example of a procedure error in his article My $500M Mars Rover Mistake: A Failure Story. He was working with a team of people running final testing on the Mars Rover before it was launched into outer space. During the testing he hooked up a piece of equipment incorrectly, which caused a problem that he and the rest of his team thought killed the rover. 

Lack of competence mistakes

The other type of mistake is due to lack of competence, when someone is unfamiliar with a task or does not have the knowledge needed to make a decision. They're unaware of what they need to understand and lack the competence needed to perform a task correctly or make a properly thought-out decision. Another way of saying this is it’s an error of ignorance – lack of knowledge or information.

An example is from personal experience. When I worked in an integrated circuit factory, I was responsible for a process for cleaning particles off silicon wafers on which integrated circuits were being built. Particles destroy integrated circuits.

The cleaning process involved cleaning the wafers using hydrogen peroxide followed by cleaning the wafers with an acid. I made a change to the cleaning process without a complete understanding of the reasons for using the acid cleaning step. It was a decision based on intuition.

Two months later, wafers processed through the new cleaning process finally started reaching the end of the manufacturing line (integrated circuits take a long time to build) and the product failed final testing. Lots of scrap.

The only common link between the failing wafers was the change in the cleaning process. So, the previous cleaning process was reinstated, and I had to figure out what caused the failures. I’ll explain what happened in a little bit.

Root causes of mistakes

There are different root causes for mistakes due to process/procedure errors versus lack of competence.

For process/procedure error mistakes we know the process or procedure. Mistakes usually occur when we’re not paying complete attention to the details. There are numerous reasons for this, such as being distracted, being hasty, or trying to multi-task. Maybe we got a bad night's sleep and had an argument with someone.

Process/procedure errors also occur when a process or procedure is complicated and/or has many steps and there's no written document with the steps and setup requirements or the document is not thorough.

For engineering mistakes due to lack of competence, the root cause is not having the skills or knowledge required. This can happen to new engineers or technicians who are unfamiliar with the task or decision. It also happens with people who try to use intuition or common sense. But there is no such thing as intuition or common sense when it comes to engineering and science. Either we know the engineering details and science or we don’t.

A well-known cognitive bias is the Dunning–Kruger effect, when someone with limited competence in a particular domain overestimates their abilities. Being able to recognize whether one’s knowledge or skill is a match for the situation is important.

In psychology, the four stages of competence, or "conscious competence" learning model, relates to the psychological states involved in the process of progressing from incompetence to competence in a skill.

engineering mistakes and competence hierarchy


One solution for preventing engineering mistakes due to process/procedure errors is being mindful and focused when doing things. Be aware of the situation and give 100% attention. Put your phone to the side. Don’t listen to music, have a conversation, or multi-task. For complicated or lengthy procedures/processes write and follow a checklist or standard operating procedure.

The solution for preventing engineering mistakes due to lack of competence is to gain experience and knowledge in the area of interest, and don’t try to use common sense or intuition. Learn from experienced colleagues, read books, and take training. Also, practice using the skills and knowledge in situations where the impact of mistakes is small or when someone more experienced is present to provide oversight.

For the cleaning process mistake I spent time researching the cleaning process and the effects of the chemicals on the silicon wafer surface. This involved reading many journal articles about the cleaning process and the silicon surface chemistry, performing experiments to characterize the wafer surface after exposure to hydrogen peroxide with different levels of impurities, and talking to engineers with more experience with the cleaning process.

It turned out the cleaning process change I made resulted in a 100-nanometer thick layer of aluminum being left on the surface of the wafers. This layer of aluminum interfered with diffusion of antimony into the silicon during a subsequent process, causing failure of the circuits on the wafers.

With my new understanding of the science of silicon wafer cleaning changes I proposed new changes to the cleaning process that resulted in particle reduction, reduced cycle time, and no impact on circuit performance. I went from unconscious incompetence to conscious competence.

The tricky part about lack of competence errors is for a person to be able to judge where they are on the competence hierarchy for a specific skill or subject. Oftentimes, people will have some knowledge or experience and believe that is sufficient – “enough to be dangerous”.

For engineering decisions and problems, I learned my lesson about using scientific intuition or common sense.  I do the research needed or consult someone with more expertise than me when I’m faced with a problem or decision that’s out of my area of competence. The stakes are too high for me.

At home, where the stakes are not so high, I’m willing to take on tasks where I’m at level two of the competence hierarchy and live with the consequences. For example, planting trees or shrubs in sub-optimum locations and watching them take longer than expected to grow. Or spending time trying to modify or fix my bicycles and then having to take them to the bike shop to fix my fixes. On the positive side, they were learning experiences that improved my competence. I’ll consult the bike shop before attempting modifications and fixes.

Making mistakes

In engineering mistakes, and life mistakes, will be made. Still, we can take steps to reduce their number and impact. The first step is to honestly assess our ability to perform a task or make a decision.

Check out this podcast, video, and article to learn more.

As for assessing the categories of mistakes, are there only two? Perhaps this is an area where I lack the necessary competence. Let me know. mp******@im*****.com.

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