See below
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Randy McHugh
Optimum Design Inc.
266 Corporate Drive
Madison, WI 53714
Voice: (608) 243-9418
Fax: (608) 243-9420
Email: [log in to unmask]
Gentlemen,
Thanks for the response... Hope youlle be patient coz I have lot of questions for you...I am a bit confused... Im just new in the business (about a year) . I need some you...
1. I see that in IPC-SM-782 there are specified conductor thickness with regards to routing grids... Pls. correct me if Im wrong.. I specified in my DFM that Table 3-1 of IPC-D-275 is also applicable to SMT since 275 in general discusses all types of board technology (THT/SMT)...
>>> Yes, those are good "rules of thumb" for thickness'. However, sometimes you have to shave off the trace widths or lessen the clearance to get more traces on the board.
2. I am a quite confused with the use of the grid system... Is there a general grid system for THT (100 mils ?!?) and SMT components ??? I use a general grid of 20 mils for pure THT designs (component placement and routing)... is that correct ??? I havent started with SMT design coz' Im confused about using the routing grid for components... Can you give me a sample (very plain) of how to place then route the wires from the components...
>>> I'd recommend placing the components and routing traces on the biggest grid you can. The bigger the grid the easier it is to manipulate the components. Just remember that you want to use a grid that is divisible by the largest grid on the board. (IE if you placed on a 20 mil grid you can route on a 10 mil, 5 mil, 2.5 mil and 1.25 mil grid, if you placed on a 100 mil grid you can route on a 50 mil, 25 mil, 12.5 mil, and 6.25 mil grid. The latter making for easier routing.)
3. Is the rigid board gonna be obsolete ?!? Just curious because of the technology rapidly growing...
>>> Never, simply because you will still need access to connectors and front panels. It is cheaper to use the rigid board for mounting connectors instead of going to a flex circuit or cable to a hard mounted connector.
4. Is the term single-sided PCB with 2 layers the same as double-sided ??? Is there a single sided board with an inner layer (ground or power) and is it different from double-sided ???
>>> Single sided (normally) means parts on one side, double sided means parts on both side, independent of the number of board layers.
5. I dont know how to calculate for the RF leakage,EMI. that sort of things ...Can you brief me on this...Pls. give a sample...
>>> The best way is to buy a book. (Or IPC spec)
6. If I follow the IPC standards, what is the reliability of my design ???
>>> Depends on how good of a designer you are. I can design a board 100% to IPC specs and yet have it fail down the road due to manufacturing errors or EMI/EMC problems.
7. Isnt it that in IPC-D-275, there are different routing
techniques for analog and digital areas... Analog " power and ground traces placed last " Digital " power and ground planes first "... Must that be followed always... And how can I consider that this area is now the digital or analog area... Does it also mean that I have to separate, have different terminals, for the power and ground connections for analog and digital ???
>>> Again, It's rule of thumb. We have one designer here that specializes in high speed digital designs, I specialize in analog and high power. I route entirely different than him. One point that I rarely hear is good placement makes for great routing and bad placement makes for NO routing.
8. Is air gap and Trace spacing same ??? I saw that for air gap measure is taken from end of trace to end of another trace... while in trace spacing, measure is taken from center to center of a trace, its like measuring its pitch...am I correct ??? WHat will I follow ?
>>> Normally you measure clearance from edge to edge. Center to center came from the grid based algorithms when you knew if a 12 mil trace is place on a 25 mil grid and the next trace is placed on the 2nd 25 mil grid you'll have 13 mils between traces. Knowing this you don't need to measure the edge to edge you can trust the center to center to be 25 mils.
9. Are footprints for all PCB softwares the same (standardized) ???
>>> NO!!!!!!
10. Any good websites for SMT(Rigid and Flex manufacturing and assembly) learning/information ???
>>> Again, I recommend a good book or the IPC spec.
Thanks for your support... More power to the Council !!!
Regards,
Engr. Jay Bitanga
Value Engineer
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