Abstract: An apparatus and method for selectively etching an encapsulant forming a package of resinous material around an electronic device includes a etchant solution source and an etching assembly including an etch plate and a movable cover forming an etching chamber. An etch head is supported by the plate and the device package is mountable in the chamber on the etch head. A first syringe pump pumps a first quantity of etchant into the etch head and a second syringe pump agitates or oscillates at least part of the first quantity of etchant repeatedly into and out of an etched cavity formed on the package exterior surface by reaction of the etchant solution with the resinous material. A waste outlet and reservoir extends from the etch head. The etch head is attached to an alumina ceramic heat exchanger including a spirally grooved passageway formed by an inserted core to heat a small volume of etchant immediately prior to introduction of the etchant against the package and subsequent oscillation.