- Sat Feb 26, 2011 12:45 am
#121294
I seek advice on component choice (SMD vs ThroughHole) and SMD workstation selection.
I describe myself as a garage inventor (full time) – no EE background, but a voracious researcher of internet forums and textbooks and Wikipedia. Electronics comprise about 20% of my total project technology.
I now need to design and assemble my first custom PCB for a prototype. The components will be approximately 30 Power N-Mosfets (50 V, 60 Amp), with corresponding gate drivers (50% low side, 50% high side), 3 STM32s (2 64 pin, 1 144 pin LFQP), and about 10 other 8 pin components (OpAmps, voltage regulators, etc). The STM32s are obviously SMD, the gate drivers I have selected are only available as SOICs, and the other components can be either SMD or through hole.
My only experience with SMD has been at the SparkFun class at MakerFaire. I suffered greatly, but that was two years ago. I have successfully been doing strip board prototyping with through holes for the past two years.
Obviously, because of the STM32s, I am going to have to do some SMD work, much to my chagrin. And the SOIC components also force me in that direction.
Being a realist, I realize that it will probably take me about 10 iterations to perfect my project. Components cost about $100 - $150. For PCB manufacture, Advance Circuits seems to charge about $50 per pop without solder mask, and $100 per pop with solder mask. (A pop is defined as rendition of a PCB – they might ship you 3 or 4 copies of the same board, but obviously that gives you 3 or 4 bad copies). I use Advance Circuits as my example – batchPCB turnaround is too long at 3 weeks, and I just did not like expressPCB software.
All things in life come down to a time/money tradeoff. So, I will state that I value my time at $100 per hour. That is not the value of my time – that is the cost that it will take me to hire an EE to do this work if I fail.
So, finally, after the long preamble, my three questions:
1) Is solder mask required for SMD? (ie: should I buy the $50 boards, or the $100 boards)?\
2) Since I am forced to enter SMD land because of the STM32s, should I dive right in??? Should I select the majority of my components as SMD, or the minimum number of components possible as SMD?
3) I need a SMD solder station. I believe I am correct in my determination that these are referred to as “rework stations” even though it will be prototyping (that is – work, not re-work). I have googled and wikipedia’d and youTubed HotAir, Toaster Ovens, Skillets, and InfraRed. The majority of people seem to work with HotAir, with a small number in InfraRed. InfraRed used to be insanely expensive, but is coming down in price. A hot air station and pre-heater will cost $200 - $300, all in. An infrared station (Aoyue IR 710 or 720) will cost $1000 - $1300. Which is really easiest to use??? Hot Air would seem to blow parts around an be unfocused. IR does not have this problem, but you are constantly adjusting goggles.
I describe myself as a garage inventor (full time) – no EE background, but a voracious researcher of internet forums and textbooks and Wikipedia. Electronics comprise about 20% of my total project technology.
I now need to design and assemble my first custom PCB for a prototype. The components will be approximately 30 Power N-Mosfets (50 V, 60 Amp), with corresponding gate drivers (50% low side, 50% high side), 3 STM32s (2 64 pin, 1 144 pin LFQP), and about 10 other 8 pin components (OpAmps, voltage regulators, etc). The STM32s are obviously SMD, the gate drivers I have selected are only available as SOICs, and the other components can be either SMD or through hole.
My only experience with SMD has been at the SparkFun class at MakerFaire. I suffered greatly, but that was two years ago. I have successfully been doing strip board prototyping with through holes for the past two years.
Obviously, because of the STM32s, I am going to have to do some SMD work, much to my chagrin. And the SOIC components also force me in that direction.
Being a realist, I realize that it will probably take me about 10 iterations to perfect my project. Components cost about $100 - $150. For PCB manufacture, Advance Circuits seems to charge about $50 per pop without solder mask, and $100 per pop with solder mask. (A pop is defined as rendition of a PCB – they might ship you 3 or 4 copies of the same board, but obviously that gives you 3 or 4 bad copies). I use Advance Circuits as my example – batchPCB turnaround is too long at 3 weeks, and I just did not like expressPCB software.
All things in life come down to a time/money tradeoff. So, I will state that I value my time at $100 per hour. That is not the value of my time – that is the cost that it will take me to hire an EE to do this work if I fail.
So, finally, after the long preamble, my three questions:
1) Is solder mask required for SMD? (ie: should I buy the $50 boards, or the $100 boards)?\
2) Since I am forced to enter SMD land because of the STM32s, should I dive right in??? Should I select the majority of my components as SMD, or the minimum number of components possible as SMD?
3) I need a SMD solder station. I believe I am correct in my determination that these are referred to as “rework stations” even though it will be prototyping (that is – work, not re-work). I have googled and wikipedia’d and youTubed HotAir, Toaster Ovens, Skillets, and InfraRed. The majority of people seem to work with HotAir, with a small number in InfraRed. InfraRed used to be insanely expensive, but is coming down in price. A hot air station and pre-heater will cost $200 - $300, all in. An infrared station (Aoyue IR 710 or 720) will cost $1000 - $1300. Which is really easiest to use??? Hot Air would seem to blow parts around an be unfocused. IR does not have this problem, but you are constantly adjusting goggles.
