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Infrared Cameras and Thermal Imaging Systems

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THERMAL IMAGING PRODUCTS

Model Board Comparison

EL Infrared Circuit Board Inspection System

How It Works

Infrared Thermography

All objects emit electromagnetic (EM) energy in a broad spectrum of wavelengths and in an amount that is proportional to their temperature. As the temperature of an object increases, the amount of EM energy it emits increases. The vast majority of EM energy emitted by objects is in the infrared spectrum. Infrared energy, which is invisible to the human eye, is defined as EM energy that has wavelength between 1 and 1000µm.

Infrared thermal imaging cameras are able to detect the infrared energy that is emitted by an object and create two-dimensional viewable images of that energy. The resulting infrared images represent the temperature distribution over the surface of the object. OptoTherm infrared cameras are sensitive to a specific band of the infrared spectrum between 7 and 14µm in wavelength. The majority of infrared energy emitted by objects less than approximately 200°C is within this wavelength band.

Circuit Board Infrared Analysis

The operation of circuit boards involves the flow of electrical current, which produces heat when passing through a circuit having resistance. Since thermal behavior is closely related to current flow, the temperature distribution on an operating package, component, or assembly can be a good, repeatable indication of its operational status. Therefore, infrared images of a circuit board can be analyzed to determine a board's operational status.

Infrared analysis test coverage is a function of the degree of electrical stimulation and power dissipation in the board and in its components. Circuits and components that are not electrically stimulated produce no resistive heat and therefore, cannot be evaluated by infrared analysis. In many cases, simply powering a board exercises the majority of component and circuits. In more complex boards, a diagnostic or functional test may be required to stimulate all areas of a board.

Most electronic packages, components, and assemblies lend themselves to failure analysis by infrared inspection as long as the following conditions are met.

There is a clear line of site between the camera and board

Current flows through the components and circuits that are to be tested

The external surfaces of components are not composed of bare metal*

*Bare metals (unpainted, unanodized, etc.) have very low emissivity. Emissivity is the efficiency with which a surface emits infrared energy. Therefore, bare metals generally do not emit enough infrared energy to allow accurate measurement using infrared analysis. There are, however, surface treatments that can increase surface emissivity adequately to allow effective infrared analysis. For example, thin Kapton tape is often adhered to BGAs with stainless steel tops to determine the location of an internal short.