Testing environments simulate a variety of conditions, such as extremes of temperature, different pressures, or accelerated aging, to determine the reliability of products. Such environments naturally require most other variables to be held constant. Restrictions on variable fluctuation may require the space to be within <1 °C of a particular temperature and <2% RH of a given humidity level.

Such stringent conditions require robust and reliable equipment. CFW is in a position to provide the necessary testing ovens for electrical product tests.

• Electrical Product Lifecycle Test Ovens
• Electrical Product Heat Test Ovens

It pays to know the expected lifetime of one’s product before putting it on the market, especially if one can offer a guarantee to one’s customers. Lifecycle test ovens help one to determine product reliability and flaws by subjecting it to harsh conditions. These may simulate the wear and tear it will undergo across a long period of time or simply determine what its limits are.

Accelerated life cycle testing might subject the item to changing temperature, humidity, altitudes, pollutants and vibration levels as well as electrical and engine loading and structural loads. In the case of electrical products, a circuit board might be tested with a variety of power sources, controllable electrical loads using a load bank and high temperatures. There are a variety of approaches to lifecycle tests.

Highly accelerated lifetime tests (HALT) subject the product to conditions that go beyond what it is likely to experience from end users, but any possible defects that can cause product failure after the product is released become apparent. The goal is to find failure modes and operational and destruct limits. HASS (Highly Accelerated Stress Screening) is commonly performed in conjunction with HALT to identify production problems. Environmental Stress Screening (ESS) is used to ‘sift out’ units and components that are less reliable.

These tests are useful tools to help identify areas of possible product improvement and to make sure that the product will perform reliably under various conditions. Accelerated testing paradigms result in faster development than older testing methods, while optimal product performance in test ovens translates into optimal performance in the field.

Markets demand product reliability, and to gain a market advantage through fast and reliable product testing, the right testing equipment is essential.

Thermal testing is a key element of assessing product performance and market potential. Determining whether a product will perform under a range of possible temperatures requires a heat test oven. Various stages of product development can benefit from thermal testing, including prototype evaluation, research and development, accelerated stress and reliability testing and failure analysis.

Knowing the product quality and life expectancy of one’s electrical items can increase one’s profits in several ways. Customer confidence is boosted, which helps to support sales, and product development times may be reduced, which leads to lower costs. After-sales services can also be reduced.

Selecting the right test oven can be a perplexing process. There are many variables that must be taken into account in order to find the equipment that will produce adequate test results. The test requirements, the shape and size of the UUT (unit under test) and the availability of resources in the facility in question will determine the required oven design.

Ovens may transfer heat to the UUT by means of convection, conduction, or radiation. Most commercial testing ovens use convection. The rate of convective heat transfer will be influenced by the rate of absorption of the UUT (thermal inertia) and the resistance of the gas film around it. Thermal inertia can be modelled as capacitance in mechanical systems. The response will resemble electrical current flow in a circuit with capacitance.

The size and positioning of blowers in the test chamber are of vital significance. This will affect oven efficiency as well as the characteristics of heat transfer between the UUT and the ambient air. The blowers must have the capacity to generate enough airflow to produce turbulent flow patterns in the chamber. Disrupting laminar (smooth, layered) airflow in this way will reduce the insulation effect of the thermal and fluid dynamic boundary layer, increasing the efficiency of heat transfer. The greater the air velocity, the greater the likelihood that turbulent airflow will occur will be established.

However, there is a trade-off involved, since the higher airflow velocity will increase air temperature. This can make it more difficult to achieve the desired temperature set point and possibly require additional cooling.

This is what makes the right sizing of blowers so important: they must establish correct flow properties without unduly increasing ambient air temperature. In addition, free flow convection must be checked, as it will produce unwanted temperature gradients through stratification, hotter air settling at the top and cooler air below. This can be prevented by selecting an oven designed to let air circulate from the top to the bottom to mix hotter and cooler air.