Problem...
how does a hobbyist use one of the later generation SMT PICs;
remembering that once soldered there’s no way it's going to be removed
intact, and they aren’t cheap either.
I'm going to describe a carrier arrangement that should allow you to only have to experience the pain on soldering one of these PICs once, and then let you move it around from project to project. The big bonus is that it also allows you to use the PIC on a standard hobbyists breadboard.
I'm going to describe a carrier arrangement that should allow you to only have to experience the pain on soldering one of these PICs once, and then let you move it around from project to project. The big bonus is that it also allows you to use the PIC on a standard hobbyists breadboard.
Completed PIC breadboard adapter.
The above image shows
the completed unit that consists of three PCB's, two of which you can
make yourself but to be honest, I'd buy the main carrier PCB.
Step 1 - Main PIC carrier PCB.
PIC soldered onto carrier board.
This is the main PIC carrier PCB and I bought these pre-etched from Futurlec.
The reason is that it's almost impossible to create such a high quality
PCB in the home workshop and these have solder resist masks which is a
must if you want to be in with a chance of soldering on the PIC. The
boards are dirt cheap (around $0.90 each); it would cost you more for a
piece of double-sided board anyway. First thing to do is solder in 8, 8
pin PCB header plugs; you can get these from Rapid Electronics in
the UK. Using these will allow you to plug the the PCB into the main
carrier board and means that over time, you can create a selection of
these PCB's but still only need one main breadboard carrier board. Also,
if you damage the PIC there's a good chance that you will destroy this
PCB removing it so it limits how much of the complete solution you can
damage.
|
Underside of PIC carrier board.
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Step 2 - Soldering the PIC
Different solder gauges. Top to Bottom, 32swg, 22swg (standard hobbiest), 18 swg
You're going to need to solder on your PIC and I'm afraid your on your own with this.
It's fiddly and you need to really take your time. The only advice I can offer is to use the finest soldering-iron tip you can get (1mm or less), and the finest solder (I use 32swg solder for this type of SMT work).
This is the most difficult bit of the project and once you've done this part, the rest should be plain sailing.
It's fiddly and you need to really take your time. The only advice I can offer is to use the finest soldering-iron tip you can get (1mm or less), and the finest solder (I use 32swg solder for this type of SMT work).
This is the most difficult bit of the project and once you've done this part, the rest should be plain sailing.
Step 3 - Making the main carrier PCB
Carrier board PCB foil with via holes marked
The other two PCB's are fairly straight forward but unfortunately the main vertical carrier PCB is double-sided.
If you've never created double-sided PCB's before don't worry it's not that difficult if your careful and I'll put some notes up here in a little while with some instructions.
Whilst its double-sided, we can't have thru-plated holes (at least, not simply) and we need to solder in some sockets that will accept the pins from our Futurlec PCB, and it's a bit trickier if the holes aren’t thru-plated. So, to get around this limitation I added via points next to the socket holes. All you need to do is insert a piece of wire through the hole and solder it on both sides. The vias are shown with yellow borders around them.
You will notice that there is provision on the board for a standard Crystal and two loading capacitors. It's up to you if you install these !
If you've never created double-sided PCB's before don't worry it's not that difficult if your careful and I'll put some notes up here in a little while with some instructions.
Whilst its double-sided, we can't have thru-plated holes (at least, not simply) and we need to solder in some sockets that will accept the pins from our Futurlec PCB, and it's a bit trickier if the holes aren’t thru-plated. So, to get around this limitation I added via points next to the socket holes. All you need to do is insert a piece of wire through the hole and solder it on both sides. The vias are shown with yellow borders around them.
You will notice that there is provision on the board for a standard Crystal and two loading capacitors. It's up to you if you install these !
Step 4 - Making the breadboard conector PCB
Breadboard connector PCB foil.
The
breadboard connector PCB is very simple to make and you should be able
to use an off-cut of PCB laminate for this. You will notice that as well
as the two main rows of 32 x holes, there are 8 additional holes. I
added these to that you can fit Vero pins and these can be used to trap
the main carrier PCB in position to make soldering simpler.
The 64 pins used should be turned-pin types. If you use standard square pins (as used on the main PIC board), they are too tight a fit in to the breadboard and even if you did manage to insert the module, you would be hard pressed to remove it intact. The turned-pin types whilst more expensive and fragile, offer a better fit for applications that require lots of pins. |
Underside of the carrier PCB showing the two rows of turned-pin headers.
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Step 5 - Bringing it all together
Main carrier PCB soldered to the breadboard connector PCB.
Trap
the main carrier PCB between the Vero pins fixed into the breadboard
connector PCB making sure that every aligns correctly, then start to
solder.
I held the assembly in a set of "helping-hands" at an angle that gave me best access to where each solder joint was to be made.
Move carefully and slowly from one joint to the next allowing a couple of seconds between each join for the previous joint to completely cool (if you move too fast you end up with solder bridges all over the place).
The last task is to print a legend to identify the numbers and locations of the pins.
I held the assembly in a set of "helping-hands" at an angle that gave me best access to where each solder joint was to be made.
Move carefully and slowly from one joint to the next allowing a couple of seconds between each join for the previous joint to completely cool (if you move too fast you end up with solder bridges all over the place).
The last task is to print a legend to identify the numbers and locations of the pins.
Final board mounted on a breadboard and connected to a PicKit 3.
I've been using this carrier board for a while now (running the PIC with a 16MHz crystal) and not had any problems... so far...
There's a link to a ZIP file below that contains an Excel spreadsheet with the legends text, and a PCB foil file for DipTrace (you can download a copy for free from their website).
If you have any comments or questions, please just drop me a line.
There's a link to a ZIP file below that contains an Excel spreadsheet with the legends text, and a PCB foil file for DipTrace (you can download a copy for free from their website).
If you have any comments or questions, please just drop me a line.
| 18f65k22-v2.zip |
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