Time & Money Saved with New 'HD' Stencil Material

Wall geometry, flexibility and environmental issues are the major considerations that have led laser cutting to surpass etching technology in

the production of PCB solder stencils. Laser cutting is the ablation (or evaporation) of material under an extremely fine focused beam. A natural consequence is the build-up of localised heat around the cutting area. As trends move towards a higher density of pads, and therefore more cutting in a given area, the dissipation of this heat is critical. This can be compounded further as thinner stencil material is utilised. Inevitably �hot spots� will form as cutting density is increased.

Stencils are cut from fully hardened stainless steel due to the desirable properties of durability, solder release properties and ease of precision cutting. Such material is traditionally cold rolled during production and will contain internal stresses. If this material is heated to adequate levels localised annealing (or softening) of the material will occur. �Hot

spots� from laser cutting can therefore result in areas of the stencil becoming irregular, or wavy �a highly undesirable property in a stencil.

Alteration to cutting sequences is a possible solution, however in an essentially serial process �time is literally money� and optimal cutting sequences are critical. Introduction of a cooling system is another possibility, but this has proved difficult to control within the precise

location of the cutting area. Attention has therefore turned to the stencil material. If a less than fully hardened material is used the tendency towards localised annealing and an irregular surface is reduced, however durability, and therefore stencil life, is considerably compromised.

�Datum HD� tackles these problems head-on and is the only material of its kind in the industry. Through innovative processing techniques Datum Alloys, has developed a fully hardened stainless

steel designed specifically for high-density stencil production. Independent testing has demonstrated dramatic and repeatable improvements in surface flatness, cutting time, durability, heat capacity and product lifecycle without sacrificing print accuracy - or the need for additional cooling.

23rd July 2002

www.datumalloys.com