Freelance Client Looking For Specific PCB Fab (Is My Client Out Of His Mind?!) - Page 1
Forum section: electronics / general

author: tokyoscarab
author_rank: Newbie
timestamp: December 08, 2023, 08:30:53 pm
content: tl;dr - just read the 3rd paragraph on downHi, I'm an EE who has worked as a full-time freelancer for the past 6 years. A current client of mine wanted a custom PCB made that is an expansion board to a motor driver controller. I have made the pcb to the requirements they had stated up front. So I send screenshots in Altium of what I have and the client has a very strange request. They're not happy with the aesthetics of how the board looks. I could understand this if this was a thing that was going to be a commercial product and put into production, but this is (as far as I know) a one off prototype board for a project he's funding in some capacity. This is also going to exist in a metal enclosure of a piece of machinery that will never see the light of day. Before I get into what his problems are with the design, let me give you some info on what this board needs to do. It fits into two pcb interconnects on the motor driver control board. The client wants this custom expansion board to be able to handle up to 45 VDC at a max of 35A at full load. This is well within what the motor controller board can deliver. The maker of the motor controller board does provide their own I/O expansion board but it can't handle what the client is wanting it for, so he got in touch with me.So what is his problem with my layout? He doesn't like the fact there are traces on the top and bottom layers of the board. He doesn't have a problem with their capabilities to handle the workload, just doesn't like how they look. This isn't even limited to the power traces, it's all the traces! So he gets back to me and tells me this and I explained to him that due to the amount of current the traces need to handle in the amount of space he wants for this board (which is 102mm x 105mm) they have to be this wide and also stitched together. So he tells me that he wants me to rework the board so ALL traces are in the inner layers of the board and to have nothing on the external layers. I, naturally found this to be an incredibly curious and ridiculous request. I ask him did he want just the signal traces or was it all traces. He tells me all, if possible. I then go on to tell him that it would drive up the cost to have these made exponentially not to mention that I also have concerns with heat building up internally in the board and leading to some sort of failure of the board eventually. He also has some odd concern about the traces only being protected by a layer of solder mask and they could become exposed and shorted(). I then ask what kind of environment is this going to be in. He tells me it's going to be in a metal box style enclosure in a vehicle. I still don't see how this is even remotely an issue as in what reality would you have to worry about things banging into a box you'll otherwise never have to open. After much back and forth, I was able to talk him out of the internal trace idea even though he was able to find places that would do some pretty thick internal copper thicknesses. I had to explain to him that at thicker copper levels, you need to have things spaced farther apart and it would be impossible to have the inner layers converge back to the center. For reference, there is about 50 different traces that all have to make their way back to the center of this board.This leads into what this post is about and where things are at. He then was like, what if we just have really thick copper on the external layers. This would be ok if the pcb interconnects weren't on the board. The interconnects for this are Amphenol 10132797-051100LF. They mate onto the motor driver controller and have a pin pitch of just shy of 8mil. This means that the absolute thickest copper you can really run with this is 2oz in my research into different pcb fab capabilities. So for just over a week now, my client is trying to find a place that will make a pcb that has different copper weights for the top and bottom layers. So normal 1oz on the top and however thick he feels he wants on the bottom. I feel I have already done all the work I was asked to do and just want to get the rest of my money out of this job. Does anyone know of a place that would do such a thing? I, personally, have never heard of such a thing. This is not to say it probably can't be done, but I would imagine it would cost a ton for such a specifically custom thing you want made in a quantity of 5.So for my sanity and to just put an end to this, does anyone know of a place that will actually even offer this service? Also does anyone have a good idea of what I can say to him to tell him this doesn't exist (if this service doesn't exist)? I've watched Dave's stuff for a very long time now and this is what drove me to actually starting to post in the forums. I would really love someone to help end my misery, cheers!

author: meshtron
author_rank: Regular Contributor
timestamp: December 08, 2023, 09:07:06 pm
content: Ugh, that doesn't sound fun. I'm an electronics newb, but have been mostly self-employed for the past 15 years doing contract design/engineering work, have run into these kinds of things a few times.First off - what does your project kickoff/quote document language say? Do you have a document that lays out the requirements for completion? Depending on your desire to continue your relationship with this client, my gut reaction is the best result here is you being able to say "Respectfully, I have completed the work quoted per our agreement. The design changes you're requesting now are both beyond the original scope and contrary to the accepted design practices I've used to produce this design. When my final invoice is paid in full, I will be happy to release all design documents to you so you can find someone to make the aesthetic changes you've requested. In the meantime I'll do some searching to see if I can locate a manufacturer who is willing and able to comply with this unusual request, but I know of none off-hand."Biggest lesson I have learned in years of doing this is good documentation up front about exactly what "complete" and "success" look like make handling weirdness late in the project vastly easier. Good luck, sorry I can't help with the fab questions!

author: bookaboo
author_rank: Frequent Contributor
timestamp: December 08, 2023, 09:13:54 pm
content: I'd point blank refuse and gracefully exit the arrangement at the earliest opportunity. Consulting is hard enough without idiots and this guy sounds like an idiot.

author: ajb
author_rank: Super Contributor
timestamp: December 08, 2023, 09:15:17 pm
content: That's kinda bizarre on your client's part.You can absolutely get different thicknesses on top versus bottom, or even different thickness on specific tracks. I think it's a combination of selective heavy plating and/or laminating additional copper foil, which helps avoid problems with trying to do a deep etch in one step. Some info and examples:https://www.epectec.com/articles/heavy-copper-pcb-design.htmlI don't know of any fabs offhand that do this, but would probably start looking for fabs that advertise heavy or "extreme" copper in general and ask if they can do that sort of thing. Or look for domestic fabs of CMs with lots of pictures of fighter jets and tanks on their website: that's probably a good sign they're used to wacky requirements, and will come back with a price high enough to scare your client into a more reasonable solution. (Or not, and then you get to add a crazy selective heavy copper PCB to your portfolio, which is also cool.)

author: srb1954
author_rank: Super Contributor
timestamp: December 08, 2023, 09:28:03 pm
content: You should also point out to your client that having imbalanced thickness of the Cu layers can result in board warpage which makes assembly of the board difficult, if not impossible, with fine pitch SMD parts and especially BGA parts.If there is any risk of shorts it will first be to the exposed pins of the SMD components rather than to the tracks on the board. A good thick conformal coating should protect against risk of shorts.Other manufacturers of automotive electronics don't seem to have any particular problems with tracks on the outside of the PCB.

author: tokyoscarab
author_rank: Newbie
timestamp: December 08, 2023, 10:24:35 pm
content: Quote from: srb1954 on December 08, 2023, 09:28:03 pmI also thought about potential warping of the board due to the unevenness of the copper used elsewhere. I haven't brought that up, but I think I will.

author: aeg
author_rank: Regular Contributor
timestamp: December 08, 2023, 11:06:52 pm
content: Ask for his input on some other, unimportant part of the design, to get his mind off of the traces. Make the boards with matte black soldermask.

author: coppercone2
author_rank: Super Contributor
timestamp: December 09, 2023, 12:25:27 am
content: he thinks he can fool a x-ray machineanother case of data sheet on PCB being top secret technologygreat way to go out of business too, spend extra money on hiding shit, then the competition, using high energy photons, or possibly just a belt sander, will make the same board, with better thermal performance, at a lower cost. instant win.you don't even need counter fiet parts. just remove the unnecessary layers and you beat out cost at any volume!https://www.harborfreight.com/4-in-x-36-in-belt-and-6-in-disc-sander-58339.html?ccdenc=eyJjb2RlIjoiNTUxMTM4MTYiLCJza3UiOiI1ODMzOSIsImlzIjoiOTkuOTkifQ%3D%3Dits about as secure as the contents of a beef wellington

author: tokyoscarab
author_rank: Newbie
timestamp: December 09, 2023, 12:31:51 am
content: I have already brought up conformal coating as well as matte black solder mask, but no go. I don't remember what was given, but on conformal coating he said that he wanted them to be able to be repaired later. He didn't have much to say when I said they do make solvents that will take the coating off and you can just apply more after the repair.He says he has a "gut feeling" that a "normal board" won't be able to deliver what is needed. In this 4-layer design, I assumed 2oz external layers and normal 0.5oz internal, though the whole thing could just be 1-2oz the whole way through if needed. Using the Advanced Circuits trace width calculator, I put in 5oz since that's what everything basically would add up to. The calculator says 8mm width should do the trick. This allows for a 10C rise in temp. So I via stitch all 4 layers together in a lattice pattern. In theory that should be enough, right? Going up to 1oz internally I think would be enough if the 0.5 wasn't quite enough to pull it out. In my mind, all 4 layers would effectively form a large copper chunk that everything would pass through somewhat evenly. I also assume that any heat build up would disperse fairly evenly. Also for reference, this just has to bridge between the thick power pins on the driver board and the heavy duty connector on the I/O board which are 35mm apart.

author: coppercone2
author_rank: Super Contributor
timestamp: December 09, 2023, 12:34:07 am
content: so the repair for a fried trace is going to go from a standard trace job (copper sheet and epoxy) to digging up main street.because the traces don't fail. i never seen it i swear. especially entombed ones that experience a surge and extra strainand I would seriously consider just getting more copper weight on the PCB because via stitching on swiss cheese is less reliable then a solid piece of copper.when a submerged trace fails it will destroy the substrate around it. when a surface trace fails like half the heat should go up into the air and leave the substrate in much better condition. hopefully it will de laminate and separate itself from the PCB before it explodesits literarly two scenarios1) cut trace with exacto, pry it off, glue on copper, lap joint solder, put some UV cure glue on. maybe do a little bit of ball burr work. tell the truth when you say the repair job is basically as good as the original2) cut out a section of PCB and try to do a board patch consisting of multiple substrates glued in on a little miter with japanese grade PCB carpentry . lie about it being just as reliable repaired. Extra fun when you need to pump epoxy into the substrate with a syringe because the trace explosion caused a large layer delamination. require a x-ray machine to make sure there is no residues between layers to reduce isolation. when the submerged exploded trace condenses a copper short into the gap created between layers. actually just throw it into the trash.

author: wraper
author_rank: Unknown
timestamp: December 09, 2023, 12:42:16 am
content: Give him an ultimatum of him either accepting normal design or GTFO and return him any money that he already paid. Does he actually pay for any of your extra time wasted at hourly rate? If not, think again why are you even trying to please the idiot.