Application Notes

* Requirement on surface metallization : both the substrate and device surfaces need be either silver or gold for strong bonding strength.
** Shelf life : 6 months (estimated) in a sealed container at room temperature, longer if stored in a refrigerator.

I. PRESSURE-LESS PROCESS (for devices smaller than 5 mm x 5 mm):

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 1.5 and 2.5 mil;
3. Place a device on the printed silver film and wiggle/slide 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.
4. On the right are recommended heating profiles for bonding devices to substrates with either silver-coated or gold coated surfaces.

II. PROCESS WITH LOW-PRESSURE (for larger devices):

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 4 mil (100 micron);
3. Heat the substrate in open air from room temperature to 210˚ C over a time of about 10 minutes and hold at the temperature for about 10 - 15 minutes until the paste film turns light color;
4. Place a device on top of the dried paste film, apply a pressure of 4 - 6 MPa in a hot press, and then heat up to sinter at around 250˚ C for 5 minutes if silver is the metal on the bonding surfaces of both substrate and device.   The sintering temperature may need to be raised by 10 to 20˚ C if gold is the metal on both bonding surfaces.  
5. Cool down to room temperature.   See graphic representation of the heating profile on the
   right.