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Send til en ven   Udskriv26/11 2010 kl. 11:45
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SMD-baseret termisk beskyttelse til reflow-lodning

Robust SMD RTP (reflowable thermal protection) kreds gør det muligt at beskytte power-komponenter mod ødelæggelse i automotive og industrielle applikationer (in english). 

Tyco Electronics has introduced a breakthrough technology that allows manufacturers to include surface-mountable thermal protection in their standard RoHS-compliant reflow assembly process. Manufacturers can realise significant savings by moving from hand assembly to cost-efficient surface-mount device (SMD) processes.

The reflowable thermal protection (RTP) device can be quickly and easily installed using industry-standard pick-and-place and Pb-free reflow equipment. The RTP device is unique in that it can withstand multiple reflow passes with peak temperatures exceeding well over 200C and yet, in the field, will open when it detects temperatures above 200C.

The first device being introduced in the RTP product family, the RTP200R120SA (RTP200) device, helps meet some of the most stringent AECQ-based specification requirements for automotive electronics.

The RTP200 device can be used to replace redundant power FETs, relays and heavy heat sinks typically used in automotive designs, while also offering a robust solution for IT server, telecom power supply and other industrial applications. The RTP device helps protect against thermal-runaway damage caused by capacitors, ICs, resistors and other power components that can crack and fail, or from the effects of any type of corrosion-induced heating.

The RTP200 device features a low 1.2mOhm (typical) series resistance, as well as high-current DC-interrupt ratings of 200A at 16VDC and 100A at 32VDC. This thermal protection device is used to help meet the reliability requirements of automotive power electronics systems, including ABS, cooling fan and power steering applications.

The RTP200 device's 200C open temperature helps prevent false activations and improves system reliability since it is a value above the normal operating window of most normally functioning electronics, but below the melt-point of typical lead-free solders. As a result, the RTP200 device will not open if surrounding components are operating in their target temperature range, but it will open before a component de-solders and creates the potential risk of additional short circuits.

To allow it to open at 200C in the field, the RTP device utilises a one-time electronic activation process to become thermally sensitive. Before activation, it can withstand three Pb-free solder reflow steps without opening. Electronic activation timing is user-determined, and can be implemented to occur automatically at system power up or during system testing.
 
The device's thermal sensitivity is beneficial since, in some cases, failed power components may not generate a dead short circuit overcurrent condition, but instead may create a resistive short that cannot be opened by a traditional fuse. This type of event may actually reduce load current, but can still result in unsafe thermal runaway conditions. The RTP200 device helps prevent damage caused by both dead short circuit and resistive short circuit conditions.

The RTP200 device is resistant to shock, vibration, temperature cycling and humidity exposure. It is also tested to meet or exceed some of the strictest automotive AECQ environmental and life testing requirements. To simplify installation, improve system reliability and optimise thermal coupling with the PCB, the reflowable RTP200 device can be installed using standard SMD processes and does not require any special tooling or manual installation. It also helps conserve valuable board space in a cost-effective design.
 
The Pb-free RTP200 device is also halogen-free, RoHS compliant and allows for conformal coating.

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