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Dice Before Grind (DBG) for Medical Devices

Posted by Jonny Corrao on Thu, May 12, 2016 @ 12:11 PM

CORWIL was recently approached by a medical customer who had developed a tiny wearable device that included a small bare die with innovative packaging. The product required a very small and strong die due to the customer’s very tight and unconventional package requirements. The die were on a 300mm wafer and had tight streets and low-k dialectrics.

Knowing that the backside and edge quality were key, the CORWIL team used Dice Before Grind (DBG) to reduce die breakage and chipping typically caused by the conventional method. DBG reverses the usual process of fully dicing the wafer after grinding. In DBG, the wafer is first trenched, or partial-cut, to a depth greater than the final target thickness. The wafer is then thinned to the final target resulting in die separation. After grind, the wafer goes to the in-line DBG Mounter, which mounts the wafer and gently peels off the protective grinding tape, completing the process.

Since the die are singulated at the final target thickness, wafer-level breakage is greatly reduced. Additionally, as a result of the die separation occurring during the grinding process, the backside chipping associated with thin-wafer dicing is kept to a minimum. DBG can also provide improved die strength depending on the application. For these reasons, DBG is an excellent process for processing wafers with high-quality backside requirements.

Top: DBG Bottom: No DBG
 
 
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Assembly and Test Open House Success

Posted by Susan Campbell on Sun, Mar 01, 2015 @ 10:53 PM

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Thank you to all of our customers, colleagues and friends who attended our Open House on Wednesday! Visitors were able to take a tour of our newly combined assembly and test facility. The 'under one roof' location allows CORWIL to efficiently take a customer’s device from the beginning, wafer probe, to wafer prep and package assembly, perform package final test, then scan/bake/tape & reel, and into FGI or direct ship to the final end destination.  

If you were not able to stop by, please give your sales rep a call and schedule a tour. You can also take a look at what CORWIL Technology can offer by checking out our video.

What is Wafer Thinning?

Posted by Jonny Corrao on Mon, Sep 30, 2013 @ 09:05 PM

wafer-thinningWafer thinning is the process of removing material from the backside of a wafer to a desired final target thickness. The two most common methods of wafer thinning are conventional grind and chemical-mechanical planarization (CMP).

Conventional grinding is an aggressive mechanical process that utilizes a diamond and resin bonded grind wheel mounted on a high speed spindle to perform the material removal. The grind recipe dictates the spindle RPM, rate of material removal, and the final target thickness of the work piece. Harder materials like sapphire typically require slower feed rates compared to more forgiving materials like silicon.

The wafer is positioned on a porous ceramic rotating vacuum chuck with the backside of the wafer facing upwards (towards the grind wheel). Both the grind wheel and wafer chuck rotate during grind. Deionized water is jetted onto the work piece to provide cooling and wash away material particles generated during the grind. A grinding tape is applied to the front side of the wafer to protect the devices from being damaged during thinning.       

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For conventional grinding the thinning is a two-step process. 

  1. The first step is a coarse grind that performs the bulk of the material removal. 
  2. The second step is a fine grind. The fine grind typically removes 30µm of material or less and provides the final finish on the backside of the wafer. Standard finishes for conventional grind include 1200 grit, 2000 grit, and poligrind.

1200 grit is a rough finish where the grind striations are clearly visible. 2000 grit has improved roughness compared to 1200 grit and the grind marks are less apparent. Poligrind is a near-mirror finish with the smoothest roughness. Poligrind also provides the highest wafer and die strength as the high grit wheel removes the most subsurface damage. As a rule, as the grit increases the wafer strength and smoothness improves while the wafer warpage and subsurface damage decreases.

Polish is another finish of conventional grinding. A polished finish is a mirror finish. This provides the least warpage and highest die strength of all finishes. Mechanical polishing requires a separate process and equipment from conventional grinding. Mechanical polishing is a minimal removal process of only 2-3µm of material and is typically only performed on silicon.  

In CMP, abrasive chemical slurry is used with a polishing pad to perform material removal. CMP provides greater planarization compared to mechanical grinding, however, it is considered a “dirtier” and more costly process. The wafers are mounted to a backing film, such as a wax mount, which can be difficult to remove or leave a residue on the front side of the wafer. 

CMP does have the advantage of being more forgiving when it comes to processing
hard or exotic materials like tungsten, but the cost-benefit and cleanliness of mechanical grinding compared to CMP should always be factored when determining the method of wafer thinning.