Introduction: PIC & AVR Modules From SMD Chips Suited for BreadBoarding
From Time to time, you would come across some micro-controllers in Surface mounted (SMD ) Form, that you would like to try out on your breadboard ! You would try hard to get the DIL version of that chip, sometimes it would not be available. Latest versions of MCU chips are almost always produced in SMD form, could be SOIC, or SOP or TSSOP, QFP of TQFP (quad form). This Instructable is to fill in that need of the hobbyist tinkerer.
I came across some SMD chips for PIC16F76 - SOIC 28. Bought a bunch of them for cheap. More bang for the buck!
Also I came across some SMD chips for Atmega88A-AU in 32 Lead TQFP form. This is a quad package having 8 pins on each of the 4 sides. And some SMD chips for the ATTINY44A - 14-pin 0.8mm pitch TSSOP (it just covers the top of your thumb!). These were a challenge, i will show you what to do with them in the next instructable.
First we will look at the easier to handle SOIC28- PIC16F76. See the strip package it comes in (picture 1).
And what we did with it to finally to place it on the breadboard, from where you hobbyists can start playing, plugging in all the components you like on the generously available pins ! see Pic 2.
Another reason why you might want to do this kind of thing is the SMD versions if you buy 10 of them or sometimes 5 on a chinese site work out much cheaper than the DIP type version from your friendly neighbourhood electronics store, if you can wait 3 weeks to receive it in the trans-continent shipping system.
Step 1: Making the SOIC 28pin 1.27mm Pitch PIC16F76 Module
These are the tools you need, a wire-snippers, 0.5mm diameter steel wire (get it from any hardware store, its used for tying steel rebars, you need the steel wire as it needs to be stiff enough, sometimes comes with a light zinc coating), a TSSOP adapter board available from any online electronics store., and a ruler (if you have problems cutting the wire lengths exactly by eye). Also machine header male pins are useful to align the snipped wire lengths during working. Two headers each having 14 pins are needed. They will be used as Jigs to hold the pins while you place them into the holes of the adapter later and while soldering. You Could use 0.6mm steel wire too, which may better suit our breadboard insertion finally, but I didn't have access to this wire size.
Please see the pics.
You need to use a 3M commonly used in kitchen green Scrub pad, Use this to clean a 1 meter stretch of the 0.5 mm wire to make it shine, swipe the wire from end to end (don't cut it yet from the spool on which you have stored the wire) 3 times or more until it gains a lustre that you can see. a few light brown rust spots on the wire may be seen, just wipe with the scrub pad on them too. Its all right if you can't remove all of them fully, as long as the ends of the wires are shiny. This wire cleaning step is necessary. While doing this, stretch the wire slightly, to even out any kinks or bends in it so its reasonable straight before we start snipping. If any kink in the wire is unrectifiable, reject that small portion while doing the snipping as per act in the next paragraph.
Start snipping from the cleaned wire in 2 inch lengths. Use an already snipped wire to measure the next wire length to be snipped, its OK if they are off-length by upto 1 or 2 mm. After soldering finally , still you can resize or snip the ones that are longer and even them out. You need 28 of them , make 4 extra in case you find some defects while soldering in any snipped piece, to replace it. Lay them down on a white paper in your worktable neatly each parallel to the other.
Step 2: Soldering the SOIC28 SMD Chip to Adapter
Now pick up the SOIC 28 adapter, Usually it may have two sides, you will use the side having 1.27mm pitch between tracks (other side could be TSSOP or SSOP28 with 0.65mm pitch ). Sometimes you will be able to
source SOIC 32 , its alright, as long as its more than 28. You can use those also, Just leave the holes that you don't need for your SMD chip unused. However Place the chip to uppermost position, on the adapter, aligning its pin no. 1 with the pin 1 marking on the adapter board, (unused pads below. There will be a dot on the chip to mark the pin no. 1. The writing on the adapter saying "SOIC-28" should come below the chip, ie, below pins 14 and 15. This writing on the adapter helps you to recognize how to position the chip later on when handling the module and plugging into breadboard, removing and doing it repeatedly in future, without errors.
Clean the adapter tracks and edge VIAs too with the green scotch-brite pad, no need to overdo it ! Place some flux on the pads of the adapter where you will solder. Place flux on top of the MCU pins on top for 1mm only along the pin, that is at the very end of the pin. Place the MCU on the adapter. You can use a piece of 3M masking tape to hold it in place until you solder a few pins at the corners of the chip, to firmly anchor it, then remove the tape and solder the rest. Its important to take some time to align the chip correctly so that its pins sit on the adapter tracks as far as possible bang in the centre and then fix the masking tape. While soldering the pins use the smallest amount of solder possible at the tip of the Iron (I use a conical fine tip 10 watt iron, TIP: ALWAYS use a Temperature controlled Iron either manual or automatic type with Mains isolation/ Tranformer type when working with sensitive electronics/ microcontrollers, LEDs etc) or 1mm just above the tip, so it flows down to the tip as you hold it against each pin tip. 0.5mm diameter multicore flux solder wire is suitable. You can also use 0.8mm solder wire if you are careful to dab just a teeny tiny bit at end of each pin with the tip of the iron at the right temperature. The solder will flow just under each pad as you dab or touch the Iron tip at each pin, holding it to the tracks/ pads on the Adapter. You can normally dab and anchor solder 3 pins each time you touch your Iron's tip to the solder wire (to melt a bit of it onto the tip or 1mm above the tip, as it will tend to flow DOWN on a conical tip, which is what you need). And repeat for the next 3 pins in sequence. Later on you can come back and give one more dab with a small amount of solder, on the ends of the pins where you have a doubt about connectivity, but never place excess solder in first place, as it will bridge the contact pins of the MCU, you would lose much time in removing this excess solder with a solder sucker, not to mention overheating the Adapter Pads , tracks and MCU pins). Looks at some U-tube SMD soldering tutorials if you are not confident, and practice with an expendable SMD or PCB before you attempt this on a real MCU !
After cooling, place the DMM on continuity range and listen to the beep as you check the VIA at each hole on the periphery of the adapter with the other probe tip placed gently on each and every pin of the MCU ! Yes, its only 1.27mm pitch between the MCU pns, but you can place the probe on the right pin ! You can do it with 0.8mm pitch SMD MCU and QFP too (later instructable) ! Its only a continuity check so a brief sojourn of DMM probe tip on each pin of MCU lightly touching it from TOP with probe held vertically, listening for the beep will do. the trick The holes / VIAS in the adapter help you in anchoring the other probe tip of your DMM. Ensure the continuity is there for the corresponding VIAs in the SOIC Adapter to the MCU pins. Repeat if in doubt. Do it starting from PIN1 (it is marked on the adapter VIA holes) and finish at pin 28 in order so you don't miss any pin or hole). Look carefully for bridged pins , using a lens if you wish, while you do this, and do continuity check on adjacent pin too to ensure there is no bridging between ANY TWO adjacent pins. Any Slight bridging you can correct by placing the iron tip on it, remelting it and pulling outwards in the gap between the two MCU pins. If this dosen't correct the bridging, obviously its a bigger glob you are dealing with (you didn't observe the rule of 'minimum solder' to be used!) and bring your solder sucker or braid wire, whichever you like to use.
This continuity check for bridging possibility can be done at the periphery too since you already checked from the edge pads / VIA holes to MCU individual pins for continuity in previous step ! Just check continuity from one VIA hole to its neighbor ! It shouldn't beep !. Hope my explanation is fairly detailed enough to help even the beginner.
Then after completing this to your satisfaction, go to the act of soldering wire pieces to the VIA holes in the edges of adapter (next step).
Step 3: Position the Snipped Wire Pieces Into Adapter Holes and Solder
Place each wire piece you snipped carefully into each hole of the SOIC-28
adapter until it comes to rest in the guide hole below inside the machine pins header. hold the machine pins header at a distance below the adapter so that exactly one inch protrudes for each wire you insert below the adapter hole. This is how I did it. The machine pins header is just tight enough to receive the 0.5mm wire bit, a correct fit and holds it in place while you place other pins too into remaining holes. Do one side of the SOIC adapter first, ie, 14 wire bits will be introduced on one side first thru the adapter holes. All wire bits should go tightly into the machine header held one inch below (Push each wire piece end into the hole in the machine header) it in exactly parallel position, as far as you can see its parallel by eye, below it ! It looks difficult, but isn't, just keep doing it one wire bit at a time.
Finally place flux using a tiny brush on the Via holes thru which the wire pieces pass. More flux is always good, you can always clean up later with IPA. Place some flux on the wire too which is near the adapter hole, a mm above and below it. Warm up your soldering Iron and start soldering. Solder on top and bottom of the Via holes, so you get nice pointed conical solder joints on the holes and wires passing through. Its not as difficult as it sounds ! If you have not done it before, you will get it easily, just use enough flux if you find you have solder not fusing properly either with the pad or the steel wire. Further TIPS: Do not use too high Iron temperature, as that will cause the flux to evaporate before it has done its job ! Also reduce the Iron temperature by turning its regulator (manual temperature controlled iron needs this, but those of you who have automatic irons too need to set the lowest temperature that STILL MELTS THE SOLDER reliably, to avoid overheating, pad de-lamination, and flux premature evaporation) until the heat is just enough to do your job while soldering and fusing the wire lengths to the Via holes in the adapter.
After completing the above, repeat with the other machine pin header held below the holes of adapter , using the remaining 14 wire bits on the other side, and solder. (TIP: We are using the 14-pin machine pins header as a 'JIG & FIXTURE' to help us to hold the pins equi-spaced, ends positioned at right distance, and then soldering, one wire at a time. Make sure before soldering the pins that the JIG and adapter PCB are at right distance apart (each pin should protrude at least one inch below the adapter board) and as parallel as you can make it.) In above pics you will see chip is not soldered onto the adapter, because its shown for demonstration purposes, but you must solder the SMD chip onto adapter first before soldering the wire bits or pins through the adapter's holes/ VIAs ! (One chip I already soldered and the pics for that you can see next step.)
Step 4: The Completed DIL MCU Package Ready for Using on Breadboard ! and for DuPont Jumpers Too !
You can see the pics showing the completed module. You can place it on any breadboard and connect components as you wish while experimenting on this MCU.
Notice that in addition to the breadboard holes, you can also use the top wire projections (above the adapter PCB) to connect female DuPont type jumper wire connectors ! This can help you to avoid wire congestion. In this way it gives you added flexibilty in using this module. The 0.5mm wire we used works for snug fit to the DuPont Jumpers too ! I normally place this Module on the Breadboard, most of the connections to the pins are made on the breadboard pin sockets except the Vcc and Ground I connect directly with DuPont jumpers on TOP OF THE MODULE. In case you are testing one digital pin with an LED you can connect this LED with a resistor directly to one of the top pins if you don't have space left on the breadboard. So we can make connections in two layers to this adapter board ! Measuring voltage at pins is also easy, just connect the DMM black probe to ground pin and other red probe to the pin where you want to measure , using the top projecting pins for measuring the voltage (eg, PWM voltage on a pin, Digital ON state of a pin etc).
Step 5: Some More Photos to Understand What We Did.
Further photos will help you to understand the process and finally what we obtained, suitable to plug into our breadboard. Note that there are two ways of using it in breadboard, you can plug it straight in without removing the Machine Male header pins on either side (14 pin header on either side) which are still fitting snugly into the wires coming down from the adapter holding out MCU ! or you can carefully remove the headers, making sure the pins are spaced equally 0.1 inch apart and plug the 0.5mm dia steel wire ends into the breadboard. Be sure to straighten all the pins with a needle nose pliers after the soldering process of wires to adapter is complete, maintaining even spacing between pins at their top end above adapter board and at bottom end where it goes into the breadboard. But I use it with the header pins in place, as they help in alignment of the stiff wires which fit snug into the header holes.
Its your choice, whichever you feel comfortable with.
Step 6: Module for SOIC 0.8mm Pitch Attiny44A
I provide only the pics for the packages I made for experimenting on the Attiny44A and 32-pin QFP Atmega 88A. I will describe how to do it in later instructable. They are soldered on their own removable Plug-in module, with corresponding sockets (female jumper pin headers) soldered on a quick programming cum development board I made from stripboard, which also contains the 10 pin ICS header from the USB-ASP. for convenience in programming.
Step 7: Plug-in Module for 32pin-TQFP Package Atmega88A-SSU, Pics Only With Development Board to Use It
See the pics enclosed., I do not give description of process in this instructable, but its very similar to the one described for creation of removable module containing the MCU. The 10 pin ICS header is also shown. There is a power indicating LED on each board. Also a reverse voltage prevention Schottky with Vfw 0.24V on the board shown in these pics. I normally place these on every board I create from stripboard.
There is also a RESET pin button to ground it, and a 4.7 K resistor for pull-up of this pin to Vcc. This reset resistor is needed not only for MCU normal operation but for programming it too. The USB-ASP will pull the RESET pin to GROUND potential, whereupon the pins MISO, MOSI, SCK, will stop behaving as Port pins and take up their 'alternate functions' to carry out SPI protocol (ICS function). When RESET pin is held high by the USB-ASP these same pins function in their normal mode as Port Pins. This may help you to understand better how these same pins work in two different ways, one while programming, other while doing normal operation as port pins, and why RESET pin bit should be set to 1 to "allow" it to be used for Reset purpose instead of Port pin, and why SPIEN bit in Fuses should be set (value '0') to enable ICS/ programming with SPI pins of MCU function..
All these boards described with photos, I have made and tested and have run programs of various types, reliably.
The white socket you see is for taking a 6 pin connector off from the development -programming board effectively working as a 10 pin ICS to 6 pin ICS header. More on this later. The Male socket that plugs into this white socket contains leads that terminate in DuPont type female jumpers that you can slide on top of the wires projecting from any module you have made so far, onto the ICS pins, so that you can program them easily without placing them on a breadboard !
Happy Experimenting !
Now SMD chips and MCUs are not a limitation to your journeys. into exciting Microcontroller horizons. It remains or rests on your project ideas and programming skills now !
I look forward to your comments, and remarks below, on this write-up, and knowing about other ways you may have been using to make SMD chips usable by hobbyists.