Laser Sealed Packaging for Microsystems

Packaging is the last process of microsystem manufacturing. There are mainly two kinds of packages: plastic or metallic. The two main components of the package (base and cover) may either be glued or soldered. Each of these techniques has its advantages and drawbacks, and the choice should be driven by the functionality of the microsystem. The advantage of gluing is that it is quite an easy production process. The drawback is that glue, like all polymers, is not hermetic on the long term. This is a problem when the package should protect the microsystem from oxygen or water vapour, an example being OLED displays (Organic Light Emitting Diodes). The advantage of soldered metallic packages is that they are hermetic. The drawback is that the welding process takes place in an oven, and that the whole microsytem is heated to the fusion temperature of the joint. This is a problem for many microsystems, typically biomedical MEMS and OLEDS again. The LPM-EPFL is working on the development of a two-part sealed packaging. One part of the package is metallic, the other part is made of glass. The goal of the project is to soft solder the two parts of the package by the mean of a laser diode. The advantages of the laser soft soldered joint are : –its water and air-tightness in regard to glue or a plastic joint, –the possibility to heat only the solder joint, and not inside the package

The tobacco industry's past role in weight control related to smoking

Background: Smoking is thought to produce an appetite-suppressing effect by many smokers. Thus, the fear of body weight gain often outweighs the perception of health benefits associated with smoking cessation, particularly in adolescents. We examined whether the tobacco industry played a role in appetite and body weight control related to smoking and smoking cessation. Methods: We performed a systematic search within the archives of six major US and UK tobacco companies (American Tobacco, Philip Morris, RJ Reynolds, Lorillard, Brown & Williamson and British American Tobacco) that were Defendants in tobacco litigation settled in 1998. Findings are dated from 1949 to 1999. Results: The documents revealed the strategies planned and used by the industry to enhance effects of smoking on weight and appetite, mostly by chemical modifications of cigarettes contents. Appetite-suppressant molecules, such as tartaric acid and 2-acetylpyridine were added to some cigarettes. Conclusion: These tobacco companies played an active and not disclaimed role in the anti-appetite effects of smoking, at least in the past, by adding appetite-suppressant molecules into their cigarette

A Quantitative Method for Comparing Trajectories of Mobile Robots Using Point Distribution Models

The need for efficient security systems led to the development of automatic behavioral identification tools using video tracking. However, in the field of mobile robotics, trajectories are seldom taken into account to qualify robot behavior. Most metrics rely mainly on the time to accomplish a given task or on a prior knowledge of the robot controller, with the assumption that the trajectory can be kept within a maximal bounding error. A trajectory analysis method based on a Point Distribution Model (PDM) is presented here. The applicability of this method is demonstrated on the trajectories of a real differential-drive robot, endowed with two different controllers which lead to different patterns of motion. Results demonstrate that in the space of the PDM, the difference between the two controllers can be easily quantified. This method applies equally well to the trajectories gathered in real world experiments as to those generated in a corresponding realistic simulation. Quantitative comparison between these results (real and simulated) affords an assessment of the simulation quality, when simulation features are appropriately tuned

Laser soldered packaging hermeticity measurement using metallic conductor resistance

Packaging is the last step of the manufacturing process of Microsystems. The LPM is working on the development of a two-part soldered packaging. One part of the package is metallic; the other part is made of glass. The goal of the project is to solder the two parts of the package using a laser diode. The advantages of the laser soldered joint are its hermeticity to water and air in regard to glue and plastics, as well as the possibility to heat only the soldered joint, without affecting its contents. This work presents results of this packaging process, together with a method used to measure the hermeticity based on the oxidation of a heated metal conductor such as tungsten. The resistance of the conductor, which is encapsulated inside the package, increases as oxygen and water diffuse through the seal, which provides a convenient semi-quantitative measurement

Laser Soldered Packaging Hermeticity Measurement Using Metallic Conductor Resistance

Abstract: Packaging is the last step of the manufacturing process of Microsystems. The LPM is working on the development of a two-part soldered packaging. One part of the package is metallic; the other part is made of glass. The goal of the project is to solder the two parts of the package using a laser diode. The advantages of the laser soldered joint are its hermeticity to water and air in regard to glue and plastics, as well as the possibility to heat only the soldered joint, without affecting its contents. This work presents results of this packaging process, together with a method used to measure the hermeticity based on the oxidation of a heated metal conductor such as tungsten. The resistance of the conductor, which is encapsulated inside the package, increases as oxygen and water diffuse through the seal, which provides a convenient semi-quantitative measurement

Laser soldering of piezoelectric actuator with minimal thermal impact

Mechanical and electrical connecting of piezoelectric actuator is often done using conductive glue. Its advantage is not to heat the piezoelectric actuator during connection. But there are many disadvantages to gluing; the main one is curing time. Welding is another alternative, but when done in an oven, the temperature needed for this operation might destroy the heat sensitive actuator. The method described in this paper is laser soldering of piezoelectric actuator. The piezo actuator is mechanically and electrically connected to an alumina substrate by the use of tin solder heated by the mean of a laser diode. The advantage of the laser diode is its ability to selectively heat needed areas. Moreover, it is possible to control the energy brought to the system during the soldering process, thus reducing thermal impact on the piezoelectric actuator. Finally, the temperature can be monitored during the soldering process, allowing to control if the piezoelectric actuator was exposed to high temperature

Laser soldering of LTCC hermetic packages with minimal thermal impact

A novel laser soldering method for hermetic packaging of temperature sensitive devices such as organic electronics, micro- and nanostructures is presented in this work. The package combines a thermally optimized LTCC (Low Temperature Co-fired Ceramic) base with a glass lid. These two parts are soldered together by the use of a laser diode. The advantages of the laser soldered joint is its hermeticity to water and air in regard to glue and plastic, as well as the possibility to heat only the soldered joint. The power of the laser diode has to be controlled during the soldering process. We propose a solution based on temperature monitoring by the mean of a pyrometer. Heat transfer from the heated solder joint to the encapsulated device can be reduced by structuring the LTCC base, which also reduces the required optical power. Several schemes such as cavities under the joint and local thinning of the base are studied. Key words: Packaging, LTCC, laser soldering, thermal impac