The invention relates to a blade and a technique, in particular to the formula of a diamond ultrathin blade for cutting QFN baseplates and a manufacturing technique thereof. The invention is characterized in that the blade is made by mixing copper adhesive and auxiliary metallic stuffing the proportioning sum of which is 100%, wherein the copper adhesive accounts for 68%, and has a mean grain size of 0.46 mu m; the auxiliary metallic stuffing contains 3% of lead powder, 10% of tin powder, 10.5% of silver powder, 8% of ferrous powder and 0.5% of graphite powder; and diamond abrasive with the density of 0.66G/CBM is added in and mixed with the auxiliary metallic stuffing and the adhesive according to the size of the blade. The manufacturing technique of the compound diamond blade has the following steps: 1) mixing; 2) filling mould and charging; 3) prepressing and hot pressing in a fixed mould; 4) unloading mound and hardening; 5) protecting atmosphere and cooling; 6) mechanically processing; 7) inspecting products; and 8) branding, packing and warehousing. The blade has little compatibility to steel materials, favorable cutting wettability, small friction with processed materials and long service life.