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Case History No. 2: General Electric, Electronics Lab., Syracuse, N.Y.

Case History No. 2: General Electric, Electronics Lab., Syracuse, N.Y.

By John Boucher, President, Thermocarbon, Inc., Casselberry, Florida

Reprinted from “The Resin-Bonded Diamond Blade for Dicing Hard, & Brittle Materials.” February, 1981

 

Comment: Previous attempts to utilize the resin-bonded blade for this application proved fruitless. The blade would break at first entry or after just one cut through the material. The substrates were being mounted on tape for ease of handling and in turn mounted onto a vacuum chuck.

The first step in setting up an efficient sawing system for this application was to remove the existing single jet coolant nozzle assembly and replace it with a new spindle shroud equipped with fully adjustable dual nozzles for improved cooling at the cutting interface.

The flanges were found to be out of parallel due to poor manufacturing techniques. Permanent distortion of the flange was also attributed to the use of excessive torque when affixing the flange/blade assembly to the spindle. A microscopic inspection of the bearing surfaces of the flange revealed diamond particles imbedded in the surface due to earlier blade changes and breakage without the use of intermediate cleaning and/or lapping procedures. New flanges were substituted along with instructions for proper maintenance of the bearing surfaces in between blade changes. A torque wrench was acquired for securing the flange assembly to the spindle under the recommended specifications and adopted as mandatory procedure.

The thicker substrate indicated the greater problem, for obvious reasons, and this was due to mounting the substrate to 0.003 in (0.076mm) thick plastic film. The film was not capable of providing a rigid mount in relation to the amount of work to be accomplished under the existing operating system. Waxing the substrate to silicon or glass provided for excellent rigidity. It also insured straight, parallel cut edges in the workpiece due to the ability of the blade to pass through the workpiece and well into the thicker “nonplastic” carrier.

Finally, a resin-bond blade with a 9 μm diamond particle size and RLX internal matrix was selected along with blade exposures of 0.020 in (0.508mm) and 0.040 in (1.016mm) respectively.

Subsequent dicing indicated that the best results came in “hard mounting” (wax to carrier) versus “soft mounting” (tape) with regard to dimensional control and G.E. now uses this method for both substrates as well as for other materials such as quartz and ceramics. Speeds for dicing the gallium arsenide remained at 30,000 RPM and typical feed rates are between 0.020 in/s (0.508mm/s) to 0.035 in/s (0.889mm/s) to insure optimum edge quality in the finished parts. G.E. stated that if they had to select the improvement that contributed the most to their success for dicing these hard materials with the resin-bond blade it would be their concern for the proper use and care of flanges.

Blade thicknesses are between 0.0015 in (0.038mm) and 0.002 in (0.051mm) and the department responsible for dicing is requesting that their design engineering group increase street size for ease of dicing the thicker gallium arsenide substrates. Material cost should not be a consideration when compared to the higher costs associated with losing circuits at the die separation phase or the cost of complete failure for processing the material. This is not to say that streets should be designed to extremes but rather that street width is a function of the work to be accomplished, the desired cut quality, and targeted output. Street allowances for dicing are additional variables worth equal consideration when designing an overall efficient sawing system for an improved bottom line.

Material: Gallium Arsenide,
0.004 in (0.102mm) thick
0.020 in (0.508mm) thick
Spindle Speed: 30,000 RPM
Blade Type: Metal-bond, 0.0008 to 0.0015 in thick (0.020 to 0.038mm)
Problem: Excessive edge chipping, low blade life, and blade breakage
Solution: Set up procedures for utilizing the resinbond blade for high quality cuts

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