Prototyping (hints collection): PCBs for SMD, PCB layout, PCB DIY /manufacturing

[asilva10]

Hi All,
I'd like to collect in this thread your hints for prototyping in general with topics such as:

1) PCBs for SMD: there a many parts that use QFN, DFN, SOT, ... packages and it is very hard to buy one generic prototyping board with some of these pads.
2) PCB layout: what is the simplest software to use assuming at maximum 2 layers?
3) Preparing the PCB by yourself: step-by-step for different methods, where to buy the cheapest items (PCB, chemicals, etc.)
4) PCB manufacturing: how to obtain an up-to-date list of the cheapest PCB fabs? For 1, 2, or 3 boards?

Thanks

[Jon Chandler]

PCB Fabrication Sources is a summary of sources I had used or that I'm familiar with.  It's reasonably up-to-date with recent information in the comments section.

[Rory]

Never reinvent the wheel if it's cheaper to buy off the shelf. This is one of the reasons why Arduino is so popular.

If you are building for yourself on a limited budget, make your PCB designs general purpose and make plenty of extras with future projects in mind. Tooling costs make up the majority of the price of board orders.  We include grids of plated through holes on prototype boards whenever we can, gives us space to add functionality we may have left out but later found we needed.  Near the grids run power supply and ground rails for additional circuits. Most board vendors we use charge a fixed rate for drilling up to a certain hole density. So if you have room to cram in a grid sufficient for a couple of DIP14's or extra SO- type footprints with breakout pads, let the vendor give them to you for free.

On your prototype boards make your plated through holes for through hole components larger than what the component data sheet calls for in the footprint. More clearance between lead and plating means less chance of damaging the pad or through-hole plating when desoldering.

Include pads for test points, whether you populate them with terminals or not. Include a test point for clocks, grounds and power supply rails as well as all the signals of interest. It is tough to troubleshoot a 64 pin QFP when you have to probe the pins directly. We use a package footprint that includes breakout vias for each of the pins and route to the vias from the rest of the board. Then you can probe the vias when troubleshooting instead of taking a chance of shorting pins on the narrow pitch device.

[sleemanj]

Hi All,
I'd like to collect in this thread your hints for prototyping in general with topics such as:

1) PCBs for SMD: there a many parts that use QFN, DFN, SOT, ... packages and it is very hard to buy one generic prototyping board with some of these pads.
2) PCB layout: what is the simplest software to use assuming at maximum 2 layers?
3) Preparing the PCB by yourself: step-by-step for different methods, where to buy the cheapest items (PCB, chemicals, etc.)
4) PCB manufacturing: how to obtain an up-to-date list of the cheapest PCB fabs? For 1, 2, or 3 boards?

Thanks

1: https://www.eevblog.com/forum/oshw/universal-smd-board-design/?topicseen
2: Fritzing (you said simplest, I challenge anybody to find one that is simpler)
3: Dry Film Photoresist or Toner Transfer, or pre-sensitised positive photoresist, or spray on positive photoresist, or paint/spin coat negative resist, Google is your friend.  See the Homebrew PCB's Yahoo Group
4: Cheap proto houses off the top of my head, iTead, Seeed Studio, OSHPark, Smart-Prototyping, Elecrow