Goo on calculator PCBs

G

Ghazan Haider

Guest
When I opened up a few calculators, and Commodore64 expansion
cartridges a long time ago, some PCBs have wires that converge into
what seems like a solidified drop of black plastic or ceramic. The
drop looks like it was liquid once upon a time, and is too hard to
remove, to check if there was an IC underneath or just silicon.
Apparently the object (IC or just silicon die) was placed on the PCB
connected to the wires, and the goo dropped on and solidified.

What is this process? Why dont they do this anymore?

And can home hobbyists do it?
 
On 19 Nov 2004 19:10:46 -0800, ghazan.haider@gmail.com (Ghazan Haider)
wrote:

When I opened up a few calculators, and Commodore64 expansion
cartridges a long time ago, some PCBs have wires that converge into
what seems like a solidified drop of black plastic or ceramic. The
drop looks like it was liquid once upon a time, and is too hard to
remove, to check if there was an IC underneath or just silicon.
Apparently the object (IC or just silicon die) was placed on the PCB
connected to the wires, and the goo dropped on and solidified.

What is this process? Why dont they do this anymore?

And can home hobbyists do it?
Click to expand...

Globtop. A bare IC die is epoxied to a PC board, wire-bonded to
traces, and a blob of epoxy is dumped on top. Calculators and cheap
toy-type things still do this a lot.

John
 
ghazan.haider@gmail.com (Ghazan Haider) wrote:

When I opened up a few calculators, and Commodore64 expansion
cartridges a long time ago, some PCBs have wires that converge into
what seems like a solidified drop of black plastic or ceramic. The
drop looks like it was liquid once upon a time, and is too hard to
remove, to check if there was an IC underneath or just silicon.
Apparently the object (IC or just silicon die) was placed on the PCB
connected to the wires, and the goo dropped on and solidified.
What is this process?
Click to expand...
That's epoxy over a bare die wirebonded to the board. Same technology
that's inside an IC, except the little wires go to the PWB instead of
the IC lead frame.

Why dont they do this anymore?
Click to expand...
Who says we don't dom it anymore?

And can home hobbyists do it?
Click to expand...
I have a prototype-quantity wirebonder in my lab, but it was quite
expensive, Far better to use ICs until you reach the point where
you are prototyping something that you will make 100,000/day of.
 
"Ghazan Haider" <ghazan.haider@gmail.com> wrote in message
news:1ad1e8b9.0411191910.34f6f13@posting.google.com...
When I opened up a few calculators, and Commodore64 expansion
cartridges a long time ago, some PCBs have wires that converge into
what seems like a solidified drop of black plastic or ceramic. The
drop looks like it was liquid once upon a time, and is too hard to
remove, to check if there was an IC underneath or just silicon.
Apparently the object (IC or just silicon die) was placed on the PCB
connected to the wires, and the goo dropped on and solidified.

What is this process? Why dont they do this anymore?

And can home hobbyists do it?
Click to expand...
They're still using it.
I've been looking for a bottle of that special Pitch for a long while. Would
make life a lot easier :)
regards
john
 
Thanks everyone for the answers.

It does raise another question. How much cheaper is a die compared to
a package, and who sells dies anyway beside Intel (OK 2 questions.)

Most MCU manufacturers only sell in standard packaging. Can I get the
picmicro, the avr, xilinx spartan, AMD Geode and ARM MCUs in die
format?
 
Ghazan Haider wrote:
Thanks everyone for the answers.

It does raise another question. How much cheaper is a die
compared to a package,
Click to expand...
A lot cheaper when you are paying less than a dime per uP
and you are buying 100,000 every day.

and who sells dies anyway beside Intel
Click to expand...
Nobody at the low end buys Intel. Way too expensive. Asian vendors
such as Winbond, Sunplus. EMC/Elan and Sonix own that market.
Be prepared for minimum orders of 50,000 and up with masked ROM,
long lead times, data sheets in Chinese, buggy DOS-based tools,
chips that don't work as advertised, and no support.

Most MCU manufacturers only sell in standard packaging.
Click to expand...
Really? News to me.

Can I get the picmicro, the avr, xilinx spartan, AMD Geode and
ARM MCUs in die format?
Click to expand...
Put in a standing order for 100,00 per day and any manufacturer
will sell you bare die parts. Hobby quantities? Go pound sand.

BTW, if you are in the market for 87 metric tons of
Jar Jar Binks dolls, I can get you a *great* deal... :)
 
On Sun, 21 Nov 2004 02:24:51 +0000, Guy Macon wrote:

BTW, if you are in the market for 87 metric tons of
Jar Jar Binks dolls, I can get you a *great* deal... :)
Click to expand...
http://www.google.com/search?&q=jar+jar+binks+must+die&btnG=Google+Search
--
The Pig Bladder From Uranus, still waiting for
some hot babe to ask what my favorite planet is.
 
John Larkin wrote:

On 19 Nov 2004 19:10:46 -0800, ghazan.haider@gmail.com (Ghazan Haider)
wrote:


When I opened up a few calculators, and Commodore64 expansion
cartridges a long time ago, some PCBs have wires that converge into
what seems like a solidified drop of black plastic or ceramic. The
drop looks like it was liquid once upon a time, and is too hard to
remove, to check if there was an IC underneath or just silicon.
Apparently the object (IC or just silicon die) was placed on the PCB
connected to the wires, and the goo dropped on and solidified.

What is this process? Why dont they do this anymore?

And can home hobbyists do it?



Globtop. A bare IC die is epoxied to a PC board, wire-bonded to
traces, and a blob of epoxy is dumped on top. Calculators and cheap
toy-type things still do this a lot.

John

-- and any home hobbiest with a wire-bonding machine and access to bare
Click to expand...
dice can do it (sorry, couldn't resist).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
This is called die-bonding (Wire bond-out also). The Goo is epoxy which
cures after being poured onto the board.

This is really cost effective when you are into production volumes of 50K+
per month (ie 0.5 Million units per year). The die Bonding machines weld
the wires onto the pads of the die and the PCB. The Goo (as you call it) is
then poured over the die (which also has some silica gel on to remove any
residual moisture) to stop the wires being deformed/shorted and to keep the
die dry. Oxygen [air bourne or water bourne] will oxidize parts of the
silicon and degrade it's perfomance/functioanlity/life.

Now you know!

If you are interested in doing this, please ask, I can put you in contact
with people who do this for a living!


"john jardine" <john@jjdesigns.fsnet.co.uk> wrote in message
news:cno1he$emf$1@newsg2.svr.pol.co.uk...
"Ghazan Haider" <ghazan.haider@gmail.com> wrote in message
news:1ad1e8b9.0411191910.34f6f13@posting.google.com...
When I opened up a few calculators, and Commodore64 expansion
cartridges a long time ago, some PCBs have wires that converge into
what seems like a solidified drop of black plastic or ceramic. The
drop looks like it was liquid once upon a time, and is too hard to
remove, to check if there was an IC underneath or just silicon.
Apparently the object (IC or just silicon die) was placed on the PCB
connected to the wires, and the goo dropped on and solidified.

What is this process? Why dont they do this anymore?

And can home hobbyists do it?

They're still using it.
I've been looking for a bottle of that special Pitch for a long while.
Would
make life a lot easier :)
regards
john
Click to expand...
 
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