Many different applications require very thick material dicing in order to reach the needed size. Applications such as heat shields, imprint masks, and certain substrates require materials which are thicker than those used in other more common applications. Ceramics, glass, quartz, and some types of silicon are ideal for these applications, but may present special challenges when dicing, due to the increased thickness.
Choosing Size of Blade
The size of the blade that is needed is relative to the thickness of the material. Material that is considered thick is generally about .100” to .250” as compared to standard dicing material thickness being between .021” to .029”. When dicing material that is .250”, a blade that is three to four inches in diameter should be used. The blade thickness should also be considered, with a .020” to .030” thickness being recommended for thicker materials.
Using Multiple Passes
For best results, it is recommended that multiple passes be used to dice through materials that are thicker than .060”. To use multiple passes to dice through materials, the blade should be passed over the whole of the material, but only used to cut into the material about .015”. The blade can then be passed through the material again and cut another .015”. This technique can be repeated as needed until the blade passes through the material completely and into the mounting tape.
Scribes for Multiple Passes
When using multiple passes to cut through very thick material, there are certain drawbacks such as deviation of the blade during the first passes and excess time needed to finish the project. A scribe blade that only has about .050” of exposure can be used to mitigate the amount of time needed and minimize blade deviation. A scribe blade will cut about .040” into the material and create a guideline for all of the cuts that need to be made. The cut can then be made using multiple passes with a blade that has the entire exposure. The blade will usually follow the exact pattern of the trenches that have been cut.
Backside Chipping Complications
When cutting using multiple passes, backside chipping is another common drawback. Backside chipping can occur due to vibrations during cutting, improper feed rate, and many other factors. While tape selection and feed rate can be used to minimize backside chipping during multiple-pass dicing, cutting from both sides can also help to minimize backside chipping.
Cutting from Both Sides
When cutting from both sides, the material is first scribed through the halfway point so that multiple passes are not needed to dice through the material. The wafer is mounted normally, and then scribed from each side. The wafer must then be unmounted and flipped so that the scribe cuts are facing the tape. The cuts can then be finished from the other side using only one pass, which helps to drastically minimize backside chipping. To be effective, the measurements used to determine how far to cut from the center to the outside must be very precise and the machine that is being used must be very precise.