Sounds like you have a pretty good idea of the process already. Without knowing the nature of your design -- surface mount, thru-hole, frequency, size/temperature/environmental restrictions, etc -- here are a few tips on my watch list. Hope they help. Drill sizes: Many board houses offer several "standard" drill sizes. If your design uses drills that are not on this list, you will incur an additional charge. Check with the board house. Clearance constraints: Board houses guarantee a minimum clearance between separate copper. If their guananteed minimum is 0.008 and you've designed traces that are just 0.007 apart, your board's production may be held for intervention, or these traces may be 'bridged' on the final board. Usually not a big deal -- you can often just cut them apart with an X-acto knife. Footprints: Confirm that you have used the correct footprints on your design. For example: you may prototype with a sample chip in an SOIC-20 package and design your board with that footprint. When it comes time for production, you might realize that the SOIC-20 package is scarce with large lead times, while the same chip in a SSOP package is readily available. Basically, check price and availability before settling on a footprint. Test points: When designing the prototype board, make room for testpoints on any signal that you may want to monitor when debugging your design (as long as they don't affect circuit performance}. I've designed footprints for every microcontroller that I use, with dual-row headers bordering each edge, accessing every pin. This took some extra work, but it is a real help when debugging a MSP430 series microcontroller in a 64-TQFP package. Mechanicals: Make sure everything fits on the board, and the board fits in the case (in every dimension). Sounds trivial, but it's not. Have a friend double-check your design. Are your tantalum/electrolytic caps in the right way on +/- voltage rails? Did you accidentally connect the power backwards?(Throw a diode inline with power, just in case) Are the diodes in correctly? Did you specify 200K when you meant 200R? All simple mistakes, yet hard to find when you have your pride-and-joy, newly-populated board in your hands. Ask for help: Call your board house of choice, plead ignorance and tap any knowledge that comes your way. Also, do a web search for board houses, and search their websites for design tips. You'll find articles on decoupling caps, sheilding, capacitance issues, etc. Hope this helps -- not that I have made any of these mistakes! Shawn >From: Chris Loiacono >Reply-To: pic microcontroller discussion list >To: PICLIST@MITVMA.MIT.EDU >Subject: Re: [EE]: Your thoughts on PCBs from design to production >Date: Tue, 7 May 2002 20:04:09 -0400 > >I think your logic is sound. > >I have a slightly different perspective that may or may not add some >insight: > > >1. I like to proto on a breadboard. If I can get the thing to run without >objectionable noise on a breadboard, there will generally be very few of >such surprises in the final design. I always make sure I am using the same >parts I will be using in the final design before proceeding. > >Assuming that you have all the obvious areas covered, such as number of >layers, minimum trace widths and copper weight for (especially) power and >ground nets; decoupling scheme w/ cap leads close to Vcc pins, mechanical >design considerations and component selections with alternate footprints >for >less-common parts, etc... etc....then > >2. I like to fly through the schematic and layout of proto's. I like to >trust my tools, but also to check the result minimally at this stage. Send >out the gerbers and deal with the one or two problems that may come up in a >two or three pc order. > >3. Fix the proto bugs and implement any new ideas that have come up since >the time the proto design was frozen. Check mechanicals and mounting holes, >etc,..and move as needed. Then run the gerbers again and check the results >with a good viewer several times. I do this with a list of characteristics >that the tool's DRC won't look for. When I feel 100% confident in the >updated board, then it's ready for a production run. (In other words, just >do it!) >You'll know if it's ready or not, and you'll decide accordingly. > >ps: I still like Advanced Circuits because their proto qty prices are OK, >and their production pricing starts at some pretty low quantities... > >Have fun, >Chris > > > > -----Original Message----- > > From: pic microcontroller discussion list > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Byron A Jeff > > Sent: Tuesday, May 07, 2002 2:00 PM > > To: PICLIST@MITVMA.MIT.EDU > > Subject: [EE]: Your thoughts on PCBs from design to production > > > > > > I'm contemplating my first real PCB production run. I know > > that the topic > > has been beaten to death in the forum. I realized though that > > the problem isn't > > a lack of information, but instead a overflowing wealth of > > info. I wanted to > > get your experiences of a wholistic view of the process from design to > > production. > > > > The situation: I have a prototype design done in wire wrap. > > For production > > it will need a few items added, so the design isn't yet > > airtight. In the > > end I'd like to get a moderate production run of say 100 > > boards. The board > > size is going to be somewhere in the 3 in x 3 in to 4 in x 4 in range. > > > > I envision the process in three stages: > > > > 1) Design: finish adding the goodies to the prototype, layout > > a PCB, then > > test and tweak until a rock solid design and board is complete. > > > > 2) Prototype production run where a handful of boards are > > done with the final > > design from the board house, which are then tested. > > > > 3) Final run. The actual production run. > > > > The variables are turnaround time (TT), limiting cost (LC), > > and quality (Q). > > Each of these vary at each stage. Here are my roundabout guesses on a > > 0-10 scale. > > > > Design: TT:10 LC:10 Q:4. This needs to be a quick dirty phase > > because it > > may iterate over several versions. It needs to be relatively > > inexpensive due to revisions. The quality only needs > > to be good > > enough to test. > > > > Prototype: TT:10 LC:5 Q:10. The prototypes should be the same > > quality as > > the production boards. Quick turnaround time in > > order to verify > > the results. Since this step is done once, cost > > isn't a significant > > issue. > > > > Final: TT:3 LC:9 Q:10. For the final run I'd like to see top > > quality at the > > best price. Since everything has been tested, > > turnaround time is no > > longer critical. > > > > What I wanted to see was folks' experiences at each phase. > > What tools did you > > use? Which house did you choose? Why? > > > > There are numerous choices at every stage. Any assistance in > > narrowing down > > the field to fit the criteria outlined above would be helpful. > > > > Thanks, > > > > BAJ > > > > -- > > http://www.piclist.com hint: PICList Posts must start with ONE topic: > > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > > > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > _________________________________________________________________ Join the world s largest e-mail service with MSN Hotmail. http://www.hotmail.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads