Overcoming Some of the Challenges in 3D Micro-Assembly Techniques to Package MEMS Devices

Special Article on Packing and Reliability of Nano and Micro-electro-mechanical-system (N/MEMS) Devices

Austin J Nanomed Nanotechnol. 2014;2(6): 1032.

Overcoming Some of the Challenges in 3D Micro-Assembly Techniques to Package MEMS Devices

Rezaeisaray M, Lueke J, El Gowini M, Yue S, Raboud D and Moussa W*

Department of Mechanical Engineering, University of Alberta, Canada

*Corresponding author: Moussa W, Department of Mechanical Engineering, University of Alberta, Canada

Received: July 25, 2014; Accepted: August 20, 2014; Published: August 22, 2014


This article compiles the most important packaging techniques for micro electromechanical systems (MEMS). In addition, the main electrical interconnection techniques are investigated: wire-bonding, tape automated bonding (TAB), adhesive-based bonding, and flip-chipping. For each specific technique, some examples are demonstrated which were developed or adapted in our lab. A low cost micro-dispensing technique has been developed to run precise dispensing using manual dispensers. An improvised approach of using flexible printed circuit boards (PCBs) as well as conventional solid PCBs is depicted to electrically bond MEMS prototypes and prepare for tests. This article demonstrates adapting 3D printing for packaging of overhanging MEMS structures. This packaging technique is known for its low cost and quick manufacturing capacity and it is also capable of building structures with bio-compatible materials. Additionally, a small vacuum chamber has been designed and manufactured to examine the mechanical response of MEMS devices under vacuum before fully package them. Although this paper provides a platform to deal with some of the main 3D packaging challenges, the same techniques could be expanded for numerous applications and for mass production of MEMS devices.

Keywords: Packaging; Micro-assembly; Wire-bonding; TAB; Flip-chipping; Adhesives


The packaging is a vital bridge between semiconductors and printed circuit boards (PCBs) [1]. Packaging in general terms is categorized in various subsections such as biological micro-electromechanical systems (bio MEMS) packaging [2,3], packaging of optoelectronics [4] and radio frequency (RF) devices package [5]. However, the package must satisfy multiple functions including: protection (from the surrounding environment); connectivity (electrical, material transport, radiant energy, external force); compatibility (chip-to-package, package to PCB); routing (electrical, materials); mechanical stress control; thermal management; assembly simplification; testability; and rework ability [1]. Although the packaging, testing and calibration importance and cost (70% of the manufacturing cost [6]) are more than even fabrication, it has gained less consideration in literature. It is known that the packaging belongs to industrial and commercial fields [7]. However in this article, the focus is on low cost techniques to provide some ideas for MEMS and microelectronics researchers to consider when dealing with their packaging and testing experiences. The article starts with a brief overview of packaging possibilities. Die separation which is the first step of most packaging processes comes next. Then, three possible ways of providing electrical connections are presented followed by two other sections discussing the package for wafer level tests and package for the individual dies.

Available Packaging Techniques for MEMS1

Packaging of micro-sensors and micro-actuators is different than general microelectronic devices [7]. In the case of microelectronics, a particular package type can be used for various chips. The size and number of wire-bonds might change but the shape could be the same. However for MEMS devices, the package design crucially depends on the function of the device [7]. Therefore, the MEMS device and its package must be considered simultaneously to take into account each design's limitations for designing the other.

Individual MEMS devices must be diced and then mounted on a package and attached to a metallic, ceramic or plastic platform. A number of dicing and die-attach [8] techniques have been reported. Wiring and electrical interconnections are usually the next process in packaging. Various packaging techniques have been developed based on the specific device's requirements. Micro fluidic interconnections are needed for micro fluidic devices such as micro pumps and micro valves. Ceramic packaging, which is one of the main techniques of electrical packaging, has been extended to the MEMS packaging. Many commercial micro machined sensors use ceramic packaging. This packaging is expensive comparing to other techniques [9]. However, the high reliability, interesting material properties such as electrical insulation and hermetic sealing and easy shaping keeps ceramic packaging one of the main techniques in electronic packaging. Metal packaging, molded plastic packaging, and multichip modules are some other MEMS packaging methods [10]. Integrated MEMS devices merge microstructures and microelectronics on a single substrate to reduce overall size, electrical noise, and system power requirements. However, there are some challenges in terms of materials, process incompatibilities, and high cost [11-13]. As an alternative, hybrid packaging with separate MEMS device and electronic processes could be exploited [14].

Figure 1 demonstrates the path should be taken in MEMS manufacturing. Table 1 provides a summary of the most important available packaging techniques. Most of the information in Table 1 is taken from [15]. The focus of this article is to investigate electrical interconnections used for MEMS packaging and to review various mechanical packaging techniques developed for individual MEMS devices.