At 05:35 AM 11/19/2003, Leo Potjewijd wrote:
At 19/11/2003 01:09, Abd ul-Rahman Lomax wrote (among other things):
[a list of assumptions]

I must say that these statements are not entirely correct: many SMD connectors need holes in the PCB for positioning or letting the mating part through.
I regularly use a <http://www.avx.com/docs/Catalogs/6207.pdf>FFC connector that has pegs for positioning and strain relief. You will need two non-plated holes in the PCB to accommodate that thing.....

First, what I wrote were presented as simplifying assumptions, not as necessary truths. Secondly, you need the holes, but you don't necessarily need a pad. Protel will allow you to use a via. However, there is no provision for an "unplated" via, so one might need to manually ensure that a via with hole size exceeding the diameter is not plated.


This isn't very satisfactory, however, because it would involve modifying footprints just so that report generation would be a little easier. Better to generate reports for all three logical types (pure SMT, pure through-hole, mixed).

Note, however, that there is an additional complication, which is that there can be a "component" which is neither SMT nor through-hole, it is a non-assembled device for accomplishing some purpose other than providing a place for assembly. It might be a test point, it might be a component with no holes whatever, representing something not fastened to the board but to, for example, an adjacent board, and one wants to place a dummy footprint and lock it in place to keep the space clear.

The most likely reason the fab house asked for the pincounts is calculation of the bare PCB price (at least, my boardhouse does use this info for that purpose): holes need to be drilled, many different sizes and/or really small ones result in greater setup/machine/handling time.
In electrical testing, SMD pads most likely need a different test setup: thru-hole pads can be accessed on both sides of te PCB while SMD pads can not, SMD on both sides will thus result in higher cost.

The question was directly posed by Mr. Malik and it was explicitly about "an add-on utility or a process script that can separately count the number of SMD and Through-hole components."


It's not likely Mr. Malik was asking in response to a fabricator query, because fabricators have little need to know the number of surface pads; surface pads are merely copper features and openings in the solder mask; however, if the question was about pads, he asked the wrong question. It's easy to get a pad report, use Edit/Export to Spread.

I do notice that Advanced Circuits asks about SMD pads in their instant quote form. Oddly enough, they *don't* ask about holes and the variety of hole sizes, which would have a larger effect on price, I'd think. However, I do recall a conversation in which a fabricator stated that holes have become so cheap to drill that they are not a substantial contributor to cost....

Mr. Malik, on the other hand, made another inquiry seeking recommendations for assembly houses, and I'd expect an assembler to need the information for a quotation; it's common to see figures of so many cents per SMT component and so many per through-hole component....

For this, the information would not need to be absolutely accurate, and the existence of a few ambiguous components would have little or no effect on the cost.



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