Method for making a probe preserving a uniform stress distribution under deflection

A method for making a probe which preserves a uniform stress distribution when experiencing a deflection due to an overdrive applied to said probe, said method comprising the following steps:

• a) providing a blank of electrically conductive material;
• b) defining in said blank a probe having a top edge, a bottom edge, a tip and a distal end opposite said tip;
• c) forming a beam portion of length L in said blank between an end point of said top edge and an inflection point along said top edge, said beam portion having a varying width w(x) between said top edge and said bottom edge, where x=0 at said end point and x=L at said inflection point, said width w(x) being equal to a reference width W at said inflection point, said beam portion having a straight bottom edge;
• d) forming said tip portion to have a tip length T, an outer edge, an inner edge and a point of contact at the location where said outer edge and said inner edge join, said inner edge opposite said outer edge being approximately straight, said tip having a variable breadth m(x) between said outer edge and said inner edge, where x=0 at said point of contact and x=T at said end point, said breadth m(x) being equal to a reference breadth M at said end point;
• e) shaping the curvature of said outer edge to fit a parabola by setting said breadth m(x) in accordance with the following equation:
• ##EQU7## wherein b is the thickness of said probe, .sigma. is the stress, and x ranges from 0 to T and F.sub.1 is the component of a test force F normal to said tip, such that when said overdrive is applied and causes said tip to contact a pad of a circuit under test with said test force F, F.sub.1 distributes itself uniformly in said tip, thereby forming said probe preserving the uniform stress distribution inside said tip.