Wafer-Level Packaging

Wafer level packaging (WLP) is a highly parallel process for the hermetical housing of micro mechanical and micro optical components. Based on our longtime experience in this field we offer a WLP “off the shelf” concept, from design up to pilot production. A technology transfer to high volume foundries is an additional option. This concept guarantees the advantages of cost reduction and risk minimization for the customer.

The housing of micro components at wafer level uses the precision of semiconductor and micro system technologies. The assemblies are constructed to be robust and extremely compact. The main focus is on the hermetic encapsulation of micro sensors and actuators as well as micro optical modules using various joining technologies such as glass solder or metals. There can be manufactured housings with optical transparent window surfaces for the visible area up to far infrared for micro optical modules.

The verification of the inner pressure in a wafer level package can be a stringent demand to estimate the expectable lifetime of a product. To date, there is no generally usable method for a cheap and sufficiently precise application to all kinds of MEMS. However, for resonant structures, ISIT has developed the "Neon ultra-fine leak test" based on measuring the Q-factor of an electromechanical oscillator (dampening effect of the enclosed gases), which allows to detect extremely small leak rates and to forecast the pressure increase over a product's lifetime. (Semi Guideline 4446 "Evaluating Hermeticity of MEMS Packages").

To maintain a vacuum in a very small package, outgassing and desorption of gas molecules from the inner surfaces has to be controlled. So-called "getter" films allow to absorb free molecules of the most frequently found gas species, like an in-situ pump that remains active through the whole lifetime of a product.