NOVELTY - An overmolding insert (10) comprises a base having opening(s) in a first surface, and hollow projection(s) (20) having a first opening in communication with the first surface opening and a second opening at the projection terminal portion. The insert side walls (50), end walls (70, 80), and first surface define a partially closed space, with the terminal portion of the projection extending beyond the partially closed space.    USE - Used to make heat exchanger (claimed), such as solar collectors.    ADVANTAGE - The insert permits efficient, low cost manufacturing of heat exchanger. The heat exchanger is provided having improved interfacial bond between its manifold and its hollow conduits without resorting to higher than normal injection molding temperatures or preheating the inserted conduits. This heat exchanger is better able to withstand the thermal and mechanical stress exerted upon it during operation than known heat exchangers.    DETAILED DESCRIPTION - An overmolding insert comprises a base having opening(s) in a first surface, with the opening being in communication with a second surface opposite the first surface; and hollow projection(s) extending from the first surface of the base, and having a first opening in communication with the opening of the first surface and a second opening located at a terminal portion of the hollow projection. The insert further comprises two opposed side walls, each side wall being joined to the first surface; and two opposed end walls being joined to an opposite end of the first surface and extending from one side wall to the other side wall, such that the side walls, the end walls, and the first surface define a partially closed space, where the terminal portion of the hollow projection extends beyond the partially closed space. INDEPENDENT CLAIMS are also included for:    (a) a heat exchanger comprising hollow conduits; first manifold having an internal space, and being connected to first end of each conduit such that the hollow conduit is in communication with the internal space; second manifold connected to second end of each conduit; where at least one of the first and second manifolds is joined around the conduit ends and over-molding insert(s) such that a hollow conduit is fitted over a hollow projection; and    (b) a process for manufacturing a heat exchanger manifold, comprising removably inserting a removable projection into opening in a first surface of the overmolding insert such that the projection extends from the first surface and beyond the partially closed space; fitting an end of a hollow conduit over the removable projection; molding molten polymeric material over the over-molding insert and the hollow conduit end to form a manifold; and removing the removable projection from the manifold.    DESCRIPTION OF DRAWING(S) - The figure is a top elevation view of overmolding insert intended to provide constricted inlet at each and every hollow conduit junction with the manifold.    Overmolding insert (10)    Projections (20)    Side walls (50)    End walls (70, 80)    Terminal segment (90)