6 ms·

You don't need XRay and your reflow oven can be a toaster oven. I do recommend a cheap microscope and a good pair of tweezers though. With this you can do 0.5

You don't need XRay and your reflow oven can be a toaster oven. I do recommend a cheap microscope and a good pair of tweezers though. With this you can do 0.5mm pitch BGA although that is pushing it. I've made hundreds of prototypes this way. 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

jacquesm 8y ago
Your comment reads as if you equate 'BGA' with 'SMD', a BGA is a ball grid array with up to 1,000 tiny pads that have been pre-dipped in solder. Your toaster isn't going to work.
- extrapickles 8y ago
  You can use a toaster, but your yield will be poor. Slapping some insulation on the oven and a PID controller will improve things significantly. 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.
- slededit 8y ago
  BGA is actually easier than leaded SMD parts. The tiny leads tend to bridge easily. With BGA you can be up to half the pitch off and it will center itself. I actually only go for leadless and BGA now because anything else is more of a hassle. It is a bit rude to assume I don't know what a BGA part is.
  - jacquesm 8y ago
    The tweezers bit is what triggered that. Handling a large BGA with tweezers is going to scratch the PCB if you're not ultra careful. 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.
    - slededit 8y ago
      The tweezers are for the 0802 passives and nudging the FPGA itself. It takes forever but then so does programming the pick and place for a one-off. 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.
- hak8or 8y ago
  Yes, it will. Sure, it won't do wonders with 0.5mm pitch bga's, but 217 pin 0.8mm ones are doable even with a cheap Chinese hot air station. That's how I did these boards. https://brainyv2.hak8or.com/ https://brainyv2.hak8or.com/
- lightedman 8y ago
  "Your comment reads as if you equate 'BGA' with 'SMD'" BGAs are SMD (Surface-Mount Devices) for all intents and purposes. And I've fixed plenty of BGA-mounted GPUs with a Black and Decker 1200W heat gun.
jimmyswimmy 8y ago
Agreed, if you meant a toaster oven. It does take precise temperature control if you want any chance at reliability. And a fine touch. It's easy to line the whole thing up one row off and have to scrap the part, which is a bummer if you can't re ball it.
- mips_avatar 8y ago
  If i have never reflowed a pcb before, how should i learn?
  - st26 8y ago
    Reflow trash PCB's. Focus on packages like TQFP, and discrete components of human-visible sizes.
civilitty 8y ago
With this you can do 0.5mm pitch BGA although that is pushing it. 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.
- slededit 8y ago
  I use a 10x jewelers microscope and tweezers to get the alignment perfect. The hardest part is actually applying the solder paste there is no room for registration errors. I triple check everything. 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.
  - stewartbutler 8y ago
    If you have access to a laser cutter you can make a pretty decent solder stencil by folding some clear package tape (so all adhesive is on the inside) and having it cut out the hole pattern. Lay it down on the PCB, squeegee some solder paste over it like you would a real solder mask, and carefully peel the tape up. 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.
mips_avatar 8y ago
Someone told me a spartan 6 might be enough for what I need, will qfp make my life easier?
- slededit 8y ago
  I personally find them more annoying than just BGA. But conventional wisdom is they are easier since technically you can solder them with a soldering iron and eventually you'll get lucky and remove the last solder bridge without creating a new one. 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.
- st26 8y ago
  IMO start with QFP, yes. It's not trivial and has a lot of hand work, but critically you can both see & fix your mistakes.

jacquesm 8y ago

Your comment reads as if you equate 'BGA' with 'SMD', a BGA is a ball grid array with up to 1,000 tiny pads that have been pre-dipped in solder. Your toaster isn't going to work.

extrapickles 8y ago
You can use a toaster, but your yield will be poor. Slapping some insulation on the oven and a PID controller will improve things significantly. 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.
slededit 8y ago
BGA is actually easier than leaded SMD parts. The tiny leads tend to bridge easily. With BGA you can be up to half the pitch off and it will center itself. I actually only go for leadless and BGA now because anything else is more of a hassle. It is a bit rude to assume I don't know what a BGA part is.
- jacquesm 8y ago
  The tweezers bit is what triggered that. Handling a large BGA with tweezers is going to scratch the PCB if you're not ultra careful. 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.
  - slededit 8y ago
    The tweezers are for the 0802 passives and nudging the FPGA itself. It takes forever but then so does programming the pick and place for a one-off. 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.
hak8or 8y ago
Yes, it will. Sure, it won't do wonders with 0.5mm pitch bga's, but 217 pin 0.8mm ones are doable even with a cheap Chinese hot air station. That's how I did these boards. https://brainyv2.hak8or.com/ https://brainyv2.hak8or.com/
lightedman 8y ago
"Your comment reads as if you equate 'BGA' with 'SMD'" BGAs are SMD (Surface-Mount Devices) for all intents and purposes. And I've fixed plenty of BGA-mounted GPUs with a Black and Decker 1200W heat gun.

jimmyswimmy 8y ago

Agreed, if you meant a toaster oven. It does take precise temperature control if you want any chance at reliability. And a fine touch. It's easy to line the whole thing up one row off and have to scrap the part, which is a bummer if you can't re ball it.

mips_avatar 8y ago
If i have never reflowed a pcb before, how should i learn?
- st26 8y ago
  Reflow trash PCB's. Focus on packages like TQFP, and discrete components of human-visible sizes.

civilitty 8y ago

With this you can do 0.5mm pitch BGA although that is pushing it. 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.

slededit 8y ago
I use a 10x jewelers microscope and tweezers to get the alignment perfect. The hardest part is actually applying the solder paste there is no room for registration errors. I triple check everything. 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.
- stewartbutler 8y ago
  If you have access to a laser cutter you can make a pretty decent solder stencil by folding some clear package tape (so all adhesive is on the inside) and having it cut out the hole pattern. Lay it down on the PCB, squeegee some solder paste over it like you would a real solder mask, and carefully peel the tape up. 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.

mips_avatar 8y ago

Someone told me a spartan 6 might be enough for what I need, will qfp make my life easier?

slededit 8y ago
I personally find them more annoying than just BGA. But conventional wisdom is they are easier since technically you can solder them with a soldering iron and eventually you'll get lucky and remove the last solder bridge without creating a new one. 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.
st26 8y ago
IMO start with QFP, yes. It's not trivial and has a lot of hand work, but critically you can both see & fix your mistakes.