Quality Waterjet Newsletter – 10/25/2005

Cutting of Microelectronic Components with ASJ

Part 1 of this two-part series has reviewed an article on the application of AWJ (Abrasive Water Jet) in cutting microelectronic components. An article by Jiang et al.* on the application of ASJ (Abrasive Suspension Jet) for the same purpose will be reviewed here.

AWJ is formed by mixing abrasive particles with a high-velocity waterjet and then re-focusing the mixture with a mixing tube. The inside diameter of the mixing tube is usually 3 times of that of the waterjet. Traditionally the smallest mixing tube diameter is 0.5 mm (0.020”). The jet is a 3-phase mixture: water, abrasive, and air. The presence of air makes the jet expand, once exiting the mixing tube. ASJ is formed by pushing a mixture of water and abrasive through a single nozzle. The inside diameter of the nozzle is between 0.05 and 0.5 mm (0.002 – 0.020”). The jet is usually smaller and tighter than AWJ because of single nozzle and lack of air in the mixture. A higher percentage of abrasive (up to 70% by weight vs. 10-15% in AWJ) can be used, which gives the jet much higher power. For an ASJ to work properly, the mixture of water and abrasive should be in a form of suspension prior to discharging. The suspension can be created either by using additives or by fluidizing a vessel of abrasive with water. The following flow circuit illustrates the ASJ system (fluidizing type) that is used by the authors.

This system runs at 3.5 KW of power, 700 bar (10k psi) of pressure, and 2 l/min (0.53 gpm) of water. The nozzle is made of diamond with a diameter of 0.15 – 0.35 mm (0.006 – 0.014”). Its diameter increases about 0.001 mm (0.00004”) per hour. Abrasive can be garnet, aluminum oxide, or silicon carbide, depending on application. Typical abrasive concentration is 20-40% by weight. Cutting speed can be as high as 200 mm/s (472 ipm).

For singulation applications, ASJ is superior to traditional blade cutting because it avoids the problems of material fracturing (when cutting brittle materials) as well as blade loading and damage of material structural thermal integrity (when cutting soft/ductile materials). It can also cut curved profiles which blade cannot do. ASJ is also superior to AWJ in cutting speed, precision, and kerf size, except that it is more complicated and is not as reliable as AWJ for continuously cutting. A commercial product that couples ASJ with a precision XY table is already available for the cutting applications of microelectronic components.

*Jiang, S., Popescu, R, Mihai, C., and Tan, K., “High Precision and High Power ASJ Singulations for Semiconductor Manufacturing,” Proceedings of the 2005 WJTA American Waterjet Conference, Houston, Texas, August 21-23, 2005, Paper 1A-3

Beyond High Pressure

· Journal of Protective Coatings and Linings (JPCL) will publish a Special Report on Wet Methods of Surface Prep featuring Ultra High Pressure Water-Jetting in the November issue. If you like to reach JPCL’s readership of 15,000 commercial and industrial coating professionals and facility owners, call 1-800-837-8303 immediately to place your ad.

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