Heat exchanger tube precursor and method of producing the same

A method of producing a heat exchanger tube precursor, the method comprising the steps of:

• classifying a pre-classification Si powder to obtain a post-classification Si powder in which 99% particle diameter (D99) is 5 μm or more and 20 μm or less, an amount of coarse particles having diameters of not smaller than 5 times (D99) is less than 1 ppm by volume, and 50% particle diameter (D50) of the Si powder is (D99)×0.05 or more and (D99)×0.7 or less;
• preparing a coating material including the post-classification Si powder, a Zn-containing flux, a Zn-free flux, and a binder;
• and
• applying the coating material on an Al alloy tube, wherein an amount of the Si powder applied on the Al alloy tube is in a range of 1 g/m2 to 5 g/m2, an amount of the Zn-containing flux applied on the Al alloy tube is in a range of 3 g/m2 to 20 g/m2, (D99) denotes a critical diameter defined such that cumulative volume of particles not larger than (D99) constitute 99% by volume of all the particles, and (D50) denotes a critical diameter defined such that cumulative volume of particles not larger than (D50) constitute 50% by volume of all the particles.