Dicing Hard Brittle Materials (1063250), страница 2
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This eliminates the lip effect and the cracks at the bottom of thesubstrate. In this case the blade wear is far from the substrate (figure 25 - see also figures16 and 17).Common supporting substrates are: sintered lava, glass, unfired ceramics, ferrites andothers.H e a d q u a r t e r s – Advanced Dicing Technologies Ltd.www.adtd i c i n g . c o m Advanced Technology Center, Haifa 31905, Israel, Tel.: 972-48545222, Fax: 972-4-8550001A lava substrate also acts as a cleaning media to clean and open the diamond blade.Another advantage is the ability of the wax to flow and fill the gaps of a non flatsubstrate. This sometimes is the only method to clamp such substrates (figure 26).DisadvantagesHandling the wax process, mainly dismounting and cleaning the substrate (dies) after thecutting process, is the main disadvantage.Compared to tape mounting, which is a clean process which can also be automated, waxmounting is slower.
It requires a heating cycle of the substrate. Handling is relativelymessy.In some applications heating the substrate or cleaning with solvent after the dicing isdamaging to the product. Therefore, the wax process cannot be used. It also cannot beused for all applications requiring a die attach process (figure 8).Dicing Problems Related to Wax Mounting and RecommendationsProblem A: Loosening small die during the dicing.Recommendations1. Make sure there is adequate coolant flow and proper nozzle alignment. Hightemperatures during the dicing can soften the wax and cause the dies to move.2. Slow the feed rate3. Lower the coolant flow.
Too high water flow can loosen the dies.4. Improve the wax mounting technique to eliminate air gaps between the substrate andthe supporting substrate.5. Consult with your wax supplier to find a wax with better bonding characteristics.Problem B: On nonflat substrates wax does not fill all the gaps between the substrateand the supporting substrate, causing poor cut quality mainly at the bottom of thesubstrate (figure 27).H e a d q u a r t e r s – Advanced Dicing Technologies Ltd.www.adtd i c i n g .
c o m Advanced Technology Center, Haifa 31905, Israel, Tel.: 972-48545222, Fax: 972-4-8550001Recommendations1. Use higher temperatures for better wax flow characteristics.2. Improve your mounting technique; use higher pressure.3. Consult with your wax supplier to find a wax that will flow better.Figure 28 Typical wax/adhesive materials on carriersWax / Adhesive on CarriersA few products are available providing wax or other adhesives on carriers. Theseproducts are activated by temperatures ranging from 80° - 150°C.
The carriers are hardmylar .002" up to .015" thick, paper carriers, mesh type reinforcement and others (figure28).While the mesh type materials are homogeneous with a mesh reinforcement in the center,the mylar type consists of a layer of wax/adhesive on one side or both sides.Handling the wax/adhesive carriers is easier mainly because they are ready to use withoutside dimensions close to the substrate size and the fact that the wax/adhesive layer isuniform.The mounting process can be performed either manually on a hot plate or with additionalmechanical fixtures for better accuracy.H e a d q u a r t e r s – Advanced Dicing Technologies Ltd.www.adtd i c i n g . c o m Advanced Technology Center, Haifa 31905, Israel, Tel.: 972-48545222, Fax: 972-4-8550001The main concern is to eliminate air gaps and to achieve parallel clamping of thesubstrate to the carrier.Small bench-type instruments are available for substrate mounting.
They are designed forbetter accuracy and to optimize the bonding process between the substrate and the carrier.Problems and recommendations of the wax/adhesive carriers are very similar to the waxprocess. (See problems in the dicing process related to the wax mounting andrecommendations).To summarize this section, the wax/adhesive carrier method is easier to handle. It offerssome advantages in accuracy. But it is more expensive to use. On the other hand, themylar material in some cases overloads the dicing process, especially when dicingonly into thick mylar and not completely through into a supporting substrate (figure 29).Any dicing process that can handle substrates with regular wax mounting is probablymore economical to use.
But it is a good idea to evaluate both options during theoptimization period of the process.Mechanical FixturingMechanical fixturing is used on complicated parts with a geometry that makesconventional clamping very difficult or impossible. Other special mechanical fixturing isused on high productivity applications where the load and unload cycle time is a majorfactor in a mass production mode.Cutting completely through parts that are only mechanically clamped creates qualityproblems mainly chipping at the bottom of the cut.
Figure 30 describes a typical cutthrough on a substrate clamped mechanically. The blade cuts through the substrate into arelease groove in the fixture base. The main problem is the back side of the substrate nothaving a firm support at the cutting area and therefore chipping is higher.H e a d q u a r t e r s – Advanced Dicing Technologies Ltd.www.adtd i c i n g . c o m Advanced Technology Center, Haifa 31905, Israel, Tel.: 972-48545222, Fax: 972-4-8550001Another problem related to mechanical clamping is too much exposure due to themechanical clamps thickness over the substrate. This can cause vibrations and will affectthe cut quality (figure 30).
To minimize the vibrations, the thickest possible blade shouldbe used.Examples of Mechanical ClampingThe following is a discussion of two typical applications requiring unique mechanicalclamping.Hard Alumina trimming:This is a high volume mass production application. The request is to trim a hard alumina99.6% .025" thick on 4x sides to a given dimension (figure 31).H e a d q u a r t e r s – Advanced Dicing Technologies Ltd.www.adtd i c i n g . c o m Advanced Technology Center, Haifa 31905, Israel, Tel.: 972-48545222, Fax: 972-4-8550001The conventional clamping of tape mounting or wax/adhesive mounting cannot be usedin this case because of the long handling cycle time.For this application a special mechanical chuck was designed with a vacuum at the centerof the substrate to clamp the final alumina substrate; in addition, a set of mechanicalclamps were used to clamp the outside trimmed parts.
The mechanical clamps areactivated by small air pistons. This clamping is important to eliminate any movement ofthe trimmed parts that can damage the blade during the cutting process. At the cuttingarea grooves were machined in the chuck to accommodate the blade during the cuttingprocess (see also figure 30).Figures 32 and 33 illustrate this special chuck. Figure 32 is a principal sketch and figure33 is a photo of the actual chuck mounted on an ADT 780/4 saw.Fiber optic trimming:This unique application requires a length trimming of thin flexible fiber optic to a veryaccurate length dimension. Since the fibers are flexible and not straight, a specialmounting technique was designed to mount the fibers in a perfectly straight line.A V-groove principle was used for this application to hold the fibers in a straightposition.
Figure 34 illustrates the fibers before the mounting and figure 35 after themounting in a V-groove.H e a d q u a r t e r s – Advanced Dicing Technologies Ltd.www.adtd i c i n g . c o m Advanced Technology Center, Haifa 31905, Israel, Tel.: 972-48545222, Fax: 972-4-8550001Figure 33Process FlowA heavy gauge glass plate was used as a holder and a number of V-grooves werediced into the glass plate with a Micro-Swiss .050" thick resinoid blade ground to a90° V shape. The depth of the V-groove was calculated so when mounting the fibersin the V-grooves the top of the fibers are about .010" above the plate surface (figure36).The fibers were wax mounted in the V-grooves (figure 37).A second glass plate was waxed on top of the fibers (figure 38).The two plates with the fibers waxed in between were aligned and diced on an ADT780/4 saw with a Micro-Swiss 4.6" O.D.
x .020" thick resinoid blade to the finalaccurate length dimension (figure 39).The fibers were dismounted and rinsed for inspection.H e a d q u a r t e r s – Advanced Dicing Technologies Ltd.www.adtd i c i n g . c o m Advanced Technology Center, Haifa 31905, Israel, Tel.: 972-48545222, Fax: 972-4-8550001H e a d q u a r t e r s – Advanced Dicing Technologies Ltd.www.adtd i c i n g . c o m Advanced Technology Center, Haifa 31905, Israel, Tel.: 972-48545222, Fax: 972-4-8550001This article covered the most common mounting techniques used when dicing throughmicroelectronic substrates. It highlighted the advantages, disadvantages and problems.Some recommendations were made.The following parameters are of major importance when dicing through:Use a solid-supporting substrate that will hold the diced substrate firmly.Use a supporting substrate that will not overload the blade during the dicing.Use a mounting technique that will eliminate any air gaps throughout the substrate.If possible cut always deep enough to eliminate the lip effect on the bottom side ofthe substrate.The above are general basic recommendations.
Since every application is unique, withdifferent quality and production requirements, a process optimization should be carriedout to find the best tailor-made process parameters.H e a d q u a r t e r s – Advanced Dicing Technologies Ltd.www.adtd i c i n g . c o m Advanced Technology Center, Haifa 31905, Israel, Tel.: 972-48545222, Fax: 972-4-8550001.
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