  For manufacturing Micromegas detectors, the "bulk" method based on
photoetching, was successfully developed and widely used in nuclear and
particle physics experiments. However, the complexity of the method requires a
considerable number of advanced instruments and processing, limiting the
accessibility of this method for production of Micromegas detectors. In view of
these limitations with the bulk method, a new method based on thermal bonding
technique (TBM) has been developed to manufacture Micromegas detectors in a
much simplified and efficient way without etching. This paper describes the TBM
in detail and presents performance of the Micromegas detectors built with the
TBM. The effectiveness of this method was investigated by testing Micromegas
detector prototypes built with the method. Both X-rays and electron beams were
used to characterize the prototypes in a gas mixture of argon and CO2 (7%). A
typical energy resolution of ~16% (full width at half maximum, FWHM) and an
absolute gain greater than 10^4 were obtained with 5.9 keV X-rays. Detection
efficiency greater than 98% and a spatial resolution of ~65 {\mu}m were
achieved using a 5 GeV electron beam at the DESY test-beam facility. The gas
gain of a Micromegas detector could reach up to 10^5 with a uniformity of
better than 10% when the size of the avalanche gap was optimized thanks to the
flexibility of the TBM in defining the gap. Additionally, the TBM facilitates
the exploration of new detector structures based on Micromegas owing to the
much-simplified operation with the method.
