Optical Package Assembly

Optical packages are basically assemblies comprising optical (lenses, prisms, apertures, filters, etc.) and electronic components (LD, PD, amplifiers, controllers, etc.). Typical fields of application 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 get the idea, 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

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

  • 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

  • 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

  • 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

  1. Place preform on package bottom
  2. Place TEC on preform
  3. Solder with Forming Gas

Process Step III: Bond Sub Assembly on TEC

  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

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

Integrated Process Management (IPM)

  • Integrated Process Management (IPM)
  • Principle of process gas integration
  • Operating software for bonding

The Integrated Process Management (IPM) is the center piece of a FINEPLACER® system1 - the place where it all comes together. IPM is more than just thermal management. It synchronizes the control of all process modules and their related parameters:

  • Controlled and precisely balanced interaction of top and bottom (pre-)heating and cooling
  • Control of temperature, time, force, power, energy, flow
  • Controlled process gas integration for reduced solder contamination, minimized surface tension effects and smooth spherical solder residues

 IPM is very complex, yet easy to access. Via the GUI of the operating software, the user has perfect control of all required adjustments. Just drag 'n drop to define temperature ramps or activate process modules. All settings are represented in only one profile, making for a very intuitive work flow.
 
The operating software provides an ever-growing library of profiles for all kinds of processes. It also offers comprehensive data logging functions essential for statistical process control.

In combination with the system-to-system process transfer capability this is as easy as process development can get.

1 FINEPLACER® core offers co-ordinated top and bottom heating but does not support IPM

Recommended Bonding Systems

  • FINEPLACER® femto
    Automated sub-micron die bonder
  • FINEPLACER® matrix ma
    Semi-automated die bonder
  • FINEPLACER® lambda
    Flexible sub-micron die bonder
  • FINEPLACER® pico ma
    Multi-purpose die bonder
  • FINEPLACER® pico ama
    Automated flip chip bonder

FINEPLACER® bonding systems essentially vary in

  • 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.