Method for determining coplanarity of electrical contact of BGA type packages prior to electrical characterization

A method of performing electrical characterization of a chip scale package, comprising the steps of:

• applying impressionable material on a contact surface of an isolation plate of a test fixture;
• placing the isolation plate on the tops of an array of electrical contacts of a chip scale package such that the impressionable material contacts at least some of the tops of the electrical contacts;
• pressing the isolation plate against the array of electrical contacts such that at least some of the electrical contacts make an impression in the impressionable material;
• examining the impressions in the impressionable material to determine the co-planarity of the tops of the electrical contacts in the array;
• and
• further comprising correcting non-planarity of the tops of the electrical contacts as a function of the impressions in the impressionable material.

A method of preparing a chip scale package having a plurality of electrical contacts for electrical characterization, the method comprising the steps of:

• determining non-planarity of tops of the electrical contacts in an array of the chip scale package;
• and
• planarizing the tops of the electrical contacts as a function of the determination of non-planarity of the tops of the electrical contacts;
• wherein the step of determining includes:
• applying an impressionable material to a planar surface of a flat plate;
• pressing the planar surface and the impressionable material against the tops of the array sufficiently to create impressions of the electrical contacts in the impressionable material;
• and
• examining the impressions in the impressionable material to determine non-planarity of the tops of the array.