What is Reliability?

Reliability is a broad term that focuses on the ability of a product to perform its intended function. Mathematically speaking, assuming that an item is performing its intended function at time equals zero, reliability can be defined as the probability that an item will continue to perform its intended function without failure for a specified period of time under stated conditions. Please note that the product defined here could be an electronic or mechanical hardware product, a software product, a manufacturing process, or even a service.

Why is Reliability Important?

There are a number of reasons why product reliability is an important product attribute, including:

• Reputation. A company's reputation is very closely related to the reliability of their products. The more reliable a product is, the more likely the company is to have a favorable reputation.
• Customer Satisfaction. While a reliable product may not dramatically affect customer satisfaction in a positive manner, an unreliable product will negatively affect customer satisfaction severely. Thus high reliability is a mandatory requirement for customer satisfaction.
• Warranty Costs. If a product fails to perform its function within the warranty period, the replacement and repair costs will negatively affect profits, as well as gain unwanted negative attention. Introducing reliability analyses is an important step in taking corrective action, ultimately leading to a product that is more reliable.
• Repeat Business. A concentrated effort towards improved reliability shows existing customers that a manufacturer is serious about their product, and committed to customer satisfaction. This type of attitude has a positive impact on future business.
• Cost Analysis. Manufacturers may take reliability data and combine it with other cost information to illustrate the cost-effectiveness of their products. This life cycle cost analysis can prove that although the initial cost of their product might be higher, the overall lifetime cost is lower than a competitor's because their product requires fewer repairs or less maintenance.
• Customer Requirements. Many customers in today's market demand that their suppliers have an effective reliability program. These customers have learned the benefits of reliability analysis from experience.
• Competitive Advantage. Many companies will publish their predicted reliability numbers to help gain an advantage over their competition who either does not publish their numbers or has lower numbers.

What is the Difference Between Quality and Reliability?

Even though a product has a reliable design, when the product is manufactured and used in the field, its reliability may be unsatisfactory. The reason for this low reliability may be that the product was poorly manufactured. So, even though the product has a reliable design, it is effectively unreliable when fielded which is actually the result of a substandard manufacturing process. As an example, cold solder joints could pass initial testing at the manufacturer, but fail in the field as the result of thermal cycling or vibration. This type of failure did not occur because of an improper design, but rather it is the result of an inferior manufacturing process. So while this product may have a reliable design, its quality is unacceptable because of the manufacturing process.

Just like a chain is only as strong as its weakest link, a highly reliable product is only as good as the inherent reliability of the product and the quality of the manufacturing process.

How Can I Improve My Product's Reliability?

Evaluating and finding ways to attain high product reliability are all aspects of reliability engineering. There are a number of types of reliability analyses typically performed as part of this discipline.