Wafer Level Processing

WLP: Wafer Bumping, Wafer Level CSP & Bare Die Processing

STATS ChipPAC’s Wafer Level Processing (WLP) services include full service wafer bumping with options for wafer repassivation, redistribution and IPD layers with polyimide dielectric with the solder alloy selection flexibility of a printed paste solder bump technology. This internal wafer bumping capability enables full turnkey Flip Chip-in-Package assembly and test. For larger pitch applications, either printed paste bumping or mechanical ball drop are available. Additionally, a complete, flexible backend assembly capability allows for high volume wafer sorting, automatic optical inspection and backend processing into bare die in tape and reel or waffle pack for Flip Chip-on-Board applications by the end user.

WLP Features

  • In-house thin film on wafer processing and bumping of 6" and 8" wafers
  • Optional repassivation or redistribution with Polyimide dielectric material
  • Wafer level IPD and thick copper (8-12um) conductors available
  • Bump offering supports STATS ChipPAC’s internal Flip Chip-in-Package product offerings, bumped bare die and wafer level chip scale packages (WLCSP) for Flip Chip-on-Board applications
  • Bumps formed by printed paste bumping technologies or direct ball drop
  • Minimum available flip chip bump pitch of 150um using printed paste
  • Large bump (250-500um) processing at 0.40mm pitch and greater for Flip Chip-on-Board and WLCSP applications
  • Eutectic (standard and ultra-low Alpha); Pb-free (95.5Sn/4.0Ag/0.5Cu, 96.5Sn/3.0Ag/0.5Cu or 98.5Sn/1.0Ag/0.5Cu); solder alloys available
  • 0.3mm minimum bumped die height; die heights between 0.40 and 0.80mm are common
  • Flexible bare die processing capability including wafer thinning, laser marking, automated optical inspection and electronic mapping, pre- and/or post-bump wafer probing and die sorting and picking into either tape and reel or waffle pack formats
  • Underfilling of substrate mounted bumped die may or may not be required depending on the customer’s specific application and reliability requirements
  • Underfilling by overmolding feasible

WLP Market Applications & Drivers

  • STATS ChipPAC’s WLP service enables full service low-end through high-end Flip Chip-in-Package solutions for wireless, portable products as well as high-end networking and computing applications.
  • Alternatively, on the lower end, bumped bare die are targeted towards electrically enhanced, form factor sensitive and lower I/O applications primarily within the wireless and portable product space.