Abstract: A method of making an aperture of a predetermined shape into a dielectric substrate which will lockingly receive a deformable contact pin. It includes providing a dielectric material which shrinks in response to a heat treatment by an amount which is different in one direction from that in another direction, and which irreversibly changes dimensions in its two orthogonal directions in proportion to this difference. An aperture is formed in such a material, in a direction normal to the plane of the two orthogonal directions and the material is subjected to a heat treatment that causes a differential shrinkage in the aperture and a change in the shape of the aperture. A deformable contact pin is then forced into a locking position in the aperture.