An embodiment includes a system comprising: a polymer substrate including a plurality of voids; and a plurality of metal pins; wherein a first pin, included within the plurality of metal pins, includes: (a)(i) first and second arms that couple to each other by way of an arcuate member, (a)(ii) a middle portion including a middle diameter, a proximal portion including a proximal diameter, and a distal portion including a distal diameter; wherein (b)(i) the middle portion is between the proximal and distal portions, (b)(ii) the middle diameter is less than the proximal and distal diameters, and (b)(iii) the proximal portion, but not the distal portion, is included within one of the plurality of voids. Other embodiments are described herein.