Previous articles on the NAND architecture started at the basic NAND cell and built up to the NAND die level. We go up one more level in this article to discuss common NAND component packaging options.
The NAND die themselves are relatively fragile and require special equipment for placement and bonding. Typically NAND die are placed inside a protective component package as opposed to directly on a circuit board. Most follow an open industry standard defined by JEDEC.
These components allow a manufacturer to place a single or several NAND die inside one package with a standard pin-out of typically a TSOP or BGA package. The standard packages are easily handled by the pick and place systems as they adhere the parts to printed circuit boards (PCBs) prior to being run through soldering machines.
A simple single NAND die BGA component package image is shown above. There is a substrate which has a NAND die attached to it. Wire bonding machines connect the NAND die to the substrate which has via connections to the balls on the bottom side. After the wiring is complete, a molding compound encapsulates the top of the substrate providing for a rugged physical package.
The illustration below shows a cutaway of a NAND component with multiple layers of die stacked on top of each other to create a single large capacity NAND memory device.
There is an insulating layer between each NAND die and connections are made from each NAND die to the substrate using a wire bonding machine. The substrate is like a very thin PCB (Printed Circuit Board) which is the base for the stacked die. As with the single die cutaway shown earlier, the entire top of the component is encapsulated.
If the parts share a JEDEC standard form factor, the parts appear physically identical regardless of the number of die inside.
This illustration shows a NAND die in a TSOP package. There are a couple of difference with the TSOP package from the BGA package. First, there are leads as opposed to balls that take the connections from the NAND die to the outside world. Second the entire assembly is encapsulated, not just the top. The only exiting connection is the end of the lead frame. As with the BGA package, multiple die can be stacked inside of a TSOP package.
Future articles will look at putting the NAND components and a controller together to create a Solid State Drive as well as the challenges required of the SSD controller technology.
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Continue to Blog #7: Basic Controller Overview or learn all about Solid State Drives: