Rapido generates the optical power and uses fiber-coupled diode modules. Optical fibers guide the power to the focusing optics. The diode modules show very long lifetime and an efficiency close to 50%, therefore the energy consumption is low and cooling requirements are minimal. Depending on the work to be performed, modules with different wavelengths will be chosen.
A lens assembly focuses the laser power which melts the solder onto the working area. It is tailored exactly to the specific shape of the solder joint and the beam may be circular, elliptic or a straight line. An optional pyrometer measures the temperature in the melt pot and the electronic actively regulates the power profile.
Multiple solder heads heat various areas at the same time and a symmetrical arrangement reduces shift.
In order to achieve higher productivity, nanosystec developed the Multi Beam Optic (MBO). It generates a number of sub beams processing more than one connection in the same time – up to 40 individual spots have been demonstrated.
Application of solder material
There are several ways to deposit the solder onto the parts to be joined.
An automated dispenser moves in the right position and applies solder paste. The volume is constant over long operating hours and the solder joints are consistent in form and quality. Dispensing is easy to integrate into a production process and even difficult positions can be reached.
Preforms are another method. A small predetermined volume will be placed and melted. The volume of the preform is well defined – an advantage in the soldering process. Preforms consisting of an AuSn composition avoid the need of a flux and no vapors are generated during the soldering process. This is of absolutely paramount importance if optical surfaces have to stay clean.
If the surface to be joined are already tinned, the soldering process works without further application of solder. Typically the solder is deposited by a vapor deposition process with a thickness of a few µm. This in beneficial to minimize shift during the cool down period.
Hot bar heating processes multiple solder joint in one effort and serves as addition to laser soldering – especially for processes consisting of different assembly steps. Compared to selective laser soldering, hot bar is a contact method. A strong current flows through the bar and the generated heat is transferred to the parts where soldering takes place. The bar may be a straight line or curved to provide full contact with the device. The actual temperature on the bar is measured and a control loop maintains the selected temperature or temperature profile.
Monitoring via a CCD camera through the solder optics gives an assessment of the solder joint quality. In addition, the collinear vision allows for precise positioning of the laser spot.
The powerful machine vision package uses various illumination techniques in order to obtain unambiguous pictures. Its algorithms include all standard techniques. Specific evaluation routines combine various techniques in one process step and deliver repeatable results in short time.
VersaSolder works as a single station or can be integrated into production lines. Trays for single or multiple devices sets, belts and feeders present the parts for processing and serve for the exchange with other work stations in the line. In addition, VersaSolder controls robots for device loading.
Precise non-contact heating
Beam shaping options
Active temperature control
Combination with hot bar method
Integration into production lines
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