I have not read this entire thread, but at risk of showing my lack of understanding, let me make a few comments.
--- In [email protected], "Frank Bennett" <[EMAIL PROTECTED]> wrote: > > Adding a vendor part number (VPN) field (F3?) would enable an improved > BOM listing. This field would be optional and would show up in the > BOM if present. The advantage of a VPN nails down a symbol and > footprint. Selection of a VPN defines a specific footprint while the > schematic symbol could look like anything the schematic designer likes > as long as the pinout is consistant. A VPN enables future creation of > a project (or board) only BOM (or library) and could reference a > larger company wide parts library (or database). Without this each > designer potentially re-invents a symbol/footprint library for each > project. I'm not sure I follow the connections you are trying to make, but I am currently using a package that lets me add VPN as well as other fields to each part on the board. I have not integrated this into a database. The lack of a database connection greatly limits the utility and can significantly increase the work required to make this work. > Example: > part # symbol sect footprint ref manufacture description > --------- ------ -- -------- --- ----------- ----------- > DM74LS00N 7400 A DIP14 (or N14A) U1 > DM74LS00M 7400 B SMP14 (or M14A0 U2 > 54LS00W 7400 A W14B (or CFP14) U3 > Note: this is 3 separate parts and need separate ref designators > (Using similiar but different parts can happen) Like resistors... > Parts with multiple sections only count as one part in the BOM with > a shared footprint, the section letter would not be listed. The > manufacture, description, inventory could be added to a future, > separate parts database, selector, navigator.... This is where it gets interesting. One thing you have left out is that often there is not just *one* part that can be used in a given socket on the board. I'll discuss this more below. There is also the issue of build (or stuff) options. A single schematic can cover several different build specs where some parts are substituted, added or left off as options. Its hard to deal with this without a database. > The bottom line is the schematic should be the master controlling > document...need to swap parts, pins or change footprint? - update > the schematic and re-generate the netlist. I don't really agree here. I can use a 74LS00 (your example above) from TI or Philips as long as they have both been approved. The selection is up to the buyer, the engineer no longer needs to be involved. Rather than the BOM including specific manufacturer's part numbers, many parts need a company part number which then refers to a number of approved parts. When an optional resistor is left off of the board or has a value change for a slightly different application, again, as long as this is an approved change it does not need a new schematic or netlist. The schematic tools should be flexible enough to support generation of multiple BOMs from one schematic given selected options. > A more complicated parametric example: > > Digi-Key Part Number FC0603-50BFTR-ND > Manufacturer Part Number FC0603E50R0BTBST1 > Symbol: R > Description RES 50 OHM 125MW .1% 0603 SMD > Manufacturer Vishay/Thin FIlm > Resistance In Ohms 50.0 > Power (Watts) 0.125W > Tolerance 1/8W ±0.1% > Lead Style Surface Mount (SMD - SMT) > Case 0603 (1608 metric) > Packaging Tape & Reel (TR) > Composition Thin Film > Voltage - Working * > Temperature Coefficient * > Quantity Available 1 > Minimum Quantity 1 > Unit Price USD 0.91000 > Datasheets > here there are many resistors with a common shared symbol and footprint > > As a designer why do I want to deal with all this? > Ans: To make sure the correct parts are ordered, your board is > built right, it will work properly and save the company money > by ordering common parts in quantity from a qualified vendor. In the above, there is not only a manufacturer's part number field which will change depending on available parts, but also a disti's part number which can change depending on the packaging you order, reel, cut tape, tube, etc. Then even the disti is included which can also change (if I am ordering these parts from Mouser, why not give them the entire order?) (btw, you are paying too much for your resistors ;) The design I just got into prototyping had several last minute part number changes because of supply issues changing between the engineer (me) selecting the parts for the final BOM and the buyer (me) placing the order (about 1 week). It would be counter productive for management (me) to require the engineer (me) to change the schematic just to make things easier for the buyer (me).
