Author Topic: AB18x5 Breakout Board  (Read 4319 times)

ChemE

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Re: AB18x5 Breakout Board
« Reply #15 on: January 23, 2017, 10:52:52 PM »
Very curious to see if it functions.

WhiteHare

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Re: AB18x5 Breakout Board
« Reply #16 on: January 24, 2017, 05:14:17 AM »
The I2C version (AB1805) might be slightly easier to solder because it does not rely on the bottom pad for an electrical connection, as the SPI version does.  That's because on AB1805, the thermal pad appears to be redundant with pin 9 (both being labelled a VSS pin).  On the SPI version (which is the one shown in the photo), if that thermal pad connection is not electrically sound, then it's a complete re-do, as I see no way to remediate it short of complete removal and starting over.  Fortunately, the same board would work for either chip, except that the silkscreen on the bottom would be wrong.  That's partly why I left the pin numbers on the top silkscreen.

Anyhow, I'd say this chip is much harder to solder than the BQ25504 chip of the same size.  That's because the pin connections on the BQ25504 go up the sides of the chip a bit more, and so it's easier to see if each soldered connection is a good one.  On the AB1815, it's just very hard to see.  If I had a photo of what a properly soldered AB1815 looks like, it might be easier to judge.

« Last Edit: January 24, 2017, 05:27:25 AM by WhiteHare »

WhiteHare

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Re: AB18x5 Breakout Board
« Reply #17 on: January 24, 2017, 08:32:58 AM »
Very curious to see if it functions.

Me too!  I'm supposing that if I can read and write to the Seconds register (0x01), then that's a good enough test, at least for now.

WhiteHare

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Re: AB18x5 Breakout Board
« Reply #18 on: January 24, 2017, 12:47:00 PM »
Just now looking at the rfm69 chip to see how it was soldered onto the HopeRF module, and it's in the same league: just looking at it, I don't see a way to tell whether it was adequately soldered or not.  I know that it was correctly soldered, though, because it functions correctly.  Maybe the *only* way to tell is by using the chips and seeing if they work as expected.

I think this chip may be just too difficult for me.  I'm going to shelf it and maybe revisit it at a later date.
« Last Edit: January 24, 2017, 12:50:05 PM by WhiteHare »

WhiteHare

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Re: AB18x5 Breakout Board
« Reply #19 on: January 24, 2017, 03:04:49 PM »
In case some future reader of this project has interest in a breakout board for the AB1805 (I2C), instead of the AB1815 (SPI), attached are files for the same board, but with bottom silkscreen labels appropriate for the AB1805.

ChemE

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Re: AB18x5 Breakout Board
« Reply #20 on: January 24, 2017, 05:52:58 PM »
I'm not even sure how you would go about soldering the ground pad with a hand-held iron.  Bummer that you've hit a snag.  If I do get a working reflow oven knocked together I can send your board through if you'd like.  That project isn't on the immediate horizon but I plan on doing it this year. 

WhiteHare

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Re: AB18x5 Breakout Board
« Reply #21 on: January 24, 2017, 06:35:33 PM »
Actually, I am using a reflow/toaster oven for this project.  I only recently made the switch. 

The lone AB1815 SPI library on github doesn't come with an example script.  However, both of the I2C AB1805 github libraries for the AB1805 do come with example scripts.

So... I soldered an AB1805 onto one of the boards, ran the dantudose I2c example script, and voila, it produced the expected output:

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Although one could do more extensive tests, I think that's pretty solid initial validation that the PCB Breakout board works. 

Project complete.   :)

perky

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Re: AB18x5 Breakout Board
« Reply #22 on: January 24, 2017, 06:50:02 PM »
Get yourself an adjustable heat gun, like this (UK only unfortunately):
https://www.machinemart.co.uk/p/evolution-hdg200-2000w-heat-gun/

If you get one make sure it has continually variable temperature, and continually variable speed down to a very low level. There are many with variable temperature (50degC - 650degC are common), but not so many with variable speed, they tend to come in either two or three speed settings, you'll need one that's very low speed for soldering delicate components. Oh and a reducing nozzle but they usually come with the gun.

This is probably the most useful tool I have in my toolkit, I can solder just about anything with this within reason ;)

Mark
« Last Edit: January 24, 2017, 06:53:37 PM by perky »

TomWS

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Re: AB18x5 Breakout Board
« Reply #23 on: January 24, 2017, 09:33:18 PM »
This https://www.amazon.com/gp/product/B00ITMPQS2 works well if you want to unsolder a chip.  Resoldering is another story - the forced air will blow most components off their pads. Use this to remove a device's defective solder operation, fix the pads, etc, paint new paste, toaster oven reflow to repair.

Uh, you probably only get two retries before you've broken something... depending on how good your toaster heat profile is and whether your device is MSL3 and it's 'pink'...

Tom

perky

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Re: AB18x5 Breakout Board
« Reply #24 on: January 25, 2017, 06:31:05 AM »
There are ways around the air flow blowing components off pads, for example using a piece of gauze with different grid sizes can control it reasonably well. The hot air rework stations can go quite low in air flow but I've found they're considerably more expensive than heat guns.

WhiteHare

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Re: AB18x5 Breakout Board
« Reply #25 on: January 25, 2017, 07:10:55 AM »
I later discovered that some of my initial "floating away" problems were probably just me being too eager to remove the pcb from the oven.  The sliding metal tray that the pcb sits on tips down at an angle if I pull it out too far, and that caused some dislocation because everything was still molten.  Now I open the oven door and wait two minutes before moving anything.  Mea Culpa, and obvious in retrospect, so just a warning for other reflow oven beginners like me who might try this.
« Last Edit: January 25, 2017, 07:21:13 AM by WhiteHare »

TomWS

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Re: AB18x5 Breakout Board
« Reply #26 on: January 25, 2017, 08:55:16 AM »
Now I open the oven door and wait two minutes before moving anything.
It takes my oven about 5 minutes to cool down to a touchable temperature after opening the door.  I use that time to start a cup of coffee.

Tom

WhiteHare

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Re: AB18x5 Breakout Board
« Reply #27 on: January 25, 2017, 01:27:36 PM »
The step that, at least for me, stands out as by far the most difficult in the entire process is the initial chip placement.  By that I mean the chip has to be set reasonably close to the ideal even if surface tension helps fine tune it during the reflow.  I'm  not yet sure just how close "reasonably close" needs to be, but... pretty close.   

I have fairly steady hands (probably better than average), and nonetheless my first placement would often not be close enough (based on my guessing of what was close enough).  So, I would then nudge it with a pair of tweezers until it finally ended up where I thought was "reasonably close".  However, it's very easy to either overshoot or undershoot or accidentally rotate it, all of which leads to more nudging.  Now, granted, eventually it gets to where it needs to be, but it can be frustrating at times.  Any of this sound familiar?

So, if there are any tips on that part of the process , I'd be interested to hear.  In comparison, the rest of it is relatively straight forward.  I'm starting to think that making some kind of simple but small x-y table with a fixed vacuum chip holder above it that simply plunges in the z-axis might be the way to go.  That way one could literally dial in the chip placement and remove imperfect hand motions from the equation.  Yet, I haven't read of others doing that, so there must be easier ways.

WhiteHare

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Re: AB18x5 Breakout Board
« Reply #28 on: January 25, 2017, 05:04:35 PM »
This is probably my last post on this thread, but I thought it might be helpful for others to see what a functioning soldered connection looks like on an AB1805 (see attached).  There are some excess solder balls near the corner of the chip that I  would have cleaned off if it hadn't worked, but since so far all appears to be working correctly, I'm leaving them there for now.  i.e. "if it isn't broken, don't fix it."  In any case, the solder that's where it counts, namely on the pads, is more visibly prominant and correct looking (at least to my eye) than in the photo that I posted earlier of my first attempt with the AB1815, where the connections looked more iffy.  I think going forward this is roughly about what I would be shooting for.

That said, I'd be curious as to how this compares to what others aim for in their soldered connections on this particular AB18x5 chip.
« Last Edit: January 25, 2017, 05:12:40 PM by WhiteHare »

perky

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Re: AB18x5 Breakout Board
« Reply #29 on: January 25, 2017, 05:27:44 PM »
Good work WhiteHare!

BTW I think you've been way over-generous with the solder paste. That's probably the reason for the solder balls, but like you say if it ain't broke..!

Mark.
« Last Edit: January 25, 2017, 07:54:52 PM by perky »