Process for making circuit board or lead frame

A process for making a circuit board, comprising

• forming a first metal layer on an insulating substrate and forming a second metal layer on the first metal layer, the second metal layer having a smaller thickness than that of the first metal layer;
• applying a first resist on the second metal layer and patterning the first resist to form openings therein;
• etching selectively only the second metal layer through the openings of the patterned first resist;
• half-etching the first metal layer through a first mask comprising the first resist and the second metal layer located just under the first resist;
• applying a positive liquid second resist on the half-etched first metal layer from an upper surface of the first mask;
• exposing the positive liquid resist with light from the upper surface of the first mask and developing the positive liquid resist such that a protected portion of the positive liquid resist located under the first mask is unexposed and undeveloped;
• etching again the first metal layer through a second mask comprising the first mask and the protected positive liquid resist, to form a conductive pattern on the insulating substrate;
• and
• removing the first resist and the second resist.

A process for making a circuit board, comprising

• forming a first metal layer on an insulating substrate and forming a second metal layer on the first metal layer, the second metal layer having smaller thickness than that of the first metal layer;
• applying a first resist on the second metal layer and patterning the first resist to form openings therein;
• etching selectively only the second metal layer through the openings of the patterned first resist;
• half-etching the first metal layer through by a first mask comprising the first resist and the second metal layer located just under the first resist;
• applying a permanent-type positive liquid second resist on the half-etched first metal layer from an upper side of the first mask;
• exposing the positive liquid resist with light from the upper side of the first mask and developing the positive liquid resist such that a protected portion of the positive liquid resist located under the first mask is unexposed and undeveloped;
• etching again the first metal layer through a second mask comprising the first mask and the protected positive liquid resist to form a conductive pattern on the insulating substrate;
• and
• removing the first resist and the permanent-type positive liquid second resist, except for a part of the second resist protected to be unexposed and undeveloped.

A process for making a lead frame, comprising

• forming thin, second metal layers on respective surfaces of a metal plate;
• applying respective first resist layers on the second metal layers and patterning the first resist layers to form openings therein;
• selectively etching the second metal layers through the openings of the respective, patterned first resist layers to form first masks on corresponding opposite surfaces of the metal plate;
• half-etching the opposite surfaces of the metal plate through openings of the corresponding first masks
• applying a positive liquid second resist on the half-etched opposite surfaces of the first metal layer through the openings of the corresponding first masks;
• exposing the positive liquid resist with light through the openings of the first masks on corresponding opposite surfaces of the metal plate and developing the exposed positive liquid resist such that protected portions of the positive liquid resist located under portions of the corresponding first masks having no openings therein are unexposed and undeveloped, the protected portions of the positive liquid resist and the corresponding first masks together comprising respective second masks;
• etching the metal plate again at the opposite surfaces thereof through the respective second masks, to form a conductive pattern of the metal plate;
• and
• removing any remaining portions of the first and second resist layers.

A process for making a circuit board comprising:

• coating a metal layer formed on an insulating substrate with a first resist and patterning the first resist;
• forming light-blocking film on the patterned first resist;
• half-etching the metal layer through a first mask comprising the first resist and the light-blocking film;
• applying a positive liquid resist on the half-etched metal layer from an upper surface of the first mask;
• exposing the positive liquid resist with light from the upper surface of the first mask and developing the positive liquid resist such that a protected portion of the positive liquid resist located under the first mask masking is unexposed and undeveloped;
• etching again the metal layer through a second mask comprising the first mask and the protected positive liquid resist, to form a conductive pattern on the insulating substrate;
• and
• removing the first mask and the second masking from the conductive pattern on the insulating substrate formed on the insulating substrate.

A process for making a lead frame comprising:

• coating opposite surfaces of a metal plate with corresponding first resist layers and patterning the corresponding first resist layers forming openings therein;
• forming respective light-block films on the remaining portions of the corresponding patterned first resist layers to form first masks on corresponding opposite surfaces of the metal plate;
• half-etching opposite surfaces of the metal plate through openings of the corresponding first masks,
• applying a positive liquid resist on the half-etched opposite surfaces of the metal plate through openings of the corresponding first masks;
• exposing the positive liquid resist with light through the openings of the first masks on corresponding opposite surfaces of the metal plate and developing the exposed positive liquid resist such that a protected portion of the positive liquid resists, located under portions of the corresponding first masks having no openings therein, is unexposed and undeveloped, the protected portion of the positive liquid resist and the corresponding first masks together comprising respective second masks;
• etching again the metal plate at the opposite surfaces thereof through the respective second masks to form a conductive pattern of the metal plate;
• and
• removing any remaining portions of the first and the second masks from the metal plate.

A process for forming a fine pattern on a metal plate comprising:

• coating one or each of opposite surfaces of a metal plate with a respective first resist layer and patterning each respective first resist layer;
• forming a light-block film on each corresponding, patterned first resist layer to form a first mask on the one or each of the opposite surfaces of the metal plate;
• half-etching the metal plate on the one or each of the opposite surfaces thereof through openings of the corresponding first mask on the one or each of the opposite surfaces of the metal plate
• applying a positive liquid resist on the half-etched metal plate through openings of the corresponding first mask on the one or each of the opposite surfaces of the metal plate;
• exposing the positive liquid resist with light through the openings of the first mask on the one or each of the opposite surfaces of the metal plate and developing the exposed positive liquid resist such that a protected portions of the positive liquid resist located under respective portions of each corresponding first mask is unexposed and undeveloped, the protected portions of the positive liquid resist and the first mask, on the one or each of the opposite surfaces of the metal plate, together comprising a second mask on the one or each of the opposite surfaces of the metal plate;
• etching again the metal plate on the one or the opposite surfaces thereof through the respective second mask on the one or each of the opposite surfaces of the metal plate;
• and
• removing any remaining portions of the first and the second masks from the metal plate.