--- In [email protected], "Rick Collins" <[EMAIL PROTECTED]> wrote: > > I have not read this entire thread, but at risk of showing my lack of > understanding, let me make a few comments.
Rick, This is a new thread I just started, thanks for the feedback. My intent is to get us developers to think about changes to KiCad that in my mind are not astronomical... > > --- In [email protected], "Frank Bennett" <bennett78@> 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 ;) yeah, I just cut and pasted this from a quick Digikey search. This data example shows that Digikey in general, has done a great job in expanding the manufactures part number to a unique Digikey one...The problem is that every company/distributor has created their own part number, yes that allows multiple sources of approved vendors, maybe with inventory and pricing but decoupled from the EDA schematic capture and PCB layout. There is no universal part numbering database to describe the part that is needed for the design under consideration nor is there really a need for one. The number is only convenient for describing the group of vendors and each vendors unique but compatible part number. > > 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). Since the schematic/PCB tool is usually decoupled from the parts database my minimal goal would be to minimize the communication between the engineer and procurement. Each engineer needs to look up the manufacture spec then make/find a schematic symbol and PCB footprint for the design then the component guy has to figure out what part the engineer is talking about....lot of room for mistakes: wrong part and/or wrong footprint and/or wrong power or precision.. Web sites like "partminer.com" and new EDA tools can make this bridge easier. >
