A Brief History of Semiconductor Packaging

in this video we're going to look at a

brief history of the semiconductor

packaging industry packaging refers to

the integrated circuits carrier and

enclosure it protects the Silicon dye

inside from physical damage while also

allowing it to be connected to other

devices

the industry has long been chopped liver

overshadowed by the sexier work of wafer

fabrication

but it's important and we should know

about it let's go

but first let me talk about the

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ICS are precious little snowflakes they

need protection from The Real World

which is full of damaging influences

particles can get in and interfere with

operations moisture in the air can cause

their metals to corrode high

temperatures generated during operations

can cause the IC to degrade or even fail

outright vibrations or jolts can damage

the Chip's capabilities and so on

the packaging is for protecting from all

of these threats let's talk about what's

inside first we have your die

the die attaches to a metal Support

called a lead frame oftentimes through

the use of Clips adhesive or straps the

lead frame has wires attached to it

which connect it to the outside world

these are called Bond wires

and then finally there is a plastic or

ceramic or metal enclosure surrounding

the die the lead frame and the bond

wires

this whole setup is considered by the

industry as only the first level of

semiconductor packaging the second level

refers to the circuit board and the

third and final level refers to the

system's final enclosure like the

desktop PC's chassis

the process of encasing the fabricated

die into its level 1 package is referred

to as the back end we can further break

down back-end processes to two major

steps assembly and test

processes differ based on the technology

but here is the vanilla workflow in

assembly we start by cutting the dies

out of the completed wafer and

inspecting them after this we have to

put the dies onto the package's lead

frame called die attach or die bonding

or die mounting

then we attach the very small Bond wires

to the dies which allow the chip to

communicate with the outside world this

step is called wire bonding and was

pioneered by Bell labs in the 1950s

after that we put the die into its

ceramic or plastic package to protect it

from the outside world

at the start this process had to be done

manually making it one of the first

things to be outsourced abroad since

then machines have taken over and a

swath of new bonding techniques have

been introduced discussing them is

beyond the scope of this video but you

should know they exist

throughout its history packaging's goals

have stayed rather consistent help the

IC achieve its full functionality and

don't get in its way be as small as

possible and be as cost effective as

possible

in the beginning only military or

aerospace companies use semiconductors

price was less of a concern than total

reliability

Ergo most semiconductor manufacturers

package their dies in her medically

sealed cans made out of ceramic or steel

this prevented any contaminants from

messing with the chip but there were

serious drawbacks

Ceramics and metal cost a lot they're

also heavy which meant that the circuit

boards they were attached to had to

support all that weight this made them

heavy too

packaging took a big leap forward with

who else Fairchild semiconductor

when Fairchild started producing their

revolutionary planar ICS in the late

1950s they packed them in the same t05

and flat packages they used for

transistors just with a few more leads

we will talk about flat packs a little

later in this video but first let us

talk about the t05 the to stands for

transistor outline

a t05 kind of looks like a squid

basically a metal Cannon metal lid

fairchild's first micrologic chips were

accordingly etched in a round shape

but the t05's awkward round shape made

it difficult to attach onto and arrange

on a board adding to the labor cost

worse yet t05s limited how much data the

chip can take in and push out they maxed

out at just 8 to 10 pins fairchild's New

Logic circuits needed far more than that

t05 packaging diluted the ic's

advantages and worsened its

disadvantages with this situation how

were ICS ever going to get to price

parity with germanium devices and vacuum

tubes

in response Fairchild developed two new

packaging techniques the first was

plastic encapsulation it sounds fancy

but the way they did it back then was to

put the IC die on a ceramic bead and

cover the whole thing with a plastic

blob

this method had some issues plastic can

be permeable to certain chemicals

leading to concerns surrounding

contamination and plastic can shrink or

grow depending on outside conditions

like heat inflicting mechanical stress

on the chips inside

however plopping plastic onto a chip

required very little skill this meant

that Fairchild could Outsource his

assembly work to cheap manual labor in

Hong Kong or South Korea one of the

first such electronics companies to do

so

fairchild's second idea would forever

change semiconductor packaging

fairchild's digital systems laboratory

head Rex rice created a new lead

configuration for an IC the leads were

spaced about one hundred thousandths of

an inch apart the industry term for this

measurement is lead pitch and came out

in a single line you would attach the

package to the circuit board using what

is called through hole mounting

here you insert the package's leads

through literal holes drilled into the

boards the holes have large round solder

contact areas surrounding them after

insertion you solder the leads on the

back side to secure them the method for

doing this was called wave soldering

Tess found that this new inline

packaging system fit all the criteria it

can accommodate more i o some 12 to 16

pins at the start

it simplified the circuit board layout

and finally it took less time and skill

to assemble the inline Arrangement was

Far simpler than the t05 cans circle

shaped leads

before deploying the product Fairchild

first consulted with customers and end

users who did not like the single line

Arrangement however they would be okay

with two lines

so Fairchild revised the prototype to

two rows of inline pins dual in-line

packaging or dip

introduced in 1965 the Simplicity of

dual inline packaging cut the cost of

assembly by a factor of four

the industry widely adopted it

throughout the 1970s and 80s during

those 20 years dips which include

ceramic and plastic versions held some

80 to 90 percent market share when

measured by value

however as the industry moved into the

1970s and the era of very large-scale

integration or vlsi demands for i o

density kept growing some vlsi chips

would require as many as 300 leads more

leads forced the dips to grow

increasingly large dips can have 64 or

even more leads but doing so gave them

impractically large board footprints

if Trends continued the way they were

the dip packages would end up being far

larger than the dyes themselves

this invalidates the various

miniaturization gains in semiconductor

Manufacturing

in response to this trend a series of

new packages capable of accommodating

far more leads emerged the packaging

industry's second big revolution

this generation of packages was defined

not by their shape but rather how they

were attached to the circuit board

surface mounting technology describes a

style of mounting packages onto the

board using flat patches of solder

already on the board

surface mounting had several advantages

over through-hole mounting first because

through-hole mounting required you to

solder the back side of the boards to

secure the dips you can only use one

side of the board with surface mounting

you can use both

this alone increases the theoretical

number of packages on a single board by

35 to 60 percent

second it allowed us to move the leads

closer together or in other words for a

smaller lead pitch this is because you

no longer have the solder contact areas

around the holes

and third you can use cheaper boards

drilling a hole into a board costs money

and there can be up to a thousand holes

on a standard board contemporary

estimates found that a surface mount

board costs 13 cents per square inch

while an insertion hole mounting board

costs 15 cents

furthermore the boards aren't peppered

with holes anymore which means they

don't need so many layers to maintain

their structural Integrity another cost

saving measure

previously all that surface mounting had

to be done by hand which considering the

smaller lead pitches required a great

deal of skill and training this was the

primary reason why surface mounting

didn't take off at first

new automatic machines finally closed

the loop on this manufacturers now use

convection heating hot gas or even

infrared heat Rays to solder the

packages onto the boards basically ovens

the origins of modern surface mounting

technology are murky and there isn't one

significant inventor or Eureka moment I

mean the concept of attaching stuff to a

board is not exactly groundbreaking

the earliest credible mention is a

British Patent filed in 1960. it

describes resistors coils and such

attached to a printed board using an

adhesive the connectors were connected

using solder

early adopters in the 1960s included the

U.S military which used flat packs for

their missile guidance computers the

flat pack was a stackable rectangular

glass and ceramic package that was

surface mounted onto a board

the flat pack was invented in 1962 by

Yong Tao of Texas Instruments so

actually a few years older than the

venerable dip I couldn't find much more

about inventor young Tao or his life

which is unfortunate

in the late 1960s the Swiss Watch

industry adopted surface mounting has a

way to reduce the number of electronics

in their watches

they popularize what is called the small

outline integrated circuit sometimes

also known as The Swiss outline

the small outline looks like the dip and

is made from the same molded plastic

materials however it is far smaller a

third is high and half as long this was

because as 28 Gull Wing leads are spaced

far closer together possible again

because we are directly mounting these

onto the board

they are called Gull Wing leads because

their shape is somewhat reminiscent of

seagull's wings

seagulls are birds that steal your hot

dogs at the beach

in the 1970s the Japanese electronics

Industry began adopting surface mounting

technology for their car radios tv

tuners and TV cameras it is likely they

got the idea from Europe Germany or

Britain perhaps

by the 1978 and 1980 period the

semiconductor packaging industry had

started moving towards surface mounting

with numerous published articles

discussing its use for increasing

packing density

in the early 1980s the Japanese revived

the old U.S military flat pack to create

an updated surface mount compatible

version called the quad flat package or

qfp

with the quad flat we have the leaves

projecting down and away from all four

sides of the square package

depending on their size the quad flat

can offer anywhere from 20 to 240 leads

pitches shrank to as small as 1 or 0.65

millimeters you can go guess how many

inches that is

the quad flat quickly evolved pushed

Along by consumer demands for smaller

and smaller consumer electronics the

Japanese Industries introduced yet

smaller packages like the shrink quad

flat package the very small quad flat

package and the thin quad flat package

on the other end of the spectrum new

structures outpace the quad flat on the

lead count front

people realize that having the leads

come out of the sides meant that you

couldn't use the real estate underneath

the package itself

so for high lead count devices the

packaging industry revived an old IBM

invention the pin grid array or the PGA

first introduced in 1971 the square

shaped pin grid array can handle

hundreds of leads on its Underside

IBM invented the pin grid array for high

i o uses in the computer industry those

packages were made from ceramic which

not only made them more expensive but

also their circuit boards since those

boards had to get thicker to handle the

added weight plastic variants were later

introduced

pin grid arrays were invented before the

surface mount Revolution so a surface

mount compatible cousin emerged in the

1980s the ball grid array

with these solder balls are used rather

than pins to connect the chip to the

circuit board one big disadvantage of

the ball grid was that you could not

easily visually inspect the solder

connections underneath the package

X-ray and electrical tests are often

used instead with badly soldered

packages removed re-balled and reapplied

solder ball technology appear in another

packaging Innovation that popularized at

about the same time as the BGA flip chip

this is where the Silicon dye is flipped

so that it faces downwards to build the

interconnects we ditch wire bonding

entirely and Connect using bumps and

balls on the Chip's pads

flip chip technology is still used today

and offers several benefits first there

is more contact with a heat sink which

dissipates more heat second electrical

signals have a shorter distance with

flip chip interconnects than Bond wires

starting in the 1990s consumers started

buying smaller Electronics like mobile

phones smaller devices mean smaller

components chips and packages space

became a premium in a chip package

the industry measures this using what is

called packaging efficiency the ratio of

the area occupied by the active device

the die

in response to this the packaging

industry developed the chip scale

package which entered the market in the

mid-1990s

chip scale packaging is an evolution of

the aforementioned ball grid array and

refers to any package where the bear die

occupies eighty percent or more of the

total package area

Taiwanese osat vendors like ASE group

rose up on the back of such Ultra

compact packages

one prominent implementation of this

concept is called wafer level packaging

this is where we hook up all the dye

interconnects before we cut those dies

out of the wafer it's not only very cost

effective but gives you very small

packages

as I mentioned earlier the Advent of

surface mounting technology created a

new generation of packages and

techniques has Moore's Law slows down

packaging technologies have seen yet

another surge of investment creating

what we can call Advanced packaging

Solutions

these new packaging Technologies now

have a much more direct role to play in

the system's overall performance

semi-analysis has a fantastic multi-part

breakdown on Advanced packaging that I

think drops the mic on the subject

perhaps the most well known of these are

chiplets this is a variant of what are

called multi-chip modules or hybrid

circuits or system in packages

I did a video about it previously most

prominently AMD used them to create a

disruptively great product

one special area of the multi-chip world

involves 2.5 D and 3D integration these

are especially cool

2.5 D integration is where we put

multiple dies side by side on top of an

interconnect substrate called a silicon

interposer this silicon interposer

doesn't have any logic but is just made

up of many embedded interconnects

there are a few consumer products using

2.5 D integration today for instance

amd's Radeon R9 Fury GPU first

introduced in 2015.

as a name implies 2.5 D is an

intermediate step towards 3D packaging

stacking and connecting multiple dies we

are now able to use a whole new

dimension to achieve packaging

efficiencies of over 100 percent

connecting these dies may require

something more heavy than your standard

wire bonds bringing forth New Concepts

like the through silicon Vias or tsvs

I am working on a future video on 3D

integration and die stacking so keep an

eye out for that if I ever finish it

the semiconductor packaging industry is

truly a chaotic one

there are so many different technology

trees growing concurrently with one

another each branch developing and

splitting for a certain significant need

new technologies are built on top of

those addressing particular Niche

applications and then suddenly before

you know it you have no idea why this

new thing which you saw fail a long time

ago is now such a big deal all over

again

in the semiconductor packaging World

ideas are created and then vanish off

the main line only to return to the

Forefront when their time is right love

it expect more deep dives into

semiconductor packaging in the near

future as we familiarize ourselves with

this new world

all right everyone that's it for tonight

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