A review with screenshots : https://www.javaworld.com/article/2076574/developer-tools-id...
If you have the budget for professional assembly, then I would start with a Digilent product that has an available reference design you can copy later. First get used to the FPGA and how it works (they are largely incomparable to a CPU or GPU except for the fact that they both have transistors). Then, design a simpler board with a smaller FPGA and work your way up to the big 500-1k pin chips.
The fear of BGA parts is seriously overblown. The only real expensive part is the finer pitch parts will require tighter tolerances on the PCB which will take you out of the PCB batch services price tier.
edit: toaster oven, not toaster
If you screw up the solder job, you can use a hot air gun to remove the BGA part, reball it (using a stencil, fairly cheap if its a common package), then try reflowing again.
If you practice for a few hours on scrap electronics, you can get good enough at it.
It is a bit rude to assume I don't know what a BGA part is.
Anyway, if you do this stuff often enough then I see no reason why you wouldn't get the proper tools, a rework station and an actual reflow oven or something with a PID controlled heating element would make your life so much easier. Working with bad tools would drive me nuts.
The reason the larger BGA center themselves is as soon as the solder goes fluid there is a lot of accumulated surface tension trying to reduce the size of the bridge and that will center the part all by itself. For that to work properly though everything has to become fluid more or less at once and stay fluid until the part has shifted to the right position.
As for the reflow you can actually get more consistent results with the toaster oven - It just won't be able to handle the volume of actual production. Whatever you do just don't try going "semi-pro" and getting one of those IR ovens from China. Stick with the $40 walmart special. The toaster oven when heated slowly is much less likely to have hot and cold spots. Stenciling and placing parts take up a lot more time and are much more error prone.
If you have actually figured out how to consistently make boards with BGA-256/512 0.5mm pitch parts with just a toaster, I'd love to learn more about your technique. Even with professional inspection equipment and a pick and place, it's rarely worth the effort unless I have an imminent deadline.
For a beginner, I doubt the cost of trial and error would be cheaper than just having someone else do it. He could go with a larger pitch [edit: and smaller pin count] but I have never successfully introduced someone to FPGAs without a relatively huge chip capable of running a soft core closer to what they're used to with in general purpose computing.
As for the reflow profile I raise the temperature gradually, with the thermocouple taped directly to the PCB with kapton tape. I do this manually, not with an automatic controller. My toaster oven is a convection model with a fan which helps, and I had some trial and error with the rack position.
The part in question is: TPS62180 which is a dual phase step down converter.
Edit: I think you are conflating I've done both high ball count and 0.5mm. Never both at the same time. I've soldered high ball count Xilinx FPGAs at 0.8mm which was relatively easy. Also I stress these are for prototypes. You can do production runs and that is how the company behind 3DRobotics got their start in the early days of quadrotors but its a whole other ball of wax.
Been a few years, but IIRC a labmate of mine got a few units of .5mm highish ball count to work using that process and a toaster oven, but it is a bitch to test.
Would maybe do for a hobby project assuming you have access the equipment (e.g. a hackerspace or something) and are willing to drop a buttload of time into trying to get it to work, but if you are working for someone it is probably more cost effective to save the manhours and get it done by someone with the right equipment.
The only time it really fails is if I'm lazy applying the solder paste or if I stop paying attention during reflow. Doing it in house saves a ton of money which is really important when you are trying to get your first prototypes up and running. Plus it also keeps you deeply in tune with what is possible to manufacture and what isn't. DFM stops being just a checklist.
We'd have a lot more hardware startups if people realized how cheap and easy its become. You need the prototype to get funding.
If you can, I'd really recommend talking to dentists who are retiring in your area or buying an XRay machine on ebay. They're pretty cheap and relatively safe and will open up a whole world of PCB fab. The problem with BGAs is the lack of feedback: if you have a chip with hundreds of pins and precise requirements for power boot up timing or dozens of impedance matched traces, figuring out what went wrong with your boards is literally impossible without proper inspection.
Since you have an intuitive feel for soldering BGAs already, I think that with a visualization of the solder joints you would be able to solder high pin count chips at small pitches. Most issues that I've experienced with complex BGAs are caused by mass manufacturing where you dont have the room to reflow every 10th board and you find out too late that a variable (from personal experience: el nino) has changed and reduced your yields by double digits. If you can take the time to do it right by hand, the sky's the limit.
If your back is against the wall you can also hotfix design mistakes like swapping two LVDS MIPI2 pins by using a laser drill to strip the plating on microvias at an angle to preserve the trace above it and resoldering them with wire only slightly bigger than IC interconnects. An almost completely useless skill but nothing beats the feeling you get when you can command RoHS compliant surface tension to do your bidding. Fair warning though: here be dragons.
On the high speed digital front we do have 1Ghz DDR3 and its worked very well - we don't even use controlled impedance. Of course we are extremely careful to keep traces short and length matched. Our application can handle a very small error rate, however in practice we haven't seen any corruption at all in testing.
Its not the right approach if you are pushing the envelope of technology. But if you need a bit more grunt than an atmega by all means design in the ARM SoC and DDR3. You don't need fancy gear to do it.
Edit: Also thanks, we're looking into expanding more manufacturing in house and you've given me some ideas. I'll definitely look into an XRay machine.
It seemed like it wasn't I need fancy gear to make blinky lights, but rather for anything better than 8-bit, kilobyte, and low MHz, the only parts available was the fancy commercial stuff.
I do occasionally do small (100+ pins) BGAs - for that I get a steel solder stencil made and use solder paste and a cheap Chinese reflow oven
Once you see how easy it is to reflow a board you won't want to bother with hand soldering DIP packages anyway.
On the other hand, I designed a STM32F4 based design last year and it was glorious. SnapEda for all symbols/footprints, Altium design vault for a specialized FPGA design, and github for a STM32 reference design PCB file using the same layers/copper weights as my requirements with imported fab design rules for good measure. The PCBs cost like $1500 and assembly was only $1600. 10 years ago I used to pay that much per single board in quantities of 30, for roughly the same complexity. This time, the whole thing (minus firmware) took a weekend.
Good luck with your mfg! If you have a chance, please blog about your experiences. There arent enough people spreading the art of solder.
The trick with BGA parts is to use solder paste and a stencil. Once you try it you will never go back. By the way make sure you read the xilinx documents extremely carefully. Its easy to forget to wire PUDC_B and prevent the thing from ever being programmed. There are lots of little gotchas.
With LVDS, make sure to keep tracks short,have some impedance control (doesn't need to be super strict), and match trace lengths. One issue I had before was a clock (90Mhz I think) that wasn't quite in sync. Ended up ordering a new board with a 8 channel inverter, and snaking the clock through a few of the the gates to get a slight delay.
Have you ever considered a DIY youtube channel?
If you, @slededit, others on this thread did something like Louis Rossmann, that'd be fantastic. I've never even seen a dentist's x-ray machine, much less seen it used for DIY design. That'd be amazing to watch.
Louis Rossmann https://www.youtube.com/channel/UCl2mFZoRqjw_ELax4Yisf6w
(But maybe y'all would dial down the rhetoric from an 11 to a 8 or 9.)