Wafer bumping - stencil

Laser cut stainless steel stencil for solder paste printing on wafer

Wafer bumping stencils are characterized by a high number of apertures which lie close together in the size of 90µm x 110µm. A package density of up to 250000 openings is not unusual. The thickness of a Wafer bumping - stencil is typically between 20 to 75µm. Due to this high package density and due to the small openings high requirements on the precision of the laser cut process and the positioning accuracy are recommended. 

 The wafer bumping - stencil is influencing a lot the amount of solder and therefore the height of the bumps. The Wafer bumping - stencil from LaserJob guarantees through particularly close tolerances in material thickness of ±3µm and an aperture outline tolerance of ±3µm an ideal consistency of the transferred solder paste and has thereby clear advantages in relation to other manufacturing processes. 

LaserJob developed a special laser cut process for the Wafer bumping - stencil which guarantees a high precision and fulfils the high requirements of the component manufacturers. A special treatment of the bottom side of the stencil is needed to avoid damages on the wafer due to smallest unevenness. Therefore the squeegee side and bottom side of the stencil are treated with an ultrafine brush to guarantee a defined surface roughness of <0,9µm.

Benefits

Aperture size accuracy ± 3µm 

Aperture positioning ± 10µm

High precision of aperture diameter

Roughness of stencil surface <0,9µm 


Wafer bumping - stencil

Wafer bumping - stencil

overview of a wafer bumping stencil.

Wafer bumping - stencil

Wafer bumping - stencil

detailed view of an aperture .

Wafer bumping - stencil

Wafer bumping - stencil

overview of a wafer bumping stencil with more than 60000 apertures

Wafer bumping - stencil

Wafer bumping - stencil

printed bumps generated with a wafer bumping stencil.

What are the delivery times for wafer bumping stencils?

Standard delivery time for a wafer bumping stencil is 3-5 working days, ex works. 


How can we realize exact bump heights?

Our stainless steel materials for wafer bumping stencils are delivered with defined thicknesses, with little deviations < 2µm.  


How can we prevent damages of the wafer through the stencil?

A special treatment of the bottom side of the stencil is needed to avoid damages on the wafer due to smallest unevenness. Therefore the squeegee side and bottom side of the stencil are treated with an ultrafine brush to guarantee a defined surface roughness of <0,9µm. 





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