Abstract: A connective medium is provided for use in ball grid assemblies for detachable connections between electronic devices and circuit boards. The medium includes novel, discrete spheres defining an inner metallic, spherical core and one or more outer, electrically conductive concentric, hard and non-deformable metallic layers of nickel, copper or alloys thereof and a coating of silver or gold thereon.

Abstract: A solar energy collector is disclosed. The collector has a frame, a window and an absorber enclosed by the frame and a combined heat trapping and heat shielding arrangement between the window and the absorber. The trapping and shielding arrangement consists of a series of vanes extending from side to side of the frame and, in a heat trapping position, from the window to the absorber. In a heat shielding position, the vanes overlap when projected upon the plane of the absorber so that incident radiation must pass through plural vanes before reaching the absorber.