Applications

NBE’s nanoTach® pastes are targeted at joining semiconductor chips for high-performance, high-reliability, and high junction-temperature applications, such as power electronics, automotive electronics, concentrated photovoltaics, high-power light-emitting diodes (LEDs) or high-power laser diodes, and high-power, compact communication systems.

Recommended Heating Profiles

* Requirement on surface metallization: both the substrate and chip surfaces need be either silver or gold for strong bonding strength.

A. ZERO PRESSURE PROCESS (for chips smaller than 3 mm x 3 mm) with nanoTach®-N paste:

  1. Use a metal rod (e.g. a paper clip) to mix well the paste if it has been in storage for some time.
  2. Print the paste onto substrate using a stencil or a spacer to a thickness between 1.0 and 2.0 mil. It is important to make sure that the paste material wets, i.e. makes complete and close contact, with the entire substrate surface.
  3. Place a chip on the printed silver film and wiggle/slide/scrub the device while pressing lightly to ensure good contact of the device surface with the wet silver; note: too much pressure should be avoided since it will make the Ag layer too thin for strong bonding. An ideal bond-line thickness before heating is between 30 and 50 microns.
  4. Below is a recommended heating profile for bonding chips to substrates with either silver-coated or gold coated surfaces. Leaving the assembled parts in the ambient for several hours or overnight prior to heating can significantly improve bonding strength.

B. PROCESS WITH LOW-PRESSURE (for larger chips) with nanoTach®-K paste:

  1. Use a metal rod (e.g. a paper clip) to mix well the paste if it has been in storage for some time;
  2. Print the paste onto substrate using a stencil or a spacer to a thickness of about 2.0 to 4.0 mils;
  3. Heat the substrate in open air to 150oC at a ramp rate of 10oC/min and soak for 5 to 10 minutes.
  4. Apply (by printing or dispensing) a thin (about 5 to 10 microns) fresh layer of the paste on the dried print, place a chip on top of the wet print, and follow the heating profile shown above. At 125oC, start applying pressure of 2 - 5 MPa on the chip and maintain that pressure throughout the sintering process.