The acronyms 3D IC, TSV and TCB represent 3 Dimensional Integrated Circuit, Through Silicon Via and Thermocompression Bonding, respectfully.
Fundamentally, 3D IC, TSV, TCB all fall under one basic category, TCB, along with many other bonding processes and packaging types. For example, Flip Chip C4 and all its variations, 2.5D IC, Direct Chip Connection, GGI and the list goes on....Which begs the basic question what does all these bonding processes have in common? They are all level one packages/processes where the bare components establish interconnections directly to the substrate via temperature, bond force and time.
There is much written on this general topic but for the context of this write-up we will draw a further distinction of TCB, mass reflow vs in-situ bonding. For example, TCB of a C4 bump process (Controlled Collapse Chip Connection) can be established by applying tacky flux to temporarily hold the die in place while the substrate/die is past into a reflow oven where the C4 solder bumps are passively melted in a mass reflow configuration. Comparing the mass reflow process to an in-situ bonding process where the die is held in place accurately, bump to interconnect pad, while heat and bond force is dynamically applied until the solder is melted and cooled establishing the bonded interconnect.
An in-situ TCB process is typically employed when the bonding process dictates this technique or when placement accuracy is paramount to the success of the interconnect process. For example, when stacking TSV die with micro sized bump diameters requires an in-situ bonding process, a mass reflow process would not be practical or even feasible with today’s TSV processes. As another example, mass reflow would not be very effective when bonding Flip Chip die using a non-conductive film (NCF) or non-conductive paste (NCP) process, here again, one would integrate in-situ bonding while applying dynamic heat and force as part of the bonding process.
A C2 bump interconnect process (Chip Connection) is typically a copper pillar capped with an AgSn platting. C2 is basically a hard bump were the bump will not collapse like the typical C4 solder bump. The C2 bump configuration allows tighter bump pitches and small bump diameters therefore being ideal for very high density I/O devices. Here an in-situ bonding technique is used, the die can be aligned and held in place while bond force and temperature is applied until all interconnections have been established and then the bondhead is released from the die maintaining the all too critical placement accuracy. In this example ±3.0μm @ 3σ placement accuracy is required, noting that the placement accuracy is primarily dependent on the bump pitch and bump diameter of the package.
AMICRA offers two die attach solutions to address the TCB market segment. We primarily serve the high volume production segment of the TCB market.
AFC Plus supports:
- Die placement accuracies down to ±0.5μm @ 3σ with cycle times down to 20 to 30 seconds/bond or 180 to 120 UPH
NOVA Plus supports:
- Die placement accuracies down to ±1.5μm @ 3σ with cycle times down to 3 seconds/bond or 1,200 UPH
A capacity/bulk of materials like die or lenses and substrates can be manually loaded or automatically presented to the AMICRA system. The die or lens can be presented to the machine in waffle packs, gel packs or wafers (film frames or grip rings). The substrates can be presented to the machine one at a time or in custom trays, or the AMICRA system can load each substrate to the bonding stage automatically, provided the substrates are presented in wafer, waffle packs or gel packs.
Epoxy or UV adhesive can be applied to the die via die dipping or applied via pin transfer (epoxy stamping) or via through a variety of standard dispensing systems, located at the bond station or located upstream prior to the bond station:
- Time Pressure Vacuum Dispenser
- Volumetric/Auger Dispenser
- Jet Dispenser
Note: The AMICRA systems are essentially a vision driven die attach machine consisting of 4x automatic vision systems located throughout the machine, all imaging systems (camera, optics and illumination) are fixed to a very rigid structure made of granite. Imaging systems are located:
- Pick-up Station with a precision X-Y Table
- Mapping/Alignment Station consisting of an upward looking camera and a downward looking camera
- Bond Station with a precision X-Y Table
A single or dual pick and place bondhead(s) are mounted to a linear motor where either a die, lens or flip chip die are picked up, via a vacuum tool, from the Pick-up Station and either the:
- Die are transported to the Mapping/Alignment Station for alignment then moved to the Bond Station where the die is bonded to epoxy
- Lenses are transferred to the Bond Station where they are placed into the UV adhesive while UV light is projected on to the Lens until the adhesive is cured and bonded.
- Flip chip die or laser die, p-side down, is transferred to the Mapping/Alignment Station where the bumps or critical alignment features of the die are mapped to a feature on the backside of the die, i.e. the die corner for alignment and finally, the die is transferred to the Bond Station where laser heat is applied to the substrate or silicon wafer, while the die is being eutectically bonded in-situ while maintaining the required placement accuracy.
Additional Key Features, Options and Capabilities
- Dynamic Alignment with 3x levels of Post Bond Inspection
- Flip Chip System
- HEPA Filter with Ionizer
- Heated Bond Tool
- Laser Soldering System
- Pulse Heater
- Wafer Heater
- Wafer Substrate Loader & FOUP Loader
- Substrate Magazine Loader
- Active Bond Force
- Supports 300mm Wafers and Large Substrates up to 550mm x 600mm
- Bonding Resolutions <0.1μm
- Autocollimator for Parallelism Calibration