4 ms·

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 registra

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.
- slededit 8y ago
  Things have changed a lot. You can get proper stainless steel stencils from lots of providers now, most PCB houses have it available as well - done to the same specs as your PCB. 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.
civilitty 8y ago
My appologies, I work largely on client/personal projects in the high speed digital/RF domain so my assumptions can be all over the place. Client budgets/deadlines leave little room for mistakes and my dexterity isn't what it once was so I use a PNP or make funky assembly jigs (my CV implementation/hands makes it easier to align with pins). 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.
- slededit 8y ago
  I've noticed it a lot going to trade shows that the North American market has turned so much to the high end that most people assume you need all this fancy gear to make anything. Its really stifling innovation in my opinion. People think they needs tens of thousands to get an MVP prototype out the door and most of the time it kills the idea. If you are a big company and already have the resources then by all means use them, but someone with a good idea shouldn't think its required to build something new. 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.

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.

slededit 8y ago
Things have changed a lot. You can get proper stainless steel stencils from lots of providers now, most PCB houses have it available as well - done to the same specs as your PCB. 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.

civilitty 8y ago

My appologies, I work largely on client/personal projects in the high speed digital/RF domain so my assumptions can be all over the place. Client budgets/deadlines leave little room for mistakes and my dexterity isn't what it once was so I use a PNP or make funky assembly jigs (my CV implementation/hands makes it easier to align with pins). 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.

slededit 8y ago
I've noticed it a lot going to trade shows that the North American market has turned so much to the high end that most people assume you need all this fancy gear to make anything. Its really stifling innovation in my opinion. People think they needs tens of thousands to get an MVP prototype out the door and most of the time it kills the idea. If you are a big company and already have the resources then by all means use them, but someone with a good idea shouldn't think its required to build something new. 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.