Standard Plastic Package Research Articles

In-Situ Analysis of Deformation and Mechanical Stress of Packaged Silicon Dies With an Array of Hall Plates

A technique is presented that allows to simultaneously measure stress and deformation of packaged silicon dies. Required is a test chip with an array of Hall plates assembled in a package made of nonmagnetic materials. Exploiting the highly anisotropic magnetic sensitivity of the integrated Hall plates in an external magnetic field, makes it possible to measure the deformation. Moreover, the piezoresistive and piezo-Hall effect allow for measurements of several stress components without extra sensor elements. An optical measurement verifies the new technique, and a standard plastic package is exemplarily analyzed at different temperatures, under the influence of an external force, and at moisture load. The combined knowledge of stress and deformation allows for deeper insight into the mechanical impact of packaging on integrated circuits.

Sensor Packaging: New Challenges for New Applications

Advantages of silicon-based sensors are compatibility with CMOS, improved robustness and reliability, smaller size and reflow compatibility. Biosensors that use an electrical measurement principle need electrical connections and fluidic access to the die. This only works when the electrical interconnects are kept clean of biofluid and when the package is compatible with the biofluids, receptor chemicals and other sensor elements. In addition, the package needs to be very cheap. A simple plastic overmolded package with a hole in the compound at the sensor location is an effective solution. RFID sensors also need direct die access for gass and pH sensing. They require the integration of processor, memory, clock, battery and antenna. The package format depends on the application. For checking the quality of perishables during transport or in a store, a disposable flexible tag is needed whereas for smart building sensors, a plastic module is more appropriate. For the sensor tag, a flexible substrate and flip chip bare dies are used. Direct die access is realized by an opening in the flex. Battery and antenna are printed on the flex. Automotive sensors that are used under the hood need to cope with very high operating temperatures with peak temperatures of up to 200 °C and they need to be delamination free. The critical points in the standard plastic packages used today are the molding compound and the wire-bonds. Standard packages can be used up to 150 °C. For higher temperatures, the molding compound and the wire-bond interconnect are being improved.

A new methodology for the identification of ball bond degradation during high-temperature aging tests on devices in standard plastic packages

We describe a new methodology for the “in situ” identification of wire-bond degradation at early stages during high-temperature aging tests on devices with standard plastic packages. This methodology is based on the measurement of the changes in wire bond resistance, which is deduced from the I( V) characteristics of the ESD protection diodes on each contact pad of the circuit. In a first stage, the measurement procedure is described, with emphasis on the initial temperature calibration. This procedure allows for an “in situ” measurement sequence, where the packages stay in the aging chamber, at elevated temperature, during the electrical tests on the pad connections performed at different aging durations. By following accurately the package temperature, using a thermocouple, it is possible to correct for slight changes and thus get a reliable I– V measurement for each interconnection. In the second stage, the aging test results are described, showing the evolution of each individual interconnection. We were able to identify the onset of wire-bond degradation through the progressive increase of their resistance. To allow for better determination of the degradation process, once an increase in wire bond resistance was detected, complete I( V) curves were recorded at the pin(s) of interest. For each pin of a TQFP64 package, the tests were performed at least twice a day, with increased density when initial failure is detected (one complete measurement every 3 h). This strategy allowed for the detection of different behaviors on the wire bonds: good ball bonds (i.e. ball bonds with no change in their resistance), ball bond with intermittent opens (these ball bonds are in the process of degradation, and thermo-mechanical stresses induced in the resin by very small temperature changes are sufficient to open or close the circuits) and completely destroyed ball bonds, for which the resistance stays in an “high” level. This approach to wire-bond degradation in plastic packages is very powerful in terms of the number of interconnections which can be followed “in real time” and especially has the advantage, over other classical approaches, that the devices under test stay operational, contrary to what occurs with other types of destructive testing. These electrical test results are compared with metallographic investigations performed after a series of mechanical tests on the ball bonds (wire pull/ball shear tests) on a set of identical devices which undergone exactly the same High Temperature Storage (HTS) aging for 2000 h at 165 °C.

ISAAC: [formula omitted]ntegrated [formula omitted]ilicon [formula omitted]utomotive [formula omitted]celerometer

The pervasiveness of automotive passive restraint systems has emphasized the need for improving system reliability while simultaneously reducing the cost and size of the system. This paper describes the integrated silicon automative accelerometer (ISAAC), which consists of a silicon micromachined die fabricated in a dissolved-wafer process and a CMOS ASIC trial are combined in a standard plastic package. The resultant device meets the functional, cost, and reliability requirements of the next generation of automotive passive restraint systems.