Flame Polishing of Plastic Surfaces to Improve transparency of cut plastic surfaces

Stable flames created with the SPIRFLAME® equipment are ideal plastic surface polishing tools. A cut plastic surface of Acrylic glass (known also as Plexiglas® and other company specific tradenames) has a dull and rough, a not very appealing look. Mechanical polishing procedures are known and established. Such mechanical abrasive polishing methods are connected with intensive fine dust creation and fine dust penetration into almost everything (lungs?). Also the automated abrasive polishing only works well with flat and simple structured forms. If such a rough acrylic glass surface is inspected under a microscope then this is a combination of valleys and peaks. Mechanical polishing transfers all peaks down to the valley level.

Flame polishing is an elegant approach to flatten and transfer the peaks materials into the valley by a simple melt / reflow process. Provided there is a chemically defined and stable and heat stabilized flame environment then these peaks are easily molten down into the valley. Within parts of a second the peaks and part of the valleys do melt into a thin liquid lake and then rapidly cooling into a shiny and transparent ice, sorry, acrylic glass surface. The combustive flame environment should not chemically attack the molten material, it should rather protect the molten surface against oxidation. The ideal flame environment for plastic polishing is the spirflame®. Many plastics can be polished, but first the proper exposure parameters must be experimentally established. More details from SPIRFLAME®.

Flaming Polishing

Flaming of Plastic Surfaces to Improve Adherence of Marking or Printing Inks
Flaming of Plastic Surfaces to Improve Adherence of Glues or Adhesives

High temperature flames created with the SPIRFLAME® equipment are ideal surface treatment tools to improve the adherence of marking inks on plastic surfaces. Also the adherence of glues and adhesives on certain plastic surfaces is considerably improved.

Theory:
Flames made from mechanically mixed gases have been used successfully for many years for surface treatment. "Plasma etching" is used as an alternative and gains market share.

Plasma etching uses electric charged plasma particles to bomb the surface and to break up (to activate) certain molecular bonds between plastic molecules. These "opened" molecular bonds then can accept bond relations with ink materials. This is also called "The Wetting activity of a surface material is improved".

Obviously electric charges (plasma) would and will immediately destroy electronic components embedded in such plastic material (IC package). The active element in Integrated Circuits (IC) is the CHIP. The electric circuits and components integrated into that chip would immediately be electrically damaged and functionwise destroyed.

Some chemical treatment steps using aggressive chemical compounds applied to plastic surface are also known to improve the wettability.

SpirFlaming® is the only possibility to improve the wettability of IC packages.

Flames can be made from stored bottled gas sources.
The oxygen or air is mechanically mixed with the combustible gas, for example hydrogen. Storing high pressured gas bottles is in many countries more and more outlawed due to high risk and insurance will not accept them in populated assembly areas or areas with lots of expensive equipments. IC assembly uses lots of expensive equipments and fire insurance might be unavailable. Such mechanically mixed gas flames are weak and thermal output is not stable. They are not easy to adjust, not easy to reproduce and flaming behavior can not be predictable.

Flames can also be made by an electrolytic process from on-site manufactured oxy - hydrogen gas.
Such gas is usually 2 parts hydrogen and 1 part oxygen made from distilled or demineralized water, using electricity to break the water (H2O) during the electrolysis process into its components 2H and 1O. The 2H + 1O is then again burnt into water H2O. The electric energy used to break up the water molecule is recuperated in the flame as heat energy.

Such flames have always down to the molecule level the same mixture. The flaming behavior is predictable. The flame is very concentrated and very hot. More details from SPIRFLAME®

Due to the intensive concentrated heat the total heat input into the IC component is minimized. It needs a very short contact time between the plastic surface and the spirflame to bring enough molecular layers up to the activation temperature. But this short contact time helps to minimize the total heat energy flowing into the IC package. There is a not too wide operation window for the temperature induced activation process. Therefore the heat flow (energy per second) must be stable for automated flaming lines. The worldwide patented Spirflame® flame generating equipment is that stabilized heat source and as practice shows it is virtually the only generation system used worldwide by all leading IC backend processing operators.

Attached is a helpful List of Technical Specifications on Semiconductor Manufacturing Equipments as issued by the SEMI® organization / California.

semi-org-spec