Chingfu Tsou

Silicon-based Packaging Platform for Light Emitting Diode

A novel concept of silicon-based packaging platform with microreflector and embedded electrode-guided interconnections was development for a package component of a light-emitting diode (LED). TracePro and ANSYS software were respectively used to understand the optical and thermal characteristics of the package component. Simulation results show the microreflector at several certain specific dimensions can be used to achieve high brightness, and the carrier made of silicon wafer compared with that of aluminum stage can minimize the thermal stresses caused by mismatch of thermal expansion coefficient. The novel packaging platform was fabricated by silicon bulk micromachining and solder reflow techniques. Various solutions in fabricating embedded solder interconnections were explored to accomplish the electrode-guided interconnections. Experimental results show the method using solder paste reflow can achieve better yield and performance. The electrical resistances of such solder interconnections with the height of 100 mum were measured to be less than 5 Omega. As such, this technique can be applied broadly in packaging for conventional optoelectronic semiconductor devices such as laser diodes and image sensors

A novel self-aligned vertical electrostatic combdrives actuator for scanning micromirrors

A novel self-aligned vertical electrostatic combdrives actuator has been developed and demonstrated, which enhances the capabilities and applications of high aspect ratio silicon-on-insulator microelectromechanical systems (SOI-MEMS) by enabling additional independent degrees of freedom of operation: both upward and downward vertical pistoning motion as well as bi-directional rotation. The present method utilizes four aligned masks greatly simplifying the existing SOI-MEMS fabrication methods for manufacturing high performance scanning micromirrors. Results from the micromirror device for the novel vertical combdrives show that a mechanical tilt angle of ±1° at 100 Vdc was achieved for a 450 µm diameter micromirror. The scanning micromirror can scan a large angle 62° at the resonance frequency of 10.46 kHz with a sinusoidal voltage input of 60 V in amplitude.

On the out-of-plane deformation of V-shaped micromachined beams

V-shaped beams are widely applied for the suspension of the sensors, fiber holders, and the suspension arms of atomic force microscopes. The performance of the V-shaped beam is highly dependent upon its initial out-of-plane deflection. This paper reports on the exploration of the out-of-plane deformation of V-shaped micromachined beams. A finite element model has been established to predict the deformation of a V-shaped micromachined beam. The fabrication and characterization of various shapes of SiO2 V-shaped micromachined beams has been performed to observe the out-of-plane deformation caused by residual stress. With the difference between the analytical and experimental results, an etching process dependent mechanism has been discussed. Thus the design criteria to fabricate a flat V-shaped beam is accomplished.

A New Method for Microlens Fabrication by a Heating Encapsulated Air Process

This letter reports a new method to fabricate thin microlens array on a silicon substrate by a heating encapsulated air process. We use silicon bulk micromachining, wafer-to-wafer bonding, and photoresist (PR) spin coating to achieve the air sealing process. Under a heating process, the PR filled in the micro-through-hole of cap wafer is compressed by the thermal expansion of the sealed air to form a thin microlens with out-of-plane sphere shape. By adjusting the heating temperature and the sealed air volume, the curvature and size of the lens are controllable. A typical microlens with a diameter of 1475 mum and sag height of 486 mum was fabricated. The calculated radius of curvature and focal length are about 800 and 1200 mum, respectively. The fabrication provides an alternative way to manufacture thin microlens or microlens mold serve as master elements for replication

Design and fabrication of acoustic wave actuated microgenerator for portable electronic devices

An acoustic wave actuated microgenerator for power system applications in mobile phone was design, fabricated, and characterized. We used the acoustic wave of human voices or speakerphone by way of an electromagnetic transducer to produce electrical power for charging or to run a portable electronic device. The proposed microgenerator is composed of a planar coil, a suspension plate with supporting beams and a permanent magnet. In this paper, the dynamic response of the suspension structure and the variation of the induced magnetic flux were characterized by using commercial finite element analysis and Ansoft Maxwell EM3D software, respectively. The electroplating nickel and silicon bulk micromachining techniques were used to fabricate the suspension plate and planar coil, and by integrating a permanent magnet as well as wafer to wafer adhesion bonding to accomplish the microgenerator assembly. The experimental results shown the typical microgenerator with a planar dimension of 3 mm times 3 mm, the maximum induce-voltage 0.24 mV was generated at the driving frequency of 470 Hz. The dynamic response of microgenerator can be designed to meet a specific acoustic driving frequency to increase the efficiency of energy harvesting.

Novel Silicon-Based LED Packaging Module With an Integrated Photosensing Element

This letter presents a novel design for a silicon-based light emitting diodes (LEDs) packaging module with an integrated photosensor. The carrier substrate for the LED submount and a photosensitive element are directly fabricated on a silicon wafer, using ion doping and inductively coupled plasma etching, thereby achieving a smart LED packaging module featuring miniaturization, integration and low cost. The subsequent assembly, with a specific heat sink and a shelled optical cap, results in a decrease in thermal effects and improves measurement sensitivity. The typical experiment result shows that the operating temperatures of the LED die and the photosensing element remain below 70°C and 45°C, respectively, when the input current to the LED is 0.3 A. The sensitivity of the photosensing module is 8.2 μA/nt for a chip size of 1×1 × 0.15 cm3. The working temperature and photosensitivity of this packaging module can be improved by using a system with high heat dissipation efficiency.

A Novel Silicon-Based LED Packaging Module With an Integrated Temperature Sensor

The thermal management of light-emitting diode (LED) packaging modules has become more important in the past decade, especially for high-powered LED chips, which produce high temperatures during lighting, resulting in luminance decay and color temperature drift. For this issue, this paper proposes a novel silicon-based LED packaging module with an integrated temperature sensor. The LED die is mounted directly on a silicon substrate with a resistive nickel/titanium bilayer temperature sensor, which monitors the temperature variations in the LED inside the package, in real time. The thermal conductivity characteristics and the sensor performance for the specified packaging modules are evaluated using finite element analysis and by experiment. The experimental results shows that when the thickness of the bilayer sensing film and its equivalent length, within a sensing area of 1.4 × 1.4 mm2 , are 0.2 μm and 72.3 mm, respectively, a high sensitivity measurement of 30.4 Ω/°C is obtained and good linear output is achieved, at a working temperature for the LED of less than 120°C. A miniaturized, integrated, low-cost smart LED packaging module is implemented using this co-packaging method.

A Novel Wafer-Level Hermetic Packaging for MEMS Devices

Some emerging microelectromechanical systems (MEMS) devices such as high-performance inertial sensors and high-speed actuators must be operated in a high vacuum and in order to create this vacuum environment, specific packaging is required. To satisfy this demand, this paper presents a novel method for hermetic and near-vacuum packaging of MEMS devices. We use wafer-level bonding technology to combine with vacuum packaging, simultaneously. For this packaging solution, the wafers with air-guided micro-through-holes were placed on a custom-built design housed in a vacuum chamber maintained at a low-pressure environment of sub-10 mtorr. Packaging structure is then sealed by solder ball reflow process with the lower heating temperature of 300degC to fill up micro-through-hole. Experimental results shown the hermetical packaging technique using solder sealing is adapted to the wafer-level microfabrication process for MEMS devices and can achieve better yield and performance. Thus, this technique is very useful for many applications with high performance and low packaging cost can be obtained due to wafer-level processing.

Measuring thin film elastic modulus using a micromachined cantilever bending test by nanoindenter

It is convenient to characterize thin film material properties using commercially available nanoindentation systems. This study aims to discuss several considerations while determining the thin film elastic modulus by means of a microcantilever bending test using a commercial nanoindentation system. The measurement results are significantly improved after: 1. the indentation of the film during the test is considered and corrected, and 2. the boundary effects are considered in the model by finite element method. In application, the elastic modulus of electroplating nickel film 11 μm thick was characterized.

Electroplated nickel micromachined probes with out-of-plane predeformation for IC chip testing

This paper presents a new type of electroplated nickel micromachined probe with out-of-plane predeformation for next generation integrated circuit (IC) chip testing probe card applications. The probe card was fabricated using silicon bulk micromachining, titanium (Ti) deposition, nickel (Ni) electroplating and laser scribing processes. We use the effect of the residual stresses of thin-film deposition on flexible micromachined probes to produce a large out-of-plane predeformation and combine the post-electroplating technique to further increase the probes thickness and therefore enhance its stiffness. The typical micromachined probe had a thickness of 10–25 µm, a width of 20 µm and a length of 150 µm. The maximum out-of-plane deflection of the fabricated nickel probe was approximately 55 µm. The probes pitch can be designed to be less than 50 µm to meet the demands of fine pad pitch probing. This probe card is potentially capable of providing a very large number of micromachined probes in an array format, and this is designed also to satisfy the requirements for high resolution and low cost wafer-level testing.