| ??? 01/25/07 18:48 Read: times |
#131483 - O-Who? Responding to: ???'s previous message |
Joseph Hebert said:
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. I hope you didn't get hit by the recent ice storm too hard. That looked pretty ugly from down here. We just worked from home for a couple days and it was over. I'm north Kali refugee, so I'm used to both 6 months a year of 40 deg/F (~4 deg/C) weather, and the taxes are quite a relief in comparison. The Texans are working at thining my blood with 9 months/year of 95+ deg/F (35+ deg/C) heat, but it's going to take some time. My wife has a bunch of family up there, she's part Cherokee. We live in Longhorn country, so I'm going to throw back a "O-Who"? :-) Joseph Hebert said:
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 I first came across it as a ham radio op interested in microwave techniques. I was playing around with stripline MMIC amps in the early 90's. It was a real eye opener for me, and taught me quite a bit about signal propigation on a circuit board. What's really funny is the whole prototyping process seems so much easier now than 1983/84 when I learned to make PCB's. We used to hand layout/draw with rub-off sticker traces and resist pens. It was an agonizing process. Now we have almost free schematic capture software with layout editors and autorouters, laser printers, and cheap mail order boardhouses. IMO, the thing that keeps the hobby/amateur sector stuck in the 80's is familiarity of old techniques, and the ubiqutious "junk box". I have a "junk box" collection of old obsolete thru hole parts that just proves too tempting when it comes down to "open wallet" or "make due". In business it's just the cost of doing business, or the NRC entry cost of a project. It creates a kind of mental inertia when it's your lunch money. I'm planning on ordering a big batch of surface mount caps and resistors to help me overcome this. I think I'll get some SMT '51's and 74HCT logic and save the bent leads for things like op-amps and voltage regulators. |
