Top-Side Surface Mountable Auto-placeable Coin

Current heatspreaders used for mounting RF devices have several manufacturing disadvantages.  Motorola has patented the "coin" concept, which is a small copper slug directly attached to the underside of a PCB.

Discussed here is an improved coin design that is mounted from the topside of the board eliminating many of the manufacturing issues associated with coined boards.

The coin design and mounting in Figures 1 and 2 show how the coin could be designed as top-side surface mountable solution, as well as auto-placeable by adding a raised ledge to the coin.  This coin is assembled from the top surface.  Attachment is achieved using traditional solder pastes under the ledge, which bonds the coin in place as well as produces a ground path through vias. 

The main advantage of this idea is that it requires only one manufacturing process to place this part.  This is in contrast to bottom-mounted coins, which would have to go through two process steps. With this coin design approach, one process step can be achieved without the use of high temperature solder.

An additional advantage is the elimination of the stack-up tolerances.  The PCB thickness typically is the gating item in tolerance stackup (tolerance up to 10%). The top mounted coin solution registers off the bottom of the coin ledge to the top of the mounting, and is much more controllable.  It also can accommodate an...