Hi Gareth,

I am not sure this is exactly what you need, but have you ever
considered using the phenomenon of laser induced periodic surface
structures (LIPSS)?  It will not produce the cone like structures you
get with polyimide, but gives a periodic ripple structure.  The period
of the ripple is determined by the angle of incidence of the beam and is
usually given by:

        period = (laser wavelength)/(1 +- sin (theta))

where theta is the angle of incidence.  This phenomenon occurs in most
materials when irradiated at slightly below the laser ablation
threshold.

If you think this would be of any use, you can contact me off-line and I
will give you some references and/or answer any further questions.

Best regards,
Harvey Phillips

Harvey M. Phillips
Research Fellow
Institute of Materials Research and Engineering
Block S-7, Level 3
National University of Singapore
Singapore 119260

TEL: (+65) 874-4314
FAX: (+65) 872-0785

email: [log in to unmask]





ORIGINAL MESSAGE:
>Hi there,

>When ablating polyimide structures, sometimes instead of getting a
>clean finish you actually produce very small cone like structures in
>the ablated section. This phenomena is due to particles of carbon
>landing on the substrate and therefore acting as a mask.

>Does anyone know of a method of replicating this onto a copper,
>aluminium or gold substrate rather then the polymide substrate that i am
currently aware of (i.e. >what material is required to act as the small
particles for the mask, how would the particles be
>applied and at what size, what laser fluence levels are required and
>at what wavelength ?).

>Thanks very much

>Gareth Jones
>Celestica Ltd
>[log in to unmask]

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