![]() The life of the bulb is directly related to its hours of use.Īs the lamp surface changes color from heating, the effectiveness of the radiated heat can change. The lamp and lens assembly, 150 to 200W, can have a short life. Red light IR responds quickly to the on/off heating cycle, but is not a powerful method of heat transfer. If it is unfocused, the heating will not be efficient and will be diffused. The red light must be focused differently on parts of different heights, much like the focus of a camera lens. The size of the red light is condensed or expanded to alter the size of the heating area. Because of this, the delta Ts for ceramic emitters are not ideal, when compared with convection.įor red light IR, red light is generated through a camera-type zoom lens, creating a red dot. But, they will also heat black plastic connectors to higher temperatures more quickly. Ceramic emitters, which are the most well-known types of IR emitters, will efficiently transfer heat into silver pads, because they are higher power. This is not an issue with convection heating. Silver surfaces have a lower emissivity, so when heated with IR, they will not absorb radiated heat as well as black surfaces. Temperature across the complete PCB is more accurate and responsive to typically less-responsive component sizes. Convection heating technology is more equal, with a smaller delta T (temperature difference) across many devices on a PCB. There are a few reasons why convection heating is currently the preferred technology for reflow ovens in production assembly lines. With convection heating, the same profile will work on black parts, silver parts or parts with reflective surfaces, because they are not absorbing radiated heat. Rework of a component with top red light, PDR. If components are a different color, even if they are the same size, different heating profiles will need to be generated. This means that the solder under the reflective surface will be at a different temperature than that under black components. Reflective components will be heated less effectively, with the loss of efficiency due to the heat being reflected off their surfaces. Each component can have different rates of absorption, due to its material surface and color. Black-to-black surfaces have the best heat transfer rate. If heat is transmitted into a black material, it heats up faster than a lighter-colored material, such as white or silver-lidded BGAs, but, it also cools down faster. They absorb and emit thermal radiation very well. In other words, emissivity is the rate at which heat from an IR emitter is absorbed by a material.īlack components are the most efficient for radiated heating. This is how efficiently an object absorbs and emits radiated energy, in this case, heat. The transfer rate of heating with IR is commonly referred to as emissivity. Types of IR include: red light beam, which is usually low in power and used in lower-wattage lamps ceramic emitter elements, which are more powerful for high-wattage per heater quartz lamp rods, which supply bright, yellow light and are an older technology and hot plate, a style of heating with air circulating over or through the heater for higher power. The key to understanding IR is to know both its positives and negatives, how they affect each IR system and how each manufacturer addresses them differently, across various machines. While technology from competitors may vary, infrared radiation (IR) rework technology generally refers to top heat, bottom heat or heat from both top and bottom. By Paul Wood, Rework Applications Engineer, Desco Industries, Inc.
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