Applied Materials solar PV screen printer features modular design

August 31, 2011 -- Applied Materials (AMAT) debuted the Pegaso screen printer -- a nod to the mythical flying horse Pegasus -- on its Baccini platform, fabricating electrical circuits on both sides of a solar cell.

The architecture features dual independent lanes (dual print heads) with closed-loop metrology for adjusting printing parameters on-the-fly from wafer-to-wafer. The system?s specifications include <8µm alignment accuracy, >2900wph throughput, a net throughput >2700wph, <0.15% wafer breakage, and handling for wafers as thin as 120µm. Jim Cushing, senior director, product management, Applied Solar, and Andrea Moretto, Global Product Management, Baccini Cell System, Solar Business Group, Applied Materials describe the tool?s architecture and design principles in a podcast interview.


The new platform continues the Baccini legacy of "very soft wafer handling" with more sophisticated motion control algorithms and the use of planar motors and Bernoulli "flippers" that are essential to the tool's performance. There is very limited mechanical handling, said Moretto, who describes it in detail in the podcast (also see the video clip below). Furthermore, the short kinematic chain design concept directly enables the system's precision and accuracy. (Short kinematic chain refers to a reduction in the number of components necessary for achieving relative motion, as well as better machine tolerances and reducing the derived stack uncertainty of the kinematic chain.) The tool also does not use bearings.

Figure 1. Scaling is no longer enough. SOURCE: Applied Materials

Applied believes that scaling of solar cell manufacturing is no longer enough to achieve the decrease in cost of module manufacture. "Over time, these economies of scale start to slow down," said Cushing (see Fig. 1). According to Cushing, about 1.5yrs ago, BoS costs became a larger factor than module cost in the drive to reduce manufacturing costs. "So what we are looking for are ways to continue to decrease not only the module costs, but also the BoS, and one way to do that is through efficiency," he said (Fig. 2). "We have to simultaneously reduce both the cost, as well as increase the efficiency."

Figure 2. Solar PV mission: lowering the cost of electricity. SOURCE: Applied Materials

With respect to wafer handling, Cushing described how wafer breakage negatively impacts a screen print production line (e.g., cost and value of the wafer, downtime for cleaning and maintenance, and chips of wafers can tear the print screen). The economic impact of broken wafers can be as much as $500k/yr with alternative screen printing systems, said Cushing.

Cushing noted that the system's modular design enables a "future-proof" upgrade path. End users are doing development of different cell architectures, as well as new printing capabilities, and new laser or metrology capabilities, he explained. Applied considers the new tool to be a kind of backbone that enables swapping out different modules/capabilities as needed over time.   

Video of the Baccini Pegaso in action:

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