Primoceler – Bonding the Future

Primoceler offers wafer scale and chip scale bonding to create reliable,
fully hermetic glass packages without heat or added materials.

Primoceler Glass Micro Bonding Technology – Permanent Hermetic Bonding

Glass – The Material of the Future

The use of glass wafers has increased over the past few years and the growth is expected to increase even more.

There are two types of traditional bonding methods, based on heat or on additive materials. Technologies based on additives can be, for example, adhesives, metallic coatings or absorbing layers. Additive materials cause outgassing. Also, issues with temperature changes are common. Furthermore, the gap between wafers is challenging to control. Poor gap control often leads to lower yield and a drop in device performance.

The second group is bonding methods based on heat. These include fusion bonding, anodic bonding and eutectic bonding. Heat based bonding are not suitable with heat sensitive MEMS components. Furthermore, many coatings are sensitive to heat. Organic coatings and thin film coatings, for example, can be damaged due to heat.

Hermetic optical sensor package
X

Hermeticity 100 %

7

Heat load (HAZ) 0 %

Primoceler has developed a new Glass Micro Bonding method based on laser technology.

The technology is suitable both for wafer level bonding and for chip scale bonding. Bonding is done without any additive materials and in room temperature.

Technology comparison is presented in the table below.

Primoceler glass micro bonding Fusion bonding Anodic bonding Adhesives or Additives
Hermeticity High High High Medium
Heat load Low High High Medium / low (UV)
Outgassing Low Low Medium High
Gap control High High High Low
Miniaturization possibility High High High Low
Other One step process Ultra high purity needed Conductivity needed Glue or other additives needed

Laser and glass bonding have intriguing possibilities for optical device packaging, as well as other applications in the hi-reliability markets. The process has already shown its potential effectiveness in solving problems for which there has never been a practical solution.

Liam Murphy

Hybrids and Packaging technologies, European Space Agency (ESA)

Bonding Principle

Perfect gap control

Primoceler glass bonding is done with a laser. Bonding is done at room temperature without any additive materials.

Bonding is done only at the material interface, and all surfaces are untouched. Top material needs to be transparent to visible light. Bottom material can be non-transparent, such as silicon.

Suitable materials:  Most glass types including Borofloat 33, D263T, fused silica, different types of quartz glass, soda lime and silicon.

Minimum bottom wafer / material thickness: 30 micrometers

Maximum bottom wafer / material thickness : 30 mm

Maximum top wafer / lid thickness: 3 mm

Minimum material thickness 30 micrometers

Example hermetic sensor package

Well proven technology – Reliability verification in extreme conditions

Primoceler’s bonding technology has been tested by third parties.

Furthermore, performance in extreme conditions for aerospace and for medical implant application has been verified.

An example device is presented in the picture on the left. The entire device package is manufactured from glass. Only the electrical feedthroughs and metallizations for die and wire bonding are non-glass. As the material selection in the package is kept minimal, issues due to temperature changes or outgassing are avoided.

The same principle can be used to design and manufacture using a silicon base. In this case the base plate is replaced with silicon. Interface to the PCB can be designed according to customer specification. In addition to ball grid array (BGA) other types of interfaces are possible. For example, a leadless chip carrier (LCC) -type of interface.

Example device – Process and reliability verification

Shar strength comparison

Shear force testing

The chart describes shear force strength comparison between Primoceler’s Glass micro Bonding and UV cured adhesive bonding.

Glue used in the experiment was Vitralit 7256, which is often used in glass to glass bonding.

The shear force test was done according to MIL STD-883, method 2019.7 at Technical Research Center of Finland (VTT).

 

Test method Conditions Visual
inspection
Device performance
Temperature cycling MIL-STD-750, Method 1051.1
-55oC…+175oC
100 cycles
Passed Passed
Moisture resistance MIL-STD-750, Method 1021
Temperatures: 65oC, 25oC, -10oC
Humidity 80-100 Rh%
Cycle duration 24h
Total number of cycles 10
Passed Passed
Solderability and temperature cycling SnPb solder
-55oC…+150oC, 100 cycles
Passed Passed
Hermeticity Set rejection limit for fine leak 6,0x10-12atmcm3/s Kr-85 Passed Passed

Reliability verification using MIL testing

The unique bonding technology has been tested using MIL standard testing methods. A review on tests performed is presented on the left.

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