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Soldering system provides reproducible joints

A Rofin-Baasel product story
Edited by the Engineeringtalk editorial team Feb 12, 2007

The unique rapid control of output power sets the laser apart from other means of heating for welding, soldering or surface hardening.

The rapid control of output power sets the laser apart from other means of heating for welding, soldering or surface hardening.

When coupled with a means of real-time surface temperature measurement, it becomes possible to use the laser not just to deliver the energy programmed, but to create the temperature rise required.

Specifically applied to laser soldering, this combination of technology provides a closed loop system that achieves repeatable quality assured results.

As a solution to an automated soldering problem, this represents a robust methodology, less susceptible to burning or failure to wet joints as the heat input is automatically varied to accommodate the actual joint thermal capacity and heat conduction conditions that are encountered.

Pyrometers in use for laser soldering tend to be of the single-wavelength variety, whereas those applied for laser welding or laser transformation hardening tend to be of the quotient variety, relying on two discrete wavelengths, which also eliminates temperature uncertainties due to variation of emissivity.

During recent trials reproducible solder joints were created using on-axis pyrometer vision and industrial diode lasers.

The laser beam delivery head is designed so that a single lens both delivers the laser power and collects the infra-red radiation scattered from the solder point as its temperature rises.

The desired temperature profile of the joint from the beginning of the laser pulse until the laser is switched off typically lasts around half a second.

The stored measured temperature profile during the operation can be the basis of a unique log of each solder joint performed - invaluable QA data.

Furthermore, by setting upper and lower allowed limits of the temperature measured, production faults elsewhere in the manufacturing process may be highlighted.

If there is no component, insufficient solder or poor contact/wetting, then the demand profile of laser power output will be different and an alert can be set.

Laser soldering is attractive not only because of the unique degree of control that it affords, but also because the heat from the diode laser is directed only at the region of interest - the joint itself.

Outside of this area the thermally affected zone is very small, unlike with gross heating methods such as wave or IR soldering.

The laser lends itself to high-speed automation and, being contactless, is also particularly clean.

Today's lead-free solders demand somewhat higher temperatures than older solders, a characteristic that is very simple for a laser to achieve.

Furthermore, such higher measurement temperatures actually increase the accuracy of the temperature measurement by pyrometer.

Find out more about this article. Request a brochure, download technical specifications and request samples here.

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