Fabrication method of lab-on-PCB devices using a microheater with a thermo-mechanical barrier

• Published in: Microelectronic engineering Vol. 194; pp. 31 - 39
• Main Authors: Franco, Emilio, Salvador, Blas, Perdigones, Francisco, Cabello, Miguel, Quero, José Manuel
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 05.07.2018; Elsevier BV
• Subjects: Barriers; Bonding; Circuit boards; Computer simulation; Lab-on-PCB; Microfluidics; Numerical prediction; Polymethyl methacrylate; Power supplies; Power supply; Printed circuits; Simulation; Substrates; Temperature; Thermal bonding; Thermo-mechanical barrier; Thermoplastic resins; Thermoplastics; Thermo-mechanical barrier; Thermoplastics; Lab-on-PCB; Thermal bonding; Microfluidics
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2018.02.019

A thermal method for bonding thermoplastics with a printed circuit board has been developed for its use in Lab on Chip applications. In order to define and control the bonded zones of the device, a thermo-mechanical barrier is included. The thermoplastic used is polymethylmethacrylate (PMMA), and the substrate is a double-side PCB. The copper layer is used to fabricate simultaneously a microheater and the thermo-mechanical barrier by wet etching, and the piece of PMMA used is micromilled before its bonding to the PCB. Once the PCB and the piece of PMMA are processed, a good alignment of both parts is important. After that, a controlled current is applied by a power supply in order to increase the temperature of the microheater. Time needed for bonding is predicted by numerical simulations of the whole system. As an example of a possible application of this procedure, the proposed method is applied to fabricate a two-dimensional hydrodynamic focusing device. This device has been tested showing an appropriate behaviour. The dimensions of the generated streams lie between 81 and 224 μm showing a good correspondence with the theory. In addition, the device presents a correct functioning, without leakages demonstrating that the bonding is good. The presented method has been studied in order to characterize the maximum pressure the whole device is able to withstand. In this case, the materials used withstand 481 kPa. This method can be easily extended to industrial production of microfluidic devices, such as lab on chips and μTAS. [Display omitted] •A mass production thermal method for bonding thermoplastics and PCB is proposed.•A microheater and a thermo-mechanical barrier are designed for performing the bonding.•The application of this method is microfluidic circuits fabrication.•The process has been tested in a hydrodynamic focusing circuit with good results.