Packaged Integrated Circuit Manufacturing

We are specialists at hermetic sealing using projection welding. Many hermetic sealing technologies are not compatible with FR4 and other organics because they involve the use of elevated temperature. With projection welding, the elevated temperature is so fast and localized that internal components are not affected. You can learn more on http://mysite.verizon.net/tom.es. Alternately, you can do a google search under hermetric and read some of our papers.

I am working on the process to alter the design to ceramic substrate of Alumina. I will also consider laser welding using short pulses to seal without heating the module.

Projection welding works well, regardless of substrate material. Alumina is better than FR4 because it doesn't absorb water vapor and it has better thermal properties. Laser sealing works, but is expensive and slow compared to projection welding. Depending on the size of packages, projection welding can seal 100 -500 parts per hour - more if automated.

You are using spot welding and perhaps may be OK for some parts you are doing. I will prefer either 1550nm fiber optic welding in 1ns to 100ns pulses to get desired welding. I have other options also. I will like to own this set up. I can make one.

Our experience indicates that certain amount of energy is required to heat materials for soldering, brazing, welding, etc. The required energy can be delivered at low power for longer time or high power for shorter time. In the limiting cases, one has isothermal heating and perfectly adiabatic heating (vaporization). The heating time you propose (1.0 - 100ns) is good for marking and engraving materials because it ablates the target material away. For joining applications we prefer wider heating pulses in the 1 - 10 ms range. This gives energy time to diffuse into materials to create bulk heating instead of superficial ablation. Our technology is based on projection welding which is a variant of spot welding. The entire seal perimeter is welded with a single pulse. It is much faster than laser welding where the joint is made by a series of overlapping pulses to form a continuous seam.

Laser pulses are 100ns range and also hit micron size area that easily melts and flows. It is fine quality welding and not a gross welding which needs a lot of material flow. Basically seam is welded and not to large depth. This is an specialized area and not applicable all types of laser welding applications.