Contrinex extended distance inductives are ‘Hot Stuff’ on PCB soldering oven

During the manufacture of computer motherboards, a soldering reflow oven is used to secure components in place on  the PCBs. Following assembly, boards are conveyed into a reflow oven, where the temperature increases progressively to achieve a predetermined thermal profile, melting the solder paste on the boards.

As each PCB leaves the oven, a sensor must trigger the customer’s control system and activate a transfer mechanism, moving the board automatically to the next process stage.

The ambient temperature immediately adjacent to the oven may reach 80°C (176°F), which has caused unacceptable rates of failure with other sensors in the past. The sensors must operate continuously in this environment with ultra-high reliability to ensure efficient production.

Extended sensing distances are highly desirable for this application as several types of motherboard, each with different component heights, pass through the oven. Long-distance sensing also allows the sensor to be positioned further from the heat of the hot PCBs.

Contrinex 500 Series Extended Sensing Distance Inductive sensors are ideal for this demanding application.  Condist technology delivers best-in-class operating distances and sensors have a continuous rating to 70°C (158°F). Trials confirmed highly stable performance even in the elevated ambient temperatures around the reflow oven. Vacuum-encapsulated electronics ensure excellent resistance to thermal shock and vibration.

Extra Distance sensors are mounted vertically on steel brackets attached to the exterior of the reflow ovens, and sense the presence of each motherboard as it passes beneath the sensing face. The operating distance is set at 10mm, eliminating the risk of collision with components on the board, and an M12-threaded metal housing allows easy positional adjustment when necessary.

As typically for Contrinex sensors, IO-Link connectivity is included as well as the choice of an industry-standard PNP or NPN interface to the customer’s control system. No additional electrical or mechanical protection is required in spite of the adverse operating conditions.

Previously, sensors from other manufacturers did not detect boards reliably and had unacceptably short service lives, causing frequent interruptions to production. Sensor replacement costs were excessive. Contrinex inductive sensors have been reliable and long-lived, providing a professional sensing solution with an attractive total cost of ownership.


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