Can one get schematic from a four layer board?

Thread Starter

gombault

Joined Nov 15, 2020
3
Hi all, in late 2018 I contracted a company to design me a board for my product. I paid them a large deposit and they told me I would have a sample unit in three weeks. Well after year I was told that the board will have to be redesigned and the new design will definitely work, when asked how long it will take for a new board I was told because of the virus they can’t commit. So they gave me the 4 layer board design and the BOM file. I had the boards made at great cost and gave them an empty board, the rest went from we are nearly there to only a voice mail. They did not give me the schematic is there a possibility to get that from the empty boards and BOM file? I hope I can find someone that can still use this board for my project.
 

jpanhalt

Joined Jan 18, 2008
11,088
Welcome to AAC.

One should be able to capture the schematic from a board design and BOM, assuming things are labeled. Do you have that design in CAD format or simply printed? If CAD do you know which one? If hard copy, then you should have each layer available. Doing that from a 4-layer board that has already been manufactured would be considerably harder, because the inner layers will be harder to visualize.
 

Papabravo

Joined Feb 24, 2006
15,518
Hi all, in late 2018 I contracted a company to design me a board for my product. I paid them a large deposit and they told me I would have a sample unit in three weeks. Well after year I was told that the board will have to be redesigned and the new design will definitely work, when asked how long it will take for a new board I was told because of the virus they can’t commit. So they gave me the 4 layer board design and the BOM file. I had the boards made at great cost and gave them an empty board, the rest went from we are nearly there to only a voice mail. They did not give me the schematic is there a possibility to get that from the empty boards and BOM file? I hope I can find someone that can still use this board for my project.
IMHO it will be nearly impossible to accomplish this feat. That you paid for a design and got only a board and a BOM is a hard lesson. You expected one thing and got something else instead. You will be better of in the long run to swallow the loss and move one with your eyes wide open.

The slim chance that you might have requires all of the following to be true:
  1. The top and bottom layers have a silkscreen showing the component locations
  2. The interior layers are exclusively used for POWER and GROUND
  3. The traces on the top and bottom layers are visible
Even if you generate the schematic and create a new layout so you can build boards you have no idea if the design is functional and correct. You will have to pay sombody big bucks to understand and debug somebody else's design. This is not a road I would recommend for anybody.
 
Last edited:

dl324

Joined Mar 30, 2015
12,681
In theory, it's possible to reverse engineer the board. Having components marked on the silkscreen would help, but you'd still need to match component designators with component values.

Depending on complexity, it might be easier to start over.

Hope they gave you your money back for their breach of contract.
 

Papabravo

Joined Feb 24, 2006
15,518
In theory, it's possible to reverse engineer the board. Having components marked on the silkscreen would help, but you'd still need to match component designators with component values.

Depending on complexity, it might be easier to start over.

Hope they gave you your money back for their breach of contract.
The TS did say there was a BOM (Bill of Material). Hopefully it contains the reference designator and manufacturer's part number so a good purchasing agent can have distributors run down the parts or suggest substitutes. If there are parts on the bill that need to be fabricated (e.g. a torroidal inductor), then that will be another level of headache. Anybody who has ever tried to construct a working circuit from a magazine article knows the frustration of missing information.
 

Thread Starter

gombault

Joined Nov 15, 2020
3
Hi All, and thanks for your input so far. I can just tell you what I got from them, they gave me the files that I gave to someone that could make the boards. They also gave me the BOM files that should allow someone to make a complete board. I was thinking of having the first boards made in china but luckily it was just before the virus got to our country South Africa so I had samples made locally. I got no money back and going to a layer will just be too expensive. I will try to attach those files I think you guys will make more sense out of them
 

Attachments

WBahn

Joined Mar 31, 2012
26,398
Yes, it's possible to back out the circuit. But is it worth the time and effort to do so?

Do you even have the software you need to read the Gerber files?

If you are talking more than a couple dozen components, that's going to be quite a bit of time. There are tools that can make a pretty good first shot at doing this from the files, but do you have them? How much time, effort, and money are you willing to spend in this effort?

Is there any reason to believe that this outfit has given you a working design? If they haven't. what are you going to do with this schematic after you have spent all this time, effort, and money to back it out? At what point are you going to say that you are done throwing good money after bad? That's a serious question, by the way. Before you start down this road you need to decide on an amount that you are willing to spend and then be willing to walk away when that amount is reached. Otherwise you will end up sinking more and more into this hole.

It's also a good lesson moving forward: Never pay ahead to a contractor more than you are willing to lose. The best way (for both) is to set up a schedule of deliverables and assign a price to each. When they deliver what they are supposed to for one phase, they get paid for that phase. Sometimes small companies can't float the funds to quite do it this way, so one option is to pay a portion of each phase at the start of the phase and consider it to be money at risk. Another way is to make the first few phases have very short windows and terms that make payment due within a few days of completion so that even sole-person shops can reasonably risk doing the work and getting paid at the end of the phase.
 

Beau Schwabe

Joined Nov 7, 2019
80
Here are the Gerber files extracted to PNG files. What makes this difficult is the flood fill which is good practice, but visually makes it harder to decipher the connection of each layer. Personally I think this board could have been done in 2 layers. You don't happen to have a schematic at all do you?
 

Attachments

jpanhalt

Joined Jan 18, 2008
11,088
@Beau Schwabe has printed the Gerbers. So, you have the layers and the silkscreen to know which component goes where. Unfortunately, as he points out, the fills make it difficult to see connections. Had you been given the .brd files (or similar extension) form the CAD program that was used, you could delete the pours and highlight various tracks/nets to make deriving the schematic much easier.

I second the advice that this is a lesson learned. Recovery from the contractor in the US would be very difficult and expensive. Considering only the elapsed time (2 years and counting) , I would recommend either starting over or moving on to another product.
 

Thread Starter

gombault

Joined Nov 15, 2020
3
Hi All, thanks for your input and suggestions,

Yes this was a very expensive lesson. I will try and get this company to give me the schematics so I can see if someone else can fix the problems. I do have someone but he was thinking of using a pre manufacturing development board are these boards suitable for production application? You can see from the BOM file what’s required on the board and are these development boards price competitive
 
Top