Optical Package Assembly

The flexibility built into Finetech die bonders is ideal for the variety of process technologies required in optical package assembly.  Optical packages are assemblies comprising optical (lenses, prisms, apertures, filters, etc.) and electronic components (LD, PD, amplifiers, controllers, etc.). Applications can be found in communication technologies where optical signals are transformed into electrical signals and vice versa. In order to have a package working properly it is mandatory that the optical and electronic parts are aligned to each other with highest precision. The task becomes even more complex as, by design, these packages typically are actively tempered by thermo-electric coolers (TEC), which need to be integrated into the assembly as well.

To illustrate, a multi-step application of bringing a lense into a TOSA using several bonding technologies (gluing, soldering, thermocompression) is described below.

A lense on a silicon submount is placed into a V groove in a defined distance to the outlet facet of a semiconductor laser. The silicon submount is seated on a TEC and the TEC is integrated into the TOSA. Finally, a flex contact is bonded onto the TOSA insert to connect the circuit to peripheral devices.

  • Precision lens placement into a V groove
    Precision lens placement into a V groove

What are the Challenges?

  • Multiple step task
  • Accuracy better than 5 microns
  • Sophisticated tooling
  • Various lighting and magnification values
  • Relative placement
  • Different planes of sharpness
  • Different processes (gluing, fluxless lead free soldering, thermocompression)
  • Different process parameters (temperatures, time, force)

The Finetech Solution

Example: TOSA/ROSA

  • Typical Transmitter Optical Sub Assembly (TOSA) design
    TOSA outline and specs
  • TOSA component parts

A typical TOSA (Transmitter Optical Sub Assembly) design:

  • Hermetic case, ultra compact
    • Kovar body with CuW bottom
    • Contains  LD, monitor PD, electronics, thermo-electric cooler (TEC), filters, lenses
    • Fibre connection and lens on front
    • Electrical RF connection on back side
  • For Ethernet connections up to 100 Gbit/s
    • TOSA: Transmitter Optical Subassembly
    • ROSA: Receiver Optical Subassembly

Typical Process Steps

  • bond lens to TOSA/ROSA process steps
    Lens to silicon submount
  • Silicon submount to TEC
  • TEC to bottom of TOSA
  • Flex contact to TOSA insert (the ceramic contact strip)

I. Bond lens on silicon submount (Adhesive bonding)

II: Bond TEC on bottom of package (Lead free soldering)

III. Bond silicon submount onto TEC (Lead free soldering)

IV. Bond flex contact on insert (Thermocompression bonding)

Process Step I: Adhesive Application and Defined Lense Placement

  • lens placement adhesive application
    Precise adhesive application into V groove
  • Specialized Finetech tooling
  • Align LD beam outlet to lens peak point
  • Micrometer screws with digital readout allow relative positioning of the lens against the ld
  • Lens placement into V groove
  • Holding the lens while bonding
  • Lens shortly before final placement into V groove
  • Alignment lens to laser outlet facet

Apply Adhesive Into V Groove

  1. Mix 2 compound epoxy adhesive
  2. Fill adhesive into tub
  3. Dip dispensing tool into adhesive
  4. Align dispensing tool to V groove
  5. Put down placement arm to dispense adhesive
  6. Lift placement arm for next process


Place Lens Into V Groove at Defined Position

  1. Pick up lens from tray in defined orientation
  2. Align LD beam outlet to lens peak point
  3. Shift substrate in x, relative to lens
  4. Place lens into V groove
  5. Cure adhesive by heat

Process Step II: Bond TEC on Bottom of Package

Bond thermo-electric cooler on package
  1. Place preform on package bottom
  2. Place TEC on preform
  3. Solder with Forming Gas

Process Step III: Bond Sub Assembly on TEC

Bond sub-assembly on thermo-electric cooler
  1. Place preform on TEC
  2. Align lens to package lens (x and y direction)
  3. Place subassembly on preform
  4. Solder with Forming Gas

Process Step IV: Bond Flex Contact on Insert

Bond Flex Contact on TOSA Insert
  1. Align contact zones (x and y direction)
  2. Bond flex contact on TOSA's insert using Thermocompression

FINEPLACER® Bonding Systems

  • FINEPLACER® femto
    Automated Prototype2Production Bonder
  • FINEPLACER® matrix ma
    Semi-automated die bonder
  • FINEPLACER® lambda
    Flexible sub-micron die bonder
  • FINEPLACER® pico ma
    Multi-purpose die bonder

Due to the modular design approach, FINEPLACER® bonding systems can be configured for virtually any application challenge.

The main distinguishing features between the machines are the

  • degree of automation
  • optical resolution and
  • placement accuracy

Browse our product range or get in contact with your sales contact to figure out the best equipment solution for your requirements.