packaging is already in use in your iPhone or your iPad.

So, I want to give you three sample cases. Two of them are where.

This, advanced packaging is used for form factor reduction.

That is to, you know, reduce the area that

these chips occupy on your PCB. And

I'll also give you one example in the case of the

image sensor for the camera for your iPhone or your iPad.

Where this this advanced packaging helps in improving the performance or improving

the image quality of your camera. So the very first place where

you can observe this advanced packaging technology being used

In the, in your smart phone is, is the microprocessor.

So, if you open up, if you open up this, A5

microprocessor chip and look at it sideways, this is how it looks.

So what you this is how it looks. So what you see if you look

at this side view.

Is that you can observe three pieces of silicon in here.

One is this, A5 microprocessors,and then there are these two chips

on top of which, which are I think two DRAM chips.

Which are stacked on top of each other,

and this microprocessor is in one, one, one package.

So this is one package. And these two DRAM chips are in this,

another package and what you have is basically this DRAM

stack DRAM package on top of this A5 microprocessor.

So this is also known as a package on package

implementation or where you have where also acronymed as PoP.

And what, again you can observe this, the

set of solder balls. So, this is flip chip ball grid array

so you can see this array of balls, solder balls

which are Connecting this microprocessors to the PCB below.

And you also see these, another set of

solder balls which are, connecting this second package.

This second DRAM package to carry the, to carry the supply voltage and

also connecting this microprocessor to the

DRAM

So, this, this is another cartoon which is depicting the same.

So, you have this first package of, so you

have these two packages. One is your microprocessor.

And then the other one is the stacked DRAM and then, there, this

microprocessor is, connected to, to the PCB below using

this flip chip package

So there are these micro bonds and then there are these ball grid array

array which connect this A5 microprocessor.

And then there also these second set of solder balls which are taking

the supply voltage from the PCB below to this DRAM chip

So this package on package implementation.

it's, it's mostly for a form factor reduction where esentially

you buy in your iphone or your ipad

or your smartphone where you're constrained for space.

You buy stacking these packages on top of each other.

You essentially achieve a form factor reduction.

So I want to quiz you on, in this package on package implementation.

Which package should be on the top?

So there could be two possible implementations.

one is, let's label one as implementation A, where

the DRAM chip is on the top of the microprocessor.

And, the option B, where the microprocessor is on top of the DRAM.

So I want to think, to guide your thoughts,

I want you to think along two directions.

Which in, one is that Which one is better from a heat management perspective.

Which option, either option A or

B is better from a heat management perspective.

The other thing I wanted you to think about

is which option is better from an I/O perspective.

Which option is better To manage the

input and output signals coming into this package.

From a heat perspective most of the

heat in this package is generated in this microprocessor.

So you'll have most of heat being generated here.

From a heat management perspective, it looks like option B might be

a better choice because in that case you can put a heat sink here

And you can have a steel plate as a heat sink

and you can better take out the heat from this package.

On the other hand in option A, you'll have this microprocessor heating up.

And that in turn will heat up your DRAM.

So if your DRAM chips heats up, then

it decreases the retention time of your DRAM cell

And you need to refresh it more often.

So it's bad for, for heating up of this DRAM chip is bad.

So from a heat management perspective it looks like option

B might be a better choice which places the microprocessor

on the top.

Let's look at it more from an I/O perspective.

So from an I/O perspective it if you think about these two pacakges.

If you have option a, you it's better from an I/O

perspective because most of your I/Os are actually coming to your microprocessor.

Because your microprocessor needs to communicate with the NAND

flash with your gyroscope, with your accelerometer.

So if you have this microprocessor on the bottom,

you could actually use this flip the, this microprocessor.

And use this flip chip package, to get your IO signals into your microprocessor.

On the other hand, if you had microprocessor

on the top, you need these wire bonds to.

bring all these signals from your PCB to your microprocessor.

So you need a whole mesh of wire bonds.

To, connect all the I/O signals to your microprocessor.

So from an I/O perspective, option b is, is bad.

So from an IO perspective, option A is the winner.

And so as

we saw in the current implementation which is used commercially,

we have this DRAM on top of the microproccesor. So probably

. It's being driven by this I/O perspective.

So second scenario where this advance packaging is used

in your smart phone is in this NAND flash memory chip.

Again, advanced packaging in this case is used for form factor reduction.

So if you pry open this NAND flash chip and

a package. And then look at the different, IC chips.

So, you see this stack of, a stack of these, ICs on top of each other.

In this case, I'm showing you a stack of 24, chips.

NAND flash chips, stacked on top of each other.

And each of them has a capacity of four gigabytes so this stack

has an enormous amount of storage capacity of

96 gigabytes in this one single package. And you

can see they are, these chips are stacked in this domino fashion.

So you have these One domino of of these chips

and then you have another domino on top of that,

and then they are connected using these wire bonds

Looking at these wire bonds it's almost incredible that you know, these chips, the

stack is functioning without these these wire bonds shorting into each other.

Right, so this is another picture.

So this is showing it from another angle, where you have

these stack of these NAND flash memory chips.

There also a controller chip, which is on the top,

so this controller chip needs to communicate with So, looking

at this you know, it, it almost looks like you

know, and if you know, Spiderman with the third hand.

And you know, you have these incredible wire bonds and none of them are shorting

with each other and it's, it's just

amazing to see that this package still works.

And There, there's been a tremendous amount of

advancement in the wire bond technology as well.

Traditionally these wire bonds used to be made, of gold but with the

gold prices going up, they're actually, now these are actually made of copper.

And but there's still a lot of inertia left in this wire bond

technology and it's very prevalent and in use commercially at the moment.