Chip-on-board glossary
Short definitions of the terms used across this site, in alphabetical order. Each links to the page that uses it.
- Backgrinding
- Thinning a wafer from the back before dicing, when the die must be thinner than the wafer. See wafer dicing and division.
- Ball bonding
- A wire bonding method that forms a ball at the end of the wire and presses it onto the pad, used with gold wire. Compare wedge bonding.
- Bond finger
- See PCB bond pad.
- Bond pad
- A pad a wire is bonded to. Die pads are on the die; PCB bond pads, also called bond fingers, are on the board. See bond pads and pitch.
- Bonding diagram
- A drawing of the die on the board with a line for each wire from a die pad to a PCB pad. It tells the bonder which pad goes where.
- COB (chip-on-board)
- A bare die glued directly to a printed circuit board and wire-bonded to it, then covered with glob-top. There is no package. See chip-on-board bonding.
- Die
- The bare, unpackaged chip, cut from a wafer. The plural is die.
- Die attach
- Fixing the die to the board with adhesive, before wire bonding. The pad it sits on is the die attach pad.
- ENIG, ENEPIG
- Surface finishes for PCB pads: electroless nickel with immersion gold (ENIG), and with palladium added (ENEPIG). Both are suitable for wire bonding. HASL and OSP are not.
- ESD structure
- Protection circuitry on a die's pads. We use it to test signal pads: a small current through the structure shows whether the bond is connected. See how we test.
- Fiducial
- A copper mark on the working edge of a panel that the machine uses to locate it. At least two must stay visible after die attach.
- Film frame
- A frame holding dicing tape with singulated die on it. One of the ways die can be supplied. See supplying your die.
- Glob-top
- The epoxy dome over the die and its wires. Ours is hard AB epoxy, clear or black.
- Jig
- The metal fixture that holds boards or panels on a bonding machine. Fit and dimensions depend on the partner and process; review the panel before ordering.
- KGD (known-good die)
- Bare die tested at wafer level and sold as working. See known-good die sourcing.
- Mil
- One thousandth of an inch, 25.4 µm. Wire diameter is often given in mils: 1.0 mil is 25.4 µm.
- MPW, shuttle
- A multi-project wafer run, where many designs share one wafer to share the cost. Tiny Tapeout and wafer.space run shuttles.
- Open
- A fault where a wire does not connect the die pad to the board pad. One of three faults we test for.
- Panel
- Several boards joined into one PCB and separated after assembly. See arranging boards into a panel.
- Pitch
- The distance from the centre of one pad to the centre of the next.
- Pin 1
- The reference pad that defines the orientation of a die. Mark it on the pad map and the bonding diagram.
- Short to ground
- A fault where a wire or pad touches ground when it should not.
- Short to neighbour
- A fault where two adjacent wires touch each other.
- Singulation, dicing
- Cutting a wafer into individual die.
- Slot size
- The die size on a wafer.space shuttle: 1 x 1, 1 x 0.5, 0.5 x 1 or 0.5 x 0.5.
- Tape and reel
- Die in the pockets of carrier tape wound on a reel. See supplying your die.
- Waffle pack
- A tray with one pocket per die. Our standard supply format.
- Wedge bonding
- A wire bonding method that presses the wire flat under a wedge-shaped tool, used with aluminium wire. It is our standard, at 1.0 mil. Compare ball bonding.
- Working edge
- A component-free strip along two opposite edges of a board or panel that the machine holds. Also called a rail. It carries the tooling holes and fiducials.