The technology trend is everything getting smaller, however certain applications require dice extraordinarily thick materials, such as glass, quarts, ceramics, and some silicon.  These applications range from making imprint masks, to making heat shields, and substrates that require an unusual or uncommon thickness.

What do we mean by extra thick material? Normally the standard thickness for any given material in the industry is about 0.021 – 0.029?, the extra think materials we try to address here is 0.100 – 0.250? in thickness.

Some challenges of dicing these types of thickness materials:

-  Need to consider blade thickness and exposure.

It is likely that when dicing something that is 1/4 of an inch in thickness, a 3 or 4? diameter blade is needed.  Also the thickness of the blade needs to be relative to the thickness of the material.  The blade needs to be fairly thick in order to accommodate the spindle load that will be generated.  A thickness of .020 – .030? is recommended for the blade.  Now there are a couple of different techniques that one might use to accomplish this task and they will require different procedures as well as yield different results.

-  Consider Multiple Passes

We recommend that when dealing with thicknesses of .060? and over, the dicing be done in multiple passes.  This technique requires the blade to make several passes while gradually cutting the whole of the material.  In other words the blade makes the first pass at say .015? into the material; on the second pass it knocks out another .015? and so on until the blade reaches beyond the tape and the cut is completed.

The draw backs are this process is very time consuming. Every cut has to be multiplied by the number of passes. And the blade tends to deviate during the first passes because of lack of support.

This can be remedied by using a different scribe blade.  Instead of using blades that gives you the entire exposure needed, we recommend using one that has only about .050? of exposure.  Scribe .040? into the material and make the trenches for all the cuts that need to be made.  Once this process is done, switch to the blade that has the entire exposure and dice in multiple passes over the trenches that were created earlier.  The second blade will tend to follow the scribe cut alleviating any waviness.

- Back side chipping

Another issue is that the bottom of the cut or the back side chips. Some of the causes are, improper cut depth, improper RPM or feed rate, and vibrations that occur while the last chunk of material is being knocked off on the last pass.  There are no good solution for this problem, however buying choosing the right thickness of the tape could mitigate the problem. It’s better to choose a tape that is sturdy and does not allow for much vibration.

We recommend using a RPM of 15K for 3 and 4? diameter blades. We also recommend 20K for 2? blades and a feed rate of about .02? per second (depending on the specs and material).  For glass and quarts we recommend using 325 grit size, for ceramic 270  and for silicon 3000 or larger.

If any questions on selecting the right blades, tapes for your task, please contact Dicing Blades engineer for recommendations.

We have covered a number of aspects of the dicing process but still there are important areas that need to be discussed. I have written about what tapes are available and what are the parameters that define the tackiness, thickness, and type of tape to utilize. And now it is time to tackle the step on how to actually mount the wafer and the type of materials used to hold the tape.

The two main mediums widely utilized to hold the tape and the wafer in place are Film Frame and Ring.

Using film frame

One medium used to hold the tape is what we call a film frame – a metal frame that is commonly used in a number of applications. Mainly to cater some machines and systems that only accept this kind of medium to hold the wafer on the table or work area. Basically, it is made up on one piece of metal and the tape just adheres to the inferior side of the frame. It is a round metal frame that measures about 0.050” thick with notches at the bottom that assemble in the work area of the machine – like what I have illustrated in the images above.

Using ring

This is another type of material used to hold the tape and the wafer. Contrary to film frame, it is a plastic hoop that is composed of two parts. This ring is quite similar to an embroidery ring made of plastic and it holds the tape in the same manner the embroidery ring holds the cloth or fabric that is going to be worked on. Basically, it uses a small and large diameter ring that assemble together holding the tape in between while slightly stretching it once it is in place. The video above shows an 8” diameter ring that is used for 6” and smaller wafers – you sure to check it out.

The mounting process

The mounting is absolutely critical regardless of whether to use a film frame or a ring in the process. It is imperative that there are no air bubbles in between the tape and the wafer because this will cause problems particularly during the dicing such as breaking of materials and/or materials falling off the tape. We could see how the materials can break since a vacuum is used during dicing – this is when there is a lump between the tape and the wafer. If the blade passes through the portion with the air bubble and the piece comes off, it could break the blade or it could scratch the rest off the wafer. To avoid air bubbles and to make it sure that you are doing proper mounting, the strategy requires that the tape is put close to the wafer without being in contact with it at first. By the use of digital pulp of the finger, the tape is then carefully pressed onto the wafer making contact and adhering to it – starting at one extreme of the wafer and slowly working across it until the mounting is done. The video above shows the technique utilized to do this manually.

Whether you use a film frame or a ring, for as long as the mounting is done appropriately, with the right kind of tape, the material is ready to be diced. This is where the machine and the parameters come into play. There are a number of processes that can be utilized such as scribing, notching, and dicing all the way through the material – topics that we will be taking-up in the next posts.