Effects of the concentration of polycarbonate

C

pc

(domestic) and Lexan (

L

pc

) etching products in NaOH solution on bulk etch rate (

V

g

) and relative sensitivity (

V

T

/

V

g

)were studied at 60 and 70℃ and in the solution of 6 and 7 mol/1 NaOH. It is shown that the bulk etch rate (

V

g

) for

L

pc

and

C

pe

increases with increasing concentration of the etching products in NaOH solution. After the concentration of etching products reaches a certain value

the bulk etch rate reaches a maximum and remains unchanged. The relative sensitivity

V

T

/Vg

is found to be independent of etching product concentration.