Thermal flow meter with diaphragm forming a reduced pressure sealed space

A thermal flow meter comprising:

• a bypass passage through which a measurement target gas received from a main passage flows;
• and
• an air flow sensing element which measures a flow rate of the measurement target gas by performing heat transfer with the measurement target gas flowing through the bypass passage,
• wherein the thermal flow meter includes at least a circuit package which contains the air flow sensing element,
• wherein a gap is formed in a rear surface of the air flow sensing element to form a diaphragm in an air flow sensing area of the air flow sensing element,
• wherein the gap is a sealed space reduced in pressure compared to an atmospheric pressure,
• wherein the air flow sensing element and a sealing plate are bonded to make the gap the sealed space,
• wherein the circuit package is molded with a polymeric resin in a state where the air flow sensing element and the sealing plate are bonded,
• wherein the polymeric resin is molded to cover at least an outer side edge of a bonding portion between the air flow sensing element and the sealing plate,
• wherein the air flow sensing element is mounted on a plate, and
• wherein the plate has a backside that is covered with the polymeric resin to expose an area on the backside of the plate corresponding to an area on which the air flow sensing element is mounted.