Wire bond or flip-chip? Package types in two cross-sections.

The die is the same. How it meets the outside world changes the line, the materials and the skills an assembly plant needs.

In brief
  • Wire bonding connects pads on the die’s edge with fine wire loops.
  • Flip-chip turns the die over and connects its whole face through bumps.
  • Flip-chip allows more connections and shorter paths, at more process cost.
  • Each needs different equipment, materials and technician skills.
WIRE-BONDED · LEADFRAMEFLIP-CHIP · BALL GRID ARRAY123456789
  1. 1Die. Face up, connected from its top edge.
  2. 2Die pad and attach. Metal pad and adhesive that hold the die.
  3. 3Bond wires. Fine gold or copper loops to the leads.
  4. 4Leads. Part of the leadframe; soldered to the board.
  5. 5Mold compound. Seals and protects everything inside.
  6. 6Flipped die. Face down, connected across its whole area.
  7. 7Bumps and underfill. Solder or copper bumps, with underfill around them.
  8. 8Substrate. A small circuit board that routes the signals.
  9. 9Solder balls. The grid that connects the package to the board.
Fig. 01Two packages in cross-section, not to scale.

Side by side

 Wire bondFlip-chip
Die orientationFace upFace down
ConnectionsAround the edge onlyAcross the whole face
CarrierUsually a leadframeUsually a laminate substrate
Extra stepsWire bondingWafer bumping, reflow, underfill
Typical usesMany mature, cost-sensitive devicesProcessors and high-pin-count devices
Key skillsBonder set-up, loop control, pull testsBump, reflow and underfill process control

The line around the package

Whichever connection is used, the same back-end stations surround it.

  1. 01Grind and diceThe wafer is thinned and cut into dies.
  2. 02Die attachGood dies are fixed to a frame or substrate.
  3. 03InterconnectWire bonds or bumps make the connections.
  4. 04MoldThe assembly is sealed in compound.
  5. 05Final testEach packaged part is tested, some after burn-in.
  6. 06Mark and shipMarked, inspected, packed, shipped.
Fig. 02The back-end line. Interconnect is the station where wire bond and flip-chip differ.

Planning an OSAT or ATMP line means planning people for each of these stations. See Fab, OSAT and ATMP ramp, or the broader explainer.

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