Video bond lead locator

A method of determining the position of leads on a semiconductor lead frame comprising the steps of:

• illuminating said lead frame with light from a light source;
• sensing light intensity levels reflected from said lead frame;
• generating a digital data set representing pixel intensity levels of said reflected light from a plurality of leads;
• defining a first corridor in said data set, said first corridor having a length and width covering a plurality of leads;
• generating a first signature of said data set within said corridor along the length thereof, said signature being the widthwise summation of said pixel digital data at pixel columns along the length of said corridor;
• determining the first order derivatives of said first signature and storing said first order derivatives in one array;
• scanning said one array to determine the regions along the length of said corridor having the general characteristics of leads;
• storing the positions of said regions in another array;
• and
• scanning said another array to determine which of said regions have a dimension exceeding the minimum dimension of leads.

A method of determining the position of leads on a semiconductor lead frame with respect to a wire bonding apparatus comprising the steps of:

• illuminating said lead frame with light from a light source;
• sensing light intensity levels reflected from said lead frame;
• generating digital data representing pixel intensity levels of said reflected light from a plurality of leads;
• storing said pixel digital data in a memory;
• defining a first corridor in said memory, said corridor having a length and a width covering a plurality of leads;
• generating a first signature of said data within said corridor along the length thereof, said first signature being the widthwise summation of said pixel digital data at pixel columns along the length of said corridor;
• determining the location of candidate lead boundaries from said first signature by analyzing the changes in said first signature along the length of said corridor and storing said locations in a first array;
• scanning said first array to determine regions between said candidate lead boundaries typical of leads, the positions of said regions being stored in a second array;
• and
• scanning said second array to determine which of said regions have a dimension exceeding the minimum dimension of leads.

An image processing system for determining the position of leads on a semiconductor lead frame for use with a wire bonding apparatus comprising:

• a light source for illuminating said lead frame;
• means for sensing light intensity levels reflected from said lead frame;
• means, responsive to said sensing means, for generating digital data representing pixel intensity levels of said reflected light from a plurality of leads;
• memory means, responsive to said generating means, for storing said pixel digital data, said memory means including a first and a second memory array;
• control means for defining a first corridor in said memory means, said corridor having a length and a width covering a plurality of leads, for generating a signature from said digital data within said corridor along the length thereof, said signature being the widthwise summation of said pixel digital data at pixel columns along the length of said corridor, for determining the locations of candidate lead boundaries from said signature by analyzing the changes in said signature along the length of said corridor, and for storing said locations in said first array, said control means further including means for scanning said first array to determine regions between said candidate lead boundaries typical of leads and for storing the position of said regions in a said second array, said second array being scanned by said control means to determine the position of said leads by determining which of said regions have a dimension exceeding the allowed dimension of leads.

A method of determining the actual position of a lead on a lead frame prior to bonding a fine wire thereon employing an automatic fine wire bonder of the type equipped with an improved pattern recognition system, comprising the steps of:

• illuminating a plurality of leads of a lead frame including the lead from a lead to be bonded and leads adjacent thereto;
• sensing the analog pixel intensity levels from said plurality of lead frame leads;
• converting said analog pixel intensity levels to digital data;
• storing said digital data representative of said pixels in a memory map;
• combining columns of digital pixel data to provide a one dimensional digital signature;
• determining the location of candidate lead boundaries by detecting large differential changes in adjacent columns of digital pixel data of said signature;
• storing the location of candidate lead boundaries in a first memory array;
• and
• comparing the distance between candidate lead boundaries with data representative of ideal predetermined distances between lead boundaries, and selecting the two unique lead boundaries from lead boundaries representative of a plurality of leads that fall within predetermined portion of said signature as the lead boundaries and the location of the lead boundaries of the actual lead to be bonded.