Novel cold chemical lamination bonding technique—A simple LTCC thermistor-based flow sensor

The LTCC technique enables fabrication of microfluidic devices. The structures consist of channels, chambers and screen-printed passives. The lamination is a quality-determining process in the manufacture of the fluidic modules. The commonly used bonding method is thermocompression. The tapes are joined together at high pressure (up to 30 MPa) and temperature (up to 80 °C) for 2–15 min. Although these parameters allow good LTCC module encapsulation, the quality of the chamber geometry is strongly affected by high pressure and temperature. The cold chemical lamination (CCL) technique presented in this paper, a solvent-based method, largely avoids these problems. A film of a special solvent is deposited on the green tape, and softens the surface. The tape layers are then stacked and compressed at low pressure, below 100 kPa, at room temperature. The fabrication of a simple LTCC thermistor-based flow sensor is presented here to compare both lamination methods. The test device consists of one buried thermistor screen printed on a bridge hanging in a gas/liquid channel. The basic sensor parameters (measurement range, working temperature, output signal, working pressure and measurement error) are analyzed.