Electronics > Beginners
Chip making process
Wimberleytech:
--- Quote ---Do foundries have a minimum wafer quantity. I mean wemberlytech showed cost of a wafer as USD 1600. So do the foundries expect you to order something like 100 wafers.
And if each wafer has 15000 dies on it. Do the foundries also charge you per die on that wafer.
I guess it should have been area based, if a wafer is 200mm in dia that comes to 31400mm^2. So Do they charge on area of silicon?
--- End quote ---
Foundry does not care how many die. They charge by the wafer.
ZeroResistance:
--- Quote from: Wimberleytech on October 16, 2018, 05:48:35 pm ---
To work with a foundry, you will have to commit to many thousands of wafers in production.
--- End quote ---
So did you have to commit for like 5000 wafers?
Richard Crowley:
--- Quote from: ZeroResistance on October 16, 2018, 04:00:10 pm ---Whats the problem in soldering the die directly to a pcb? are the bond pads too small that they can't be soldered directly to the board, similar to a LGA package? And then pour epoxy on it similar to a COB package. Like many chinese items have.
--- End quote ---
Depends on what you mean by "soldering". If you mean using a spool of solder and a soldering iron, forget it. You are off by a couple orders of magnitude. Your solder will cover 10-20 pads at a time. For "Chip-on-Board" (COB), they use the same microscopic bond-wire and ultrasonic welding that was used for decades for chip packages. Then they put a blob of epoxy over the whole thing to protect the die and bond-wires.
In more recent times a process called "flip-chip" is used where pyramids of solder are deposited on the bond-pads. Then the die is flipped over to face a PC board and the die and board are heated to re-flow the solder to connect all the pads to the board. In some cases, the raw die is left exposed. There are YouTube videos showing one of the flip-chips on the Raspberry Pi which turned out to be light-sensitive because it was unprotected and exposed to ambient light. People taking flash photos would inadvertently reset (or some other problem?) the circuit by the flash of light.
Modern CPUs are packaged this way. The CPU product is just a small PC board with the die bonded on top, and then a heat-spreader bonded on top of the chip. Frequently decoupling SMD capacitors are on the opposite "bottom" side of the CPU board to get them as close to the chip as possible. Then all the external connections are implemented with gold-plated pins (Pin-Grid-Array PGA) or lands (Land-Grid-Array LGA)
Wimberleytech:
--- Quote from: ZeroResistance on October 16, 2018, 06:01:12 pm ---
--- Quote from: Wimberleytech on October 16, 2018, 05:48:35 pm ---
To work with a foundry, you will have to commit to many thousands of wafers in production.
--- End quote ---
So did you have to commit for like 5000 wafers?
--- End quote ---
That is a detail I do not recall. I would think at least 1000 wafers/month. A foundry is in the speculation business. They will make a bet on your viability. If they believe in your business plan, they will be willing to do much smaller quantities while betting on the future large volumes.
jmelson:
--- Quote from: ZeroResistance on October 16, 2018, 05:11:33 am ---So what is the terminology is a reticle = a mask?
--- End quote ---
Way back when, the masks were made to expose the entire wafer in one shot. That worked up to 50 mm or so wafers. As wafers got bigger, and dimensions got smaller, they had to go from printing the whole wafer at once, to aligning a smaller reticle onto alignment marks on the wafer, and then step and repeat across the wafer. The process we have been using uses reticles about 35 mm wide.
So, today, a reticle has some number of chips that are aligned and imaged onto the wafer at one time. Then, the process is repeated across the wafer.
Jon
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version