A thermode having a relatively long and thick blade composed of a high thermal conductivity, low thermal expansion material, e.g., molybdenum, provides an elongated contact surface for bonding a row of leads of an electronic component to a circuit board. A thermode holder is coupled to the blade by means of a plurality of struts, including a pair of outer struts, each connected at one end of the respective ends of the blade and at an acute angle facing the other outer strut, and a pair of shorter inner struts, each connected with the blade intermediate the ends of the blade and at an acute angle facing the outer strut adjacent thereof, such that in response to a force urging the blade against the circuit board, the outer struts cause a negative deflection of the blade with respect to the board and the inner struts decrease the magnitude of the deflection. The blade is heated by electric current supplied thereto from a transformer through the inner and outer struts. A step in the contact surface of the blade provides an acceptally narrow bonding footprint while allowing use of a desirably thermally massive thick blade.