G30 prototype

You using a soldering iron or stencil and oven / hot air?

Well I am using a stencil, then reflowing it on that Voltera thing I bought. But the boards donā€™t have solder mask between pins and I only had 1 of 4 boards not bridge on me, or shift position while reflowing.

I tried pre-tinning the pads then using my hot air rework gun but even on low air setting, kept shifting.

So Iā€™m hand soldering.

I pre-tin the pads w/ low temp solder and lots of flux, getting them as even as I can.

Then I position the chip, painstakingly, as it wants to roll off the low solder beads with the slightest bit of pressure.

I lay some flux just past the pin edges in a bead, and try to get one corner to mate without disturbing the chip. (If that fails I get a little more forceful and hold the chip in position with my hand while pushing down slightly on the tip of the pin.)

Then I check to make sure everything lines up as I do the other corner.

After that I push the solder iron through the flux beads I laid down just outside of the pins, and touch the pins a few at a time, until I see the pins wet and flow, going down the line.

Then I check for any bridging (usually isnā€™t any this way), and then check for hard short on vcc.

If thereā€™s no short I power it up.

ON a couple of them Iā€™ve had pins not quite make contact using that method so I have to go back around pushing down on the pin edges with the iron. That causes the solder to bridge sometimes so I come back through with wick and flux and suck out excess.

Once in a while I have a stubborn pin (tinned pad lower than the rest) that I have to push down while soldering and hold until it cools, then inspect to see if itā€™s bridged. Amazing that a micron sized gap can stop the show cold.

Anyway, it works. Time consuming until I get boards with mask between the pads, or a better reflow system than the voltera. But, itā€™s working.

I say itā€™s working but if you look at that last board i posted, youā€™ll see I had the two G30 processors (one burned, one good) on and off so many times that I wore the solder mask off the traces around the CPU, with friction from the wick. :slight_smile:

That board must have had the G30 mounted 8 or 9 times before I found the solder bridge under one of the caps.

Short only showed up when the processor was mounted, but that was due to the stupid way Iā€™d set up my ground plane. It turned out not to be the MCU at all (even though it only showed up with it mounted.)

Which is why the G30 I powered up in that state turned in to a miniature toaster oven, I think. :slight_smile:

Next time I order 5 boards Iā€™m ordering 6 processors. :slight_smile:

Canā€™t wait until I get to the castellated G120 and 400ā€™s. Those will seem like a piece of cake compared to the G30.

1 Like

Meanwhile the larger, more pins-es-es G80 is pretty damn intimidating. Probably a good thing itā€™s not in stock. It lets me skip ahead to the G120 SoM. :slight_smile:

One day I will do a vid of the tricks I have learntā€¦

QFNā€™s, 0603 are easy and even 0402ā€™s are not overly challenging with the correct techniques.

How far you live from IL? Iā€™m not against paying for qualified instruction. :slight_smile:

3 Likes

Holy crap thatā€™d be one heck of a mileage bill. :slight_smile:

3 Likes

Your ok as in the 3rd world we use KMā€™s so mileage is not a problem :joy:

1 Like

Hahah!

New Zealand is where my son is taking his honeymoon next May. Iā€™m part envious of the journey heā€™ll be on, and part grateful I donā€™t have to sit on a plane for 24 hours like he and his soon-to-be-bride will have to endure!

meh, only 12hrs from LA :slight_smile:

He and the wife to be should have an awesome time, if they need some ideas on places to go let me know. But in saying that i assume they have done a heap of researchā€¦

1 Like

Heā€™s like me. Over-researches everything at the expense of getting things done. :slight_smile:

3 Likes

Not thatā€™s Iā€™ve done it or I am otherwise good at SMT but here are some tips Iā€™ve learnt over the years.

Soldermask repels solder, you need it around ever pin. I think you figured that part out. When soldering SMT use solder paste vs filament. For soldering smt ics use the drag method. When soldering thermal vias, heat the chip from the bottom not the top. If you need to remove an ic easily use chip quick.

SMT usage is easy with solder paste, 2 or 4 layer PCBs, PCB stencils and a cheap IR oven ($360 US). Iā€™ve been building with these tools using 0402 components with ease. Desoldering with a hot air gun ($50 US). Chip quik for resoldering using the hot air gun.

Iā€™m not going to beat myself up too hard, yet. Iā€™m just getting started at this and have assembled all of 4 real PCBā€™s in my entire life at this point. And (eventually) all four worked. :slight_smile:

The next couple I do will be much easier. A backplane, for plugging in modular boards (sensors, relay controllers, whatever) which is just through hole slots, CPU boards w/ card edge connectorsā€¦ and then the first couple sensor and control modules I plan on building.

Eventually Iā€™ll have to figure out how to design an enclosure for all of it.

Has to be generic enough of a design to tackle three different projects, HVAC pneumatic to digital conversion, a security system, and then another HVAC project when I take my little mini excavator and dig up about 1500 feet of ground 12ā€™ deep to lay loops. Going to use the G120 or G400 to control the circulation pumps, read manifold and loop temps, etc.

So thereā€™ll be some interesting learning there, on how to read thermistors which are buried under the ground 12 feet, 300 meters away from the controller. And it has to be bulletproof because re-running them will involve lots and lots of digging.

First mini-step is a replacement for this timer which keeps getting out of whack. It controls a couple of relays that then control pneumatic comparison valves for AC on/off and our outdoor air mix.

Then thermistors in the rooms and I change over the pneumatic relays here;

And of course replace the zoned pneumatic thermostat feeds here;

Hopefully I can decipher enough to get the board to turn on the AC when the time and room sensors call for itā€¦

Then next year I go digging up this yardā€¦

With the mini excavator I ownā€¦

(hereā€™s a point of view shot)

And one my wife took

Anyway, I figure Iā€™ll build my own geothermal system at that place, with horizontal loops, all set up to be run off a GHI / .NET board.

So a modular system is needed so I have one platform to do security systems, RFID entry and inventory systems, pneumatic to digital conversions, geothermal installations, etc.

Pretty decent money to be made around here, especially on the geothermal stuff, lots of farmers with big yards that have plenty of room for horizontal loops, and this area sits on top of a big aquifer with water tables very close to the surface so they should be stupid efficient. Cheaper than drilling wells to drop the loops in, by a large factor, and if I can make the system highly efficient and programmableā€¦ so much the better.

2 Likes

Well Iā€™m neck deep in it now.

I donā€™t think I could have sucessfully made this in two layers @Dave_McLaughlin!

By the time I got to the end, even with two signal layers, I had to ā€˜borrowā€™ the VCC layer for a couple of traces. The ground plane is fully intact, though.

Gotta design the backplane, and start working on the modules I need.

ETA: I managed to route all of the high speed signals away from the oscillators this time. :slight_smile:

3 Likes

Addiction complete :joy:

Haha yeah once I sit down to start I canā€™t seem to stop. I started this board ~9pm wednesday. Got a few hours of sleep this afternoon, but put 24.5 hours in to the dang thing. A lot of that was designing devices in Eagle.

Well, plus that one time I got stuck and did ripup !; and started clean. Nothing more depressing than getting 95% routed and going ā€œoh crap.ā€

The only reassuring thing is on ā€œtake 2ā€ itā€™s inevitably much cleaner.

The joy I feel at destroying the last airwire is palpable!

Now on to more modules. I have a lot of crap to build. :slight_smile:

1 Like

Are you going to pour copper between all those empty spaces and connect them to the ground plane on the bottom and VCC on the top?

Do I need to? Thereā€™s no signals to shield. The only pour I was planning was around the VRMā€™s to give them a little more heat sinking. (Although donā€™t need much, if any, there, makes me feel better)

VCC is just traces, no pour.

Ground plane is solid, not a single break except where vias poke through.

Any signal return should be able to find return path very easily.

ETA: I have thought about carving out the oscillators and single point connecting them, and likewise separating ground on each VRM and doing the same.

Will defer to anyone who knows a lot more than I do about EMI, though! I donā€™t know much!