SCD developed the first vacuum etching machine in China, with vacuum flood bar in the etching chamber; no pool effect; etching factor is up to 4.0.

Conclusions: Both etching of porcelain surface and use of silane yield higher bond strength, but the etching is the chief factor.

Then the profile of etching front is studied and the forming factors of the triangle at etching front are analyzed. The results show that the major factor of the triangle formation is stress.