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Die package

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Marks256

New Member
I'm just curious as to how die packaging works (the little blobs of epoxy coated circuitry.)

I know the die is just made on the circuit board, but how does that work? If a company orders a chip, how is the die shipped? or is it placed on the circuit board at the manufacture of the die chip?

For example, you know all those cheap Chinese circuit boards that cannot be (easily) hacked, how do those Chinese manufactures get the boards? Do they solder the packages down themselves, or do they have the manufacture of the chip place the die package on?

Thanks :)
 

dknguyen

Well-Known Member
Most Helpful Member
THe blobs of epoxy? I always thought it was just a regular IC and then put a blob of epoxy over it.
 

jpanhalt

Well-Known Member
Most Helpful Member
Look up chip-on-board. Here's a decent description: Chip-on-Board (COB); Direct Chip Attachment (DCA)

Unfortunately, it doesn't go into much detail about the how to and where part of the question. It does confirm that it is the die itself, not a completed IC that is attacheded to the board.

John
 
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duffy

Well-Known Member
They get the dice from the manufacturer and use a wirebonding machine to attach it. There are people in China with wirebonding machines in their basements. Grandma brings in a tray of dice wearing footies and a hair-net, the kids run the die-bonder, dad is on the phone making deals. Common die forms like LED's are a standard part number with mechanical specs and packaging information, but many other chips can be ordered this way.
 

Speakerguy

Active Member
Good lord, I've never seen that before. They've got to have that process automated. I've done wire bonding manually (or rather I have 18 hours of training on a K&S manual wirebonder). It's difficult to say the least.
 

Hayato

Member
They get the dice from the manufacturer and use a wirebonding machine to attach it. There are people in China with wirebonding machines in their basements. Grandma brings in a tray of dice wearing footies and a hair-net, the kids run the die-bonder, dad is on the phone making deals. Common die forms like LED's are a standard part number with mechanical specs and packaging information, but many other chips can be ordered this way.

Good description. :D

I have a 1 Mbit EEPROM die here. It is 3mm x 1.5 mm.
 

Marks256

New Member
Aaah. ok... So, hypothetically - if i were a company, and wanted to have a COB (Chip-on-Board) component on my circuit board (to cut costs), how would that work? Because i could not do it myself, so who would have to do it for me?
 

duffy

Well-Known Member
Just type "die bonding" into Google.
 

Marks256

New Member
Right i understand WHAT is done, but how one GET it done? I am sure not every company that has a die on their product owns the equipment to set the die, so where do they go to get it done?
 

duffy

Well-Known Member
That's what I'm telling you - these are third-party services. The die manufacturer sends them the dice, you send them the boards, they bond it and blob-top it.
 

Marks256

New Member
Ok, i get it now! Thank you. :)

So, one company makes a board, another company does the die (the chip manufacture), and both of those are shipped to a third party company which will place the die on the board, and bond/blob it?

haha, i don't see why i wouldn't have thought of that :) Thank you much duffy. ;)

So what are some example companies to do this? Say if futurlec did the PCBs, Microchip did the die, then who would do the die job?
 

duffy

Well-Known Member
>>who would do the die job?

Call it "die bonding", they will respect you more. The first page of Google shows a company called CIL that die bonds to FR4. We used a couple of places in China and Hong Kong when I worked for Rehkemper, but I don't remember the names. We used "Winbond" microcontrollers, which are very popular for this application in asia for some reason.
 

Marks256

New Member
Die bonding? ok. :) It's about time i start getting some of this terminology down.

Thanks :)

i'm sure i'll have more questions soon ;)
 

Marks256

New Member
So what is the proper term for the finished product? The die, epoxy, everything.
 

duffy

Well-Known Member
A "COB assembly" (chip on board) - not to be confused with a COG assembly, which used to be on glass, except now it's usually a flip-chip on a flexible pc board, and more properly called a COF.

Which brings up another point - flip-chips (also called "solder bumped") versions of the same die are the new thing. The advantage is they don't need wire bonding, the soldering process is compatible with the conventional SMT soldering. They can't handle much power, though, and they still have to be encapsulated (blob topped, glob topped).

Another disadvantage is that you don't have as much freedom in your layout. With down bonding to a pcb substrate you can use the "bond length" skip over traces near the chip.

A die is sometimes called a bare die - contact the manufacturer for the chip you want to use and ask if you can buy the bare die and ask if they make a flip-chip version of it. With some chips and some manufacturers you won't have the option for any of this. With other manufacturers and other chips (like Atmel T5557) not only will they sell you the dice, they will sell you the whole damn wafer (tested, marked) and you can saw the chips out of it yourself if you want to.

You would probably want the dice delivered in a "waffle pack" (looks like a waffle) to the guys doing the die bonding. The die bonding guys may want to etch the boards themselves, otherwise they have to do plasma cleaning to get rid of surface contaminants. The Chinese in the basement are using Feng shui and Chi energy to keep those surface contaminants at bay.

The the die and bonding wires attach to the PCB. The bonding pads on the PCB have to be plated. The plating depends on the wire. The wire depends on the chip. It's either going to be gold or aluminum. If it's gold, the plating on the pc board pads is a heavy layer of bondable gold. If it's aluminum, it's a thin layer of bondable gold over bondable nickle. Gold's more expensive but more flexible and reliable. Aluminum can get something called "puple death" or something - don't look that up, I can't remember WTF it is, but the aluminum gets into the gold and wrecks it. So we always used aluminum. There's something called peg bonding and wedge bonding and ball bonding - let the die bonder guys deal with that. Basically they all slam the wire against the metal really hard and it welds itself on there.
 
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Marks256

New Member
Ok, i just looked up Flip-chip Assembly, and it looks as if that would be somewhat cheaper?
 

duffy

Well-Known Member
Seems like it ought to be. You flux it, place it upside-down on the solder-paste screened boards, reflow it along with the SMT's, clean it, underfill it, and encapsulate it. No wires, no gold, ought to be quicker and less expensive.
 

Marks256

New Member
What do you mean by cheaper... What's your budget, quantity?

Well i'm just toying with an idea for now, and want to make sure i can do it (hence all the questions). But i am really nervous about going into this, as i am going in blind (don't really know much about business :s)

I was thinking about 20 boards being made initially. The boards would be approximately 3cm by 4cm. Each board would consist of a single chip on it (hoping to have a COB), and a few discreet components. I do not have a set budget at this time. I would like to keep it under 400 for the entire product. After a little guesstimating, it does seem possible to stay within this budget for 20 units.


On that note, does anyone know of any good reading on how business works? More specifically, from the idea process to the product? Steps to take in between, things to do (patents if needed), licensing, contacting manufactures, and how to be more or less "professional" about it all. I am not expecting a miracle, but i want to have a loose idea of what is going on.

I know my idea isn't going to be the next big thing, but i like the idea, and it will bring some extra spending money. I know i haven't mentioned what the idea is, for fear of it being taken. Maybe i am just being paranoid and/or ignorant. But that is why i was wondering about a book, or any asset to help me learn what i should be careful of, how much i can say, to whom i can say it...

i hope you all don't think i'm crazy. :)

And thank you all very much for your help. :)
 
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duffy

Well-Known Member
Volume's way too low. You do direct bonding for quantities of 100k and up, otherwise it doesn't pay. You are saving money on the lead frame processing, basically.

That board's plenty big for even a big chip, why do you need an exotic assembly technology?
 
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