| | Hi, | | | | To improve the Design For Manufacturing I am currently looking to write down some design rules that can (and should be) used by our engineering department. | | | | Can somebody help me get started or give some usefull tips on where to find a reference work where I can start from. | | Maybe there is even someone out there that is willing to share his design rules with me. You can always e-mail those to : | | philip.bautil@alcatel.be | | | | Thanks in advance | | | I received your email not realizing this also was you. What the others have said is true concerning IPC being a firm foundation on which to build from guidelines to make them rules. Notice I said guidelines and rules. Guidelines are just that. Your company, and its designs/product, requires rules with which to affect DFM. | | I also would like to comment on DFM. Without CE (concurrent engineering), it is nothing. Concurrent engineering provides the ability to include all "experts", in various areas of responsibility, from concept to customer acceptance. CE is the heart of it all. | | I work with many companies throughout the world developing rules to ensure processes are managed instead of results. Rules are meant for strict adherence while ensuring new ones are developed from R&D, and guidelines based on it, to ensure initial quality and long term reliability is effected. | | If I uderstand you correctly, it is the fabrication process in which you are interested - not necessarily assembly. To this end, I will provide you my PCB fabrication master drawing notes, used at one of your Alcatel affiliates within the last two years, that may be turned into acceptance specifications over time. | | Enjoy, | | Earl Moon | Phil,
The DFM of a board is a critical thing and there are lot's you can look at. As earl say's IPC is got to be the bible for everyone but over and above that there are thing's that aint in there that come along either because of equipment you use or the way the design or board is done that you need to improve. Examples..
The board shape. you will alway's have someone sitting in a little dark room comming up with a sexy new board shape with 5 or 6 sides, a few curves n so forth, then figuring out how to get the circuit on to it. Ok so I'm exagerating..or am I..... The point is..rule No1 should be..make that dam thing a rectangle, it's easy to fit it down a surface mount line for a start. it you cant get it rectangular then get some breakout tab's on it to make it rectangular. If you do have a break out I'd say use a V score instead of nibble tab's cos the tooling cost for breakout tool's will be cheaper. remember that your gonna have to run it down a smd line using a conveyor so make sure there's at least a 5mm gap around the edge so you can get a grip on the board no paste. Ground Planes..if your gonna have them ..manage them, cross hatching, break em up around the board to distribute the heat. Components, can you combine any..resistors into a resistor net? and so forth. Stear them away from thing's that you know you'll have problems with, melf's are a personal hate of mine...round thing on flat surface..urrgh. Fin pitch devices like 25thou pitch..can you get a BGA alternative, the cost of the BGA package is plumeting so it's gonna become far more run of the mill, the defect's per mil is something like a quarter of those of a QFP,so if you aint in it today..you better be thinking about it tommorrow. Think about the processes down the line..Wave for instance The direction of the chip's and other devices that are appearing on the bottom side, although the best idea is just dont put anything there unless you have to. Connectors..get them in the same direction so your designing in the flow of the board thru the process. Solder thief's are another great thing, use them as much as you can at the back of connectors, front n back of SO's, QFP's and so on. Another thing you can look at is the design of the solder mask. Remove all the mask from the bottom of connectors execpt where there is some tracking and your greatly reduce the risk of shorts' and eliminate the non random solder ball's. Use the mask on the fine pitch stuff to shore up the solderpaste to reduce shorts. Think about your vision systems..placements machines, printers even inspection machines, not forgetting the human operators. The colour of the mask can be a big help in being able to spot the defect's...not that you'll have any cos your DFM is so hot. These are just a few of the thing's that you can do, there is load's more. I had an argument with someone the other week about DFM, Yes it's for the customer's benefit since it will give them a better finished product because you can build it easier, but, and this was the disagreement, it's also for you. Your the one whose building it and your profit's rely on you being able to do it quickly and hassle free so you meet what ever margin's you've set. I have to say I love doing DFM's..get's the grey matter running, and if your doing it as a service..you can even charge decent money for it....but dont forget the disclaimer!!!
JohnW
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Hi,
To improve the Design For Manufacturing I am curren...
- Jun 01, 1999
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