PCB design software - Page 1
Forum section: electronics / general

author: akis
author_rank: Frequent Contributor
timestamp: May 10, 2014, 07:12:49 pm
content: I have asked something similar somewhere some time ago.Is there any software that takes a schematic plus the dimensions of a board, maybe with a few "locked" items (eg connectors, bulky components) and then be able to place everything on the board so reasonably that it can then be routed (automatically of course) ?I have found that so far I have to place manually every single component resulting in a lot of aggravation and stress, it is the most hated part of any design I try to make. As there are almost no rules to follow it is not like designing a schematic it is so free and loose that it is an iterative process of trial and error, place - route - move - route, the poroblem being there are like 100s of iteration steps with half-routed boards and components that need to be moved else it cannot be routed and arghhhhh.

author: Pasky
author_rank: Regular Contributor
timestamp: May 10, 2014, 07:15:12 pm
content: I think all PCB design softwares have an autorouter, but none are really any good.Probably the closest thing you're going to get.

author: trevwhite
author_rank: Frequent Contributor
timestamp: May 10, 2014, 10:12:00 pm
content: EasyPC has autoplacement and auto routing but I never trust such things.

author: zapta
author_rank: Super Contributor
timestamp: May 11, 2014, 04:26:48 pm
content: Quote from: akis on May 10, 2014, 07:12:49 pm

author: larry42
author_rank: Regular Contributor
timestamp: May 11, 2014, 04:46:51 pm
content: Not as far as I know - all teh professional layout ppl (and and a part-time layout person like myself) do it by hand, even on 20+ page schematics.Most proper SW allow you to select / highlight components between the schem & layout.Oh - and noone I know uses autorouters.

author: akis
author_rank: Frequent Contributor
timestamp: May 11, 2014, 05:29:45 pm
content: Quote from: zapta on May 11, 2014, 04:26:48 pm

author: Jeroen3
author_rank: Super Contributor
timestamp: May 11, 2014, 05:54:46 pm
content: Quote from: akis on May 10, 2014, 07:12:49 pmThere are many rules regarding placement. But these change per component/signal. Some datasheets even have a placement/routing checklist.However, placing and routing a pcb is a puzzle, but the difficulty isn't that high if you have enough board.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 11, 2014, 06:05:50 pm
content: Correct placement of components is part of the design process. It can't be automated.The computer doesn't know enough about the design to be able to work out exactly where each component needs to go. It doesn't know what currents will be flowing where, which nodes are sensitive and which are noisy, or what the external stimuli will be. It would require detailed, device-specific knowledge of decoupling, and transmission lines, and EMC, and parasitics, and loop stability.Moreover, it would take just as long to check that each and every component is correctly placed as it would take to place the parts manually - so there wouldn't be any commercial benefit to having such a feature anyway.

author: free_electron
author_rank: Super Contributor
timestamp: May 11, 2014, 06:07:16 pm
content: Quote from: akis on May 10, 2014, 07:12:49 pmreally ? it's the most fun part !

author: akis
author_rank: Frequent Contributor
timestamp: May 11, 2014, 06:10:10 pm
content: Quote from: free_electron on May 11, 2014, 06:07:16 pmOK I will send you the schematic and the board outline in Diptrace - you would try to do it ?

author: con-f-use
author_rank: Unknown
timestamp: May 11, 2014, 06:20:00 pm
content: If something like thetravelling salesman problemisNP-hard, I'd assume an algorithm to do auto-placement and auto-routing is at least as hard.

author: scientist
author_rank: Frequent Contributor
timestamp: May 11, 2014, 06:50:46 pm
content: KiCAD does autoplacing. You've got to manage layers/sides and mounting angles, though.

author: hagster
author_rank: Frequent Contributor
timestamp: May 11, 2014, 07:05:19 pm
content: What would be interesting is an autorouter backed up by some serious supercomputing grunt that could update the autorouting live as you drag components about.

author: georges80
author_rank: Frequent Contributor
timestamp: May 11, 2014, 09:03:11 pm
content: Given that most real designs will have connectors, indicators/display, power jacks and have to fit into a box that may have 'interesting' dimensions and mounting holes etc, hand placement of components is unavoidable. Any design that has analog/power/digital with any performance requirements means placement of components is critical.No boards that I've design have ever been auto-routed. Professional contract layout people have always hand placed and then hand routed. Power circuits need planes/thick traces/flooded traces which must be hand done. High speed signals (differential traces etc) need to be impedance matched. DDR traces need lengths matched. None of this stuff can be effectively autorouted. Multilayer designs have all sorts of ground plane/cut requirements to ensure they don't compromise routing of high speed signals on the other layers.So, auto-routing is only marginally useful for low tech/simple designs and no mainstream EDA company is going to waste resources trying to do that when they know the tool won't be used for any larger/critical design since a good layout engineer can do a much better job in just a few days with a little guidance by the design engineer.cheers,george.

author: sleemanj
author_rank: Super Contributor
timestamp: May 11, 2014, 10:41:29 pm
content: Diptrace does auto placing. Place the stuff you care about on the board and lock them, then auto place the rest. Doesn't do a brilliant job, but it's there if you are super in a hurry.As for autorouting, I hate routing, boring annoying work. Route the important bits then let you favourite auto do the menial labour I say, give it a once over and manually reroute anything very silly when done.Sent from my HTC Dream using Tapatalk 2

author: Dago
author_rank: Frequent Contributor
timestamp: May 12, 2014, 08:52:16 am
content: You do NOT want the software to do autoplacing or autorouting. The software just does not have all the information needed to make educated "guesses" on where the components should go. Like someone said it's part of the design process. There are plenty of "rules" how you should place your components on the board.There are proper autorouters but they are mainly for extremely complex designs requiring delay matched lines etc. where you need to enter a ton of information regarding the routing for the router to do a semi-decent job. For anything simple (this applies to 99.9999% hobbyist stuff) you do not want or need an autorouter. Newbie mistake nr1.

author: sleemanj
author_rank: Super Contributor
timestamp: May 12, 2014, 01:06:41 pm
content: Quote from: Dago on May 12, 2014, 08:52:16 amFor most hobbyist stuff it matters not a bit how it is routed.Not using all the tools at one's disposal is inefficient.Sent from my HTC Dream using Tapatalk 2

author: Dago
author_rank: Frequent Contributor
timestamp: May 12, 2014, 01:13:32 pm
content: Quote from: sleemanj on May 12, 2014, 01:06:41 pmThat is true as well but it is not an excuse to not learn how to do it properly.

author: Kjelt
author_rank: Super Contributor
timestamp: May 12, 2014, 01:57:09 pm
content: If you manually route the power, clock and other critical nets and have a simple (read: non RF or EMC susceptible) design there is nothing wrong with letting the auto router doing some of the routing as long as you can undo it when it screws up, which happens 9 out of 10 cases. I would suggest to route everything manually.

author: akis
author_rank: Frequent Contributor
timestamp: May 12, 2014, 02:15:14 pm
content: We are discussing placing and routing. Placing is the most important because it will determine the elegance of the routing. I believe Diptrace tries to minimise the total route lengths by trying combinations of placements - and this is almost how I do it by hand, after specific components have been placed and locked in place, eg pots, jacks, transformers etc. The big problem is that Diptrace's auto placement is very, very slow, 100% CPU, only one CPU (even though I have eight), and it takes ages as an iterative process of place - route - undo - place - route - undo, either by hand or by a combination.I was looking for software that might be quicker / take advantage of CPUs so that the iterative process becomes actually useful.This is my nightmare board, it's the largest dimensions that will fit in the box and even so it sits over another board, have to use all available space. I have simply placed everything according to the ratlines trying to shorten distances, however routing will be impossible as they are so close.

author: zapta
author_rank: Super Contributor
timestamp: May 12, 2014, 02:20:33 pm
content: I use the eagle auto router on all my board and found it to be very useful. I first route manually the critical nets and than let the auto router so it's magic. The results are very reasonable and if not I fix manually (mostly for aesthetic reasons).AFAIK, eagle doesn't do auto placement, otherwise I would do the same for placement.If it works it works.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 12, 2014, 03:29:22 pm
content: You've made a rod for your own back by using through hole components.Swap the R's and C's for surface mount, and the problem goes away.

author: akis
author_rank: Frequent Contributor
timestamp: May 12, 2014, 04:32:30 pm
content: 0.25W SMD resistors are the 1405 (3614) types, which is 3.6 mm across including pads and 1.4mm width. How on earth am I going to solder these on a board?

author: nctnico
author_rank: Super Contributor
timestamp: May 12, 2014, 04:41:32 pm
content: Quote from: sleemanj on May 12, 2014, 01:06:41 pmBack in the through-hole days I used the autorouter a lot for DIP packages and 2 layer boards. It did take me a while though to get the autorouter setup so it would route a board properly.With SMD you need to do so much planning that it will take a significant amount of time to learn how the autorouter works. In my experience it usually takes 3 to 4 times more time to get the components placed than it takes to route the traces. I always say: most of the time that goes into a PCB design is spend on putting the components in the right place.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 12, 2014, 04:42:50 pm
content: Quote from: akis on May 12, 2014, 04:32:30 pmYou're kidding, right?

author: akis
author_rank: Frequent Contributor
timestamp: May 12, 2014, 06:22:49 pm
content: No I am not joking, I have no experience with soldering SMDs and from what I see it requires at the very least a solder mask (which I am not producing on my home made PCBs), and special handling to avoid bridging, so I am naturally apprehensive.But I could use the 0.4W SMD resistors which are slightly larger at 6.1mm across - easier to handle with normal soldering iron tools.

author: nctnico
author_rank: Super Contributor
timestamp: May 12, 2014, 07:05:38 pm
content: Soldering SMD is easy. Just be sure to use flux, a tip which looks too big and set your iron to 330deg C. The right temperature helps to keep the flux active for a long time, the big tip provides enough heat to make the solder joint before the flux stops working. Bridging is a problem caused by the wrong temperature and a tip which is too small. I'm soldering 0.5mm pins with a 3mm wide tip. Actually I'm soldering several pins in one go.

author: georges80
author_rank: Frequent Contributor
timestamp: May 12, 2014, 07:33:39 pm
content: Quote from: akis on May 12, 2014, 06:22:49 pmSolder mask really isn't needed for a prototype etc.Here's a board with a bunch of 0603 R's and C's and also a few QFN/DFN packages. Lead pitch on the IC is 0.5mm. FLUX is the key. No need for a tiny soldering tip - flux/solder surface tension does most of the work for you.Don't let the fear of SMD get to you, it's actually quite easy to deal with by hand. Solderpaste/hotplate helps, but a regular soldering iron (not some junk one), some decent solder and flux and it's easy. I have used thruhole stuff for many many years - other than connectors and some passives that are leaded by their nature.cheers,george.

author: akis
author_rank: Frequent Contributor
timestamp: May 12, 2014, 07:42:07 pm
content: There is no solder mask to isolate those closely spaced tracks and they appear to be soldered - how did this NOT bridge? I have seen some youtube clips but in 50% of them they DO bridge and then you have to remove the IC and use solder pump and so on ? The other 50% I watched worked first time, as if by magic, no bridging.

author: con-f-use
author_rank: Unknown
timestamp: May 12, 2014, 07:50:10 pm
content: How do you solder QFN/DFN packages with just an iron and flux?

author: georges80
author_rank: Frequent Contributor
timestamp: May 12, 2014, 08:02:21 pm
content: Flux is the key to prevent bridging and only a clean tip with a SMALL amount of solder on it is needed.Hot air tool for $90 easily will take care of QFN/DFN parts if they need their thermal pad soldered.If components are on one side only (often the case for the SMD boards I make), then a hot plate ($50 on ebay) is great for reflowing.The board in the picture I posted was done with a soldering iron, flux and a hot air tool to reflow the QFN/DFN parts.cheers,george.

author: scientist
author_rank: Frequent Contributor
timestamp: May 12, 2014, 08:18:48 pm
content: By using leaded solder, fine iron tips, and a truckload of flux.

author: sleemanj
author_rank: Super Contributor
timestamp: May 12, 2014, 11:35:08 pm
content: Hand soldering 1206 and 0805 size parts is easier than through hole, with or without mask.Apply small mound of solder to one pad, pick up part with tweezers, put iron on end of tinned pad and get the solder melted again. Slide part in so it butts against iron tip, remove iron and let solder harden, rotate board and solder other end, job done.Sent from my HTC Dream using Tapatalk 2

author: zapta
author_rank: Super Contributor
timestamp: May 12, 2014, 11:43:11 pm
content: Quote from: akis on May 12, 2014, 06:22:49 pm1406 are giants! I am serious, and I don't have a microscope or a 16 years old eyesight. If you haven't tried yet you should start now ;-)You will need a good solder iron or use solder paste and stencils (e.g. OshStencils.com, pick the 5mil version) and then reflow with hot air, toaster over, hot plate, etc, you can find plenty of material on youtube. You should not have trouble soldering 0805 or 0603 by hand, it's just learning the technique (youtube is your friend).

author: Dago
author_rank: Frequent Contributor
timestamp: May 13, 2014, 05:40:49 am
content: Quote from: con-f-use on May 12, 2014, 07:50:10 pmYou just basically swipe the pads with the iron (with plenty of flux) and you're done.Soldering SMD stuff is easy. I can't fathom doing electronics as a hobby in 2014 without being able to solder SMD. Basically the only components you CANT solder by hand or with a 100$ hot air station is BGAs and some more obscure packages.

author: Rick Law
author_rank: Super Contributor
timestamp: May 13, 2014, 05:57:03 am
content: "Practice, practice, practice. Practice makes perfect."That was what my high school algebra teacher used to say (RIP).I had a charge board with an on-board 78L05 (SOT-89) that smoked the first week. It melted itself off the board along with the decoupling cap. . The dealer replaced the board, but I had in mind fixing the bad one someday. That remained a fantasy for some time.I initially started some practice with an old PC motherboard - bad choice. I had a lot of frustration and fruitless days. I couldn't even get a couple of through-hole jumper pins out even after switching to a 60W iron. (I later realize it must have been the damn ground plate.) I was so scare of it that I couldn't even imagine trying to take the trimpots out of the charger board (to gain access to the 7805 area) without melting the damn thing onto the board.Well, right here, reading some of the posts, I learn about the ground plate and how it affects soldering and I realized that must have been the issue. So, I re-approached the task with gusto.I found an old Startac phone I had (a pair of them). I desoldered and resoldered some of the IC's (0.4mm) and resistors. I did that over and over just to observe the resulting solder joints. (I likely cooked at IC the first couple of times I desoldered and resoldered). I was not concern about it working. I was merely practicing how I can do a good soldering joint quickly to avoid cooking the real thing. What angle is best, which tip to use and what results I get, so forth.I must have resoldered each of the half dozen 8pin SMD IC's 20 30 times each.A few times, I had the resoldered IC joints looking almost factory like. And most times (well, about half the time) I can complete the 4 pins resoldering (on one side of the 8pins/0.4mm pitch IC) within a couple of seconds so I think it would have survived "thermally". After a while, most times, I get the whole 8pin/0.4mm resoldered within 10 seconds including cleaning up any bridging.After a while, the 1mm pitch IC's looks down right huge!I still have problem finding those 1mm-end-to-end sized resistors after I desolder them, so I didn't get good practice with them.Not that I consider myself good at it, but SMD soldering no longer looked likean unapproachable task.I did successfully repair that charger board which I use as my power source for most small experiments on breadboard. I removed all the trimpots (3) without melting anything and gained access to the 7805 area. I ended up using a TO92-78L05 I have at hand, bend the leads to fit the SOT-89 and soldered it on like an SMD. I did the same with the melted-away decoupling cap. I replaced the three trimpots with new ones since the trimpots doesn't have that many turns in their life. I added another power-on LED because the original is at a bad spot to be seen. The whole thing works. In fact, I put away the replacement board the seller send me, and use my repaired one just because I repaired it.That was a very good day. I was so pleased with myself for something so simple - it was down right embarrassing. But, I was pleased.As I say, I don't consider myself good at it. I think I have at least 50/50 chance of getting working end results now.Taking away the fear and making the task approachable were the important parts.The Startac phone is still on my soldering table - ready for more practice sessions. When I am reworking a board, I at times start with a few practice before I dig into the real board I want to work on.