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Tabbing Stringing Final DR 18/12/09 09:35 Page 28
in position, are kept tempered during the entire constant level of high quality while preventing the
process. Thus the difference in temperature production of faulty strings.
between cells and bus bars during the soldering is
decreased, what results in a minimization of the Soldering System
thermal stress in the cells and therewith in The combination of the soldering processes
breakage risk reduction. Finally the bus bars are resistance heating and laser beam soldering is a
cut to the correct length by a cutting unit. new feature of this application. Both these
Thereafter, a camera checks the tabbed cells for soldering methods can be carried out non-
breakage, those that are found to be undamaged polluting lead-free and are characterised by
are passed to a flip unit by means of a gripper highest-level accuracy, repeatability and lowest
system and are placed sunny side down on the possible maintenance requirements.
Issue VI 2009
stringer axis. Damaged cells are placed in a box
Resistance Soldering provided for that purpose. The tabbed cells are Resistance soldering
Source: Schmid Technology held exactly in position on the stringer unit, sunny The bonding of the ribbons to the cells is done my
Systems GmbH side down on vacuum tables, and then soldered means of resistance heating in the tabbing unit. By
together using a laser. Finally, the stringer electric current input into the ribbons heat is
advances the finished string to the hand-off produced at the soldering points. In doing so the
position and transfers the string to the Schmid- ribbons are heated from inside within tenths of a owned Layup Station for further processing. second and consequently serve as a soldering-
iron. The contactless heat input into the ribbons
Tabbing and stringing is carried out in two steps and the bus bars of the solar cells in connection
whereby minutely exact positioning of the solder with the short process duration under 1.5 seconds
ribbons on the rotating table of the tabbing unit reduce the temperature input including the thermal
and highest repetition precision are guaranteed. stress to a minimum. The uniform temperature
The accuracy of cell positioning along the linear profile generated along the entire solder
axis in the stringer unit allows production of one- ribbon–bus bar connection during this process
hundred percent straight and regular strings for the creates a homogenous, high quality solder result.
first time ever.
Laser beam soldering
The minimization of the cell and string handling In the second process step the tabbed cells are
Camera checks the from formerly seven times now down to only two then connected in series to create strings, again by
exact orientation of the times as well as the use of different stations for means of non-contact laser beam soldering, in
grids in relation to the quality control prior to and during the process and doing so strings up to a maximum length of twelve
ribbons the automatic rejection of defect cells ensure a cells are created. The bus bars get pressed all
around the soldering point by the help of feather-
pressure and get punctually and quickly bont
together via PID controlled diode laser, without
causing thermal stress to the cells.
The new Tabber Stringer combines strong output
performance (1,200 cells per hour) with a minimum
breakage rate (< 0.3 %) and space-saving design.
An upgrade of the module production line from 25
MW to 50 MW can be accomplished at low cost
and little effort and does only require minimal
additional space for the second Tabber Stringer.
The Layup Station is already prepared for this
upgrade and does not need further floor space.
The possibility of processing very thin cells from
130 Ìm and back contact cells also makes the
system an extremely interesting solution in view of
echnology Systems GmbH
current developments in solar cell production. For
special needs the application of different types of
ribbons on the front and the back of the cells is
possible. Schmid will deliver the first Tabber
Stringer to customers as early as January 2010.
Source: Schmid T
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