Howdy Rob,

How's the weather down there? I spent a dozen years in the Dallas area, which is why I now spell and pronounce the state name with the vowels transponsed, Taxes.

What you say is true, but the original impetus behind surface mounting parts was not to save board space or increase part density. The original, the very first, surface mounting of parts was, as is evidenced in this very thread, a means by which engineers and technicians building prototypes could simplify board construction. It allowed them to drill fewer holes, and work on a single layer instead of two. And because it was a truly brilliant idea, other justifications soon became evident. Someone realized that particularly long headers and high pin count chips produce perforation weakend fault lines along which boards were subject to fracturing. SM techniques eliminated these perforation lines. Some anonymous RF engineer quickly realized that by eliminating the leads from discrete components he could eliminate wads of stray inductance and capacitance. Do you remember that the MELF package was the precursor to the 0805?

The desire for increased parts density, and the associated scale reduction, was a secondary, or at best parallel, impetus behind the development of SMT. PGAs, not BGAs, were developed to increase the pin count per unit area of board space. No, miniaturization was the natural evolution of a newly established technology, not the impetus behind its advent.

Joe