Laser Structuring

By ‘laser structuring’ we mean using a laser to modify the shape of a surface by ablating a pattern on the surface, or by selective removal of one or more coatings.

Applications include:

  • Patterning of coatings on glass for photovoltaic panel or flat panel display manufacture
  • Drilling of arrays of holes in wafers or metal/plastic sheets for assembly into fuel or solar cells
  • Deep engraving of graphics or alphanumerics in tool inserts for plastic injection moulding
  • Scribing lines as tear or break-out weaknesses for easy-open of packaging or burst patterns for concealed airbags

Most applications demand rapid movement of the laser over the surface and are well-suited to galvanometer (see principle described under ‘Laser Marking’)

Application Examples

Solar Cell Drilling

Laser drilled solar cell wafer

A single trepanned hole in a Si wafer

Silicon wafer based solar cells are amongst the most efficient at converting sunlight into electricity, but they are also relatively expensive and every effort is made in their development to optimise their efficiency by exposing the maximum front area to the sun. One way to help is to arrange for all the necessary connections and pads to be on the rear of the cell, eliminating shadowing from such infrastructure. Two ways to achieve this both require laser drilling:

  • Emitter Wrap Through (EWT). Here, each silicon wafer will need thousands of holes of around 65µm diameter drilling to make the connections between the active from surface and the electrical connections on the rear.
  • Metal Wrap Through (MWT). Here, holes of order of 500µm subsequently receive a metal conductive coating and only a few dozen are typically needed per wafer.

The StarDisc Q-switched TEM00 disc laser can achieve drill rates of several thousand smaller percussion-drilled hole sper second and up to 100 of the larger, trepanned holes per second. (See Q-switched StarDisc under Products)

Scribing of Easy-Open Packaging

Laser scribed flexible film package

Scribe lines can weaken packaging, but leave it airtight

Packaging can today be designed with convenient opening technology which is seen as a desirable selling feature. Most plastic film can be perforated at the web conversion stage and some can be scribed so that the package remains airtight. This applies particularly to plastic-on-foil style packages for freshness retention:

 

The StarShape series of CO2 sources are ideally suited as the 10.6µm wavelength is well absorbed by organics such as plastic, but reflected by the aluminium foil beneath.
(See StarShape under Products and Packaging Industry under markets)

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