Raspberry Pi B+ header board for smart home automation

"This is the manufacturered PCB top side:" _____________manufactured_________________ and I'm pretty sure the second one should say "This is the manufactured PCB bottom side:"

:-)

Nice to see this sort of thing being done, but I would comment on the PCB.

It seems you used Design Spark's auto-router. None of these are brilliant and this one is somewhat less brilliant than others.

For a board of this size there are a *lot* of vias, and the PCB manufacturers charge extra for these. They are also a potential point of failure. With only a cursory glance I can see many that can be removed simply by swapping track layers.

There are also entirely right-angle bends. There is a risk of these being acid traps in the production process, resulting in thin track right on the angle (admittedly less of a problem with modern processing). Unless you are *very* tight for space it is usually practical to make these pairs of 45deg angles.

There are (what look like) three rather strange pads that look like they are through ones. Two of them look as if they are just touching the edges of tracks on the opposite side. Your silk colour is the same as your pad colour so I suppose these could just be orientation marks, although that seems unlikely.

Finally, quite a lot of the routing goes between pads unnecessarily, this increases the chance of bridging, especially when inexperienced people are doing the soldering! Even though there is solder resist, the tiny bump of the track can have a sort of wicking effect.

Sorry if this all sounds negative. I like what you've done generally, but have had very many years of servicing professionally manufactured PCBs that are - shall we say - less than perfect.

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W J G

Few boards this size and few layers benfit from Autoroute, as to set up autoroute properly and grouping signals, powers etc with min layer changes, min/max width track, min/max connection width to via/pad/smd, etc. etc. takes longer than just manually routing it.

The last time I saw a PCB manufacturer charge on number of vias was nearly 20 years ago. Few these days will start charging extra for blind vias and and minimum less than 0.2mm or 0.15mm depending on your manufacturer. Then that is a charge for smaller size drill to use not number of vias.

They are also more of an issue for EMI/RFI as right angles create various sub-antenna wavelengths in tracks with right angles more than 45 degree bends.

Looking at the photos of PCBs they look like poor choice of ident layer (silk) for pin 1 idents of connectors where a Number '1' being used would be better or creating a symbol with a square pad for pin 1.

You must use some weird processes then as that sort of track between pads is very common and they are under the solder resist. This sort of practice has been done for over 30 years to my knowledge adn for the size of tracks used is quite safe. That would pass design rules and all manufacturing stages for all processes I have seen for many years.

Having had to do worse than that on a 150 way connecter on 2 sided PCB and the connector had 5 rows of 2mm spaced through hole pins.

About 35 years ago people used to boast about how their CAD could get

3 or 4 tracks between through hole pads on DIL packages. Fact it could not be easily manufactured at the time did not matter.

but have

Well lets see many years and PCBs from 1 to 8 layers from 10mm x 10mm to very large .... Oh and military/aviation grade PCBs, highest temp range so far PCB and components withstand 195 deg C as testing process for

7 days continuous and also temperature cycled.

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Paul Carpenter          | paul@pcserviceselectronics.co.uk 
    PC Services 
  Raspberry Pi Add-ons 
 Timing Diagram Font 
 For those web sites you hate

Yup - seen it tried - however that was some 25 years ago when pin-counts on chips really started to increase - the place we used did seem to manage 2 tracks between 0.1" pads relatively successfully... (I wasn't doing the layout for it)

I've seen worse PCBs developed for Pi applications - however there is a positive in that at least the OP is devleoping something useful. Always a good thing.

My own PCB experience started some 20-30 years ago with etch resist pens, then letraset and photocopying designs onto acetate for photo-resist boards, complete with noxious chemichals, etc. I designed several 6502 based boards and interface cards for a project I was doing at the time, then nothing for many years, but a few years ago I decided to see how the "industry" had changed and was plesantly surprised to see that for the hobbyist it's really easy now to get started (almost too easy?) - although prices are high for one-off's (they always were), but for the serious hobbyist, I think that having your own PCB professionally made with your own layout for under £100 is worthwhile.

Gordon

The design of the PCB is not my focus. What it does is what I'm interested in and how I can use it. At the end of the day I picked up a free tool and out-sourced the board manufacture to Ragworm as a one-off. I don't intend to put this into production in large numbers. It's a prototype that may get built in 10's at the most.

It works and does the intended job. I can now focus on the innovative applications and services that it enables :-)

If someone wants to pick up my design and improve it and then turn it into a competitively priced product for general sale, I'm happy for this to happen.

Thanks

Rob

I've used these folks:

For prototyping. I can fit 6 Pi sized boards into their smallest panel. Not cheap at under £100 per panel for I think its acceptible for prototyping and personal use.

However I've just checked ragworms prices - might be cheaper for quick prototyping of e.g. 6 boards. I'm not sure they were when I last did some boards...

Gordon

....

to

Totally agreed, the board could be better, better than quite a few from commercial places.

Mine started with letraset, red/blue and other type tapes yes hand layouts on 2:1 scale, with draftsmen to do it. Back in late 70's. First micros 8085 and various 16 bit etc from DIl to newer packages at moment avoiding BGA where possible.

Well various phases of manual and CAD layouts with layout folks or me over the years. Probably done more boards in the last 5 years including a dozen for Pi appilcations.

So many places can take board files and produce them Beta layout, multi- cb, pcb-panel and others competitively priced even for small quamtities. Mind you waiting for customer to come back for small production run of

100 boards at moment.

Last small run was 2 off of 2 boards that was 100 pounds all in and free stencil for SMD

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Paul Carpenter          | paul@pcserviceselectronics.co.uk 
    PC Services 
  Raspberry Pi Add-ons 
 Timing Diagram Font 
 For those web sites you hate

Have you guys never heard of ? They do "community" PCB manufacture at $5 per square inch. This board would cost $52.47 for the minimum of three. Hard to beat that with a stick. They even do runs every day with a turn of 12 days on 2 layer boards.

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Rick

No, but I'm in the UK, so I pay in £ not $.

Gordon

Uh, the credit card company will convert that for you... I don't get your point.

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Rick

Similarly, pcb-pool.com would do four of those boards for their minimum

It wouldn't be unusual for USA->UK shipping charges to be only slightly lower than the item itself at those sort of prices.

Then there's the postage and the tedious customs duty/palaver! And that's before considering export licences (US: licenses ?). Electronics=weapons to the US government!

If it wasn't for all that we UKers could make a killing on some US prices! Have our petrol (US: gas) shipped over, for instance!

Perhaps sigs for this group should have a mandatory world location indicator. Oh, look - mine does already!

John

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John Williams, now back in the UK - no attachments to these addresses! 
Non-RISC OS posters change user to johnrwilliams or put 'risc' in subject! 
Who is John Williams? http://petit.four.free.fr/picindex/author/

I took a look at pcb-pool and I got a quote for ?107.45 net, ?132.17 gross, not sure what the difference is, VAT maybe? I selected conservative options, soldermask - yes, silkscreen - top only. Surface finish didn't seem to affect the price.

How did you get your numbers? If shipping is ?50 something is wrong!

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Rick

I think you like to create problems. I get electronics from overseas all the time. No hassle and *very* cheap. I know for a fact the US government doesn't consider your Arduino type toys to be export controlled. I'm in the business.

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Rick

My price did include VAT, but I didn't get as far as adding it to the trolley, so probably not shipping.

Really it's not uncommon to see that level of shipping "over here" for various USA sellers, e.g. a Buy It Now item on eBay I've been looking out for, that are like hens' teeth over here ...

Glad to hear it's not considered "normal" over there.

Sorry just realised the price you see will likely be different from that shown to me ...

I'm British. I live in Britian. I buy British and support the local economy when I can.

Gordon

I was able to improve it to ?82.04 net, ?100.91 gross. Seems they distinguish between "Gerber" and "Extended Gerber" formats. Still, that's a factor of 2 from your number. How did you get that price?

It's nice that they offer assembly as well. I haven't shopped prices on assembly in a while. I don't have a feel if their assembly price is competitive.

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Rick

There is nothing to control eBay prices for shipping. They may or may

*not* reflect the cost of shipping. Often vendors (in general) charge "shipping and handling" which is intended to cover the cost of packing the order. On eBay it is not uncommon to include profit in the shipping number so that if you return the item they still keep the "shipping".

I just checked pcb pool and they only want $10 to ship a board order to the US by mail or $25 by courier which I assume means FedEx or something similar.

I'm not a fan of their web site. I had been giving me prices in ?. Now that I registered with a UK address it is giving me prices in $. Go figure! But if I can reach a point where I can use the web pages with confidence, I will consider them for my next order. BTW, the prices are now all showing in $. I just need to figure out what NET vs. Gross is. Now that it is in $, the two are the same so I'm betting it is VAT.

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Rick