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Oxford Instruments STM32F103C8T6 Assembly Instructions
Tools required
A temperature-controlled soldering iron with a fine chisel or bevelled conical tip, such as the
TS100
A method of cleaning the tip of the soldering iron such as brass wool or a damp sponge
A pair of fine tip metal tweezers
A small stiff bristled brush such as a tooth brush
A stand mounted magnifying glass or microscope (optional)
An ESD ground strap (optional, but recommended)
Consumables
Approx. 50cm of fine solder wire, 0.5mm works well. 60/40 tin lead solder will give the best
results, especially for a novice. The PCB and components are all lead free and ROHS
compliant. If lead free status is required, a ROHS solder with 5% silver content will yield
better results than standard 100% tin solder.
A synthetic (not rosin based) "no clean" tacky flux such as ChipQuik SMD291. Cheaper
alternatives can be found by searching for "tacky flux" and looking for a flux aimed at BGA
reflow/reball. Rosin based fluxes give off harmful fumes during soldering and should be
avoided unless working with good fume extraction.
De-soldering wick such as Chemtronics soder-wik or Edsyn soldasip
Acetone or isopropyl alcohol (IPA) for washing
Latex or nitrile gloves to be worn during wash operations
Double sided tape to mount the display
ChipQuik de-soldering alloy (optional, needed for rework in case of mistakes)
Step 1 – The Processor
Start with the processor as it is the hardest component to get right. Several attempts may be
required to successfully solder the device, and other parts on the PCB may be damaged by the re-
work process.
Note that the processor is mildly static sensitive. It does have ESD protection diodes built into the
package on all its IO pins, however work should still be conducted wearing an ESD ground strap.
Set the soldering iron for an appropriate temperature for the solder in use. For tin/lead solder, 330°C
is appropriate. For lead free solder, 370°C or higher is required. Thoroughly clean the tip of the
soldering iron by applying some solder and wiping it off, several times if needed. There should be a
shiny spot on the tip of the iron which readily accepts solder. It is important that the soldering iron
tip has a small flat which will hold a small puddle of solder in a controlled location. Conical tips are
not well suited to this task. Chisel tips or conical tips with a bevelled flat on the end are best.
Tin some solder onto 1 or two pins in one corner of the PCB footprint.

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Summary of Contents for Oxford Instruments STM32F103C8T6

  • Page 1 Oxford Instruments STM32F103C8T6 Assembly Instructions Tools required • A temperature-controlled soldering iron with a fine chisel or bevelled conical tip, such as the TS100 • A method of cleaning the tip of the soldering iron such as brass wool or a damp sponge •...
  • Page 2 Place the processor over its correct location on the PCB, making sure to get the orientation and alignment exactly correct. The pin 1 indicator on the package should be at the bottom, matching the white dot on the PCB. With a clean soldering iron tip, bond the pins of the package to the previously tinned pads, ensuring the processor is flat and correctly aligned.
  • Page 3 Thoroughly clean the tip of the soldering iron by applying some solder and wiping it off, several times if needed. Put a small amount of solder on the flat tip of the iron, around 1mm of solder wire. Place this puddle of solder onto one end of one row of pins of the processor and gently wipe it along the row.
  • Page 4 Repeat this process for all 4 sides of the processor, ensuring there are no bridged pins. While wearing gloves, use acetone or IPA and a brush to remove all flux residue from the PCB. Note that the solvent dissolves the flux, however the solvent must then be removed from the PCB using paper towels, otherwise when the solvent flashes off the flux will remain on the PCB.
  • Page 5 Solder down the tab on the top left of the package to ensure it is firmly held in place. Apply flux to the data pins at the base of the package and then apply the soldering iron and a small amount of solder to each pin one at a time.
  • Page 6 Step 3 – The USB Socket Tin the top right pad of the USB socket PCB footprint and position the USB socket correctly over its footprint. Use the soldering iron to stick the USB socket to the tinned pad.
  • Page 7 Solder the top left pad of the USB socket to ensure it is secure. Apply flux to the data pins at the bottom of the package, then apply a small amount of solder to each pin one at a time and then, while wearing gloves, repeat the cleaning process from steps 1 and 2.
  • Page 8 Step 4 – The Linear Regulator & Dual NPN Transistor The Linear regulator (U2) and dual NPN transistor (Q1) are both SOT23 packages and are both soldered in the same way. Tin 1 pad on the PCB footprint of each device, ideally one corner of the package.
  • Page 9 Step 5 – The 8MHz Crystal The crystal (Y1) is non-polarised and may be soldered down in either orientation. The PCB footprint has been designed to make hand soldering easier, however despite this the SMD crystal package can be tricky to solder. The best way to solder this component is to place it onto the untinned pads as shown in the image above.
  • Page 10 Step 6 – The LEDs There are two LEDs on the PCB: the power indicator and the RGB LED controlled by the processor. The same technique as with all other components is followed: tin one pad and stick the component down, then apply the soldering iron and a small amount of solder to each of the remaining pins one at a time.
  • Page 12 Step 7 – Capacitors & Resistors All the capacitors and resistors on the PCB are 0805 SMD packages and are all marked with their reference designators. None of them are polarised, so the orientation is non-critical. The same soldering procedure is followed as will all other parts: tin one pad and stick the component down, then apply the soldering iron and a small amount of solder to the remaining pad.
  • Page 15 The display is sensitive to solvents and therefore should not be washed. Before fitting the display, give the PCB a thorough clean. While wearing gloves, apply a generous amount of acetone or IPA to the PCB and scrub thoroughly with a stiff brush, paying particular attention to the edges of the SD card socket and USB socket.
  • Page 16 Apply some solder to one of the pads and then while holding the display in the correct position, solder one pad down. Once one pad is in place, apply a small amount of flux and then apply the soldering iron and a small amount of solder to the remaining pads. It is advisable to check for short circuits between pins on the display connector after soldering.
  • Page 19 Step 9 – Optional Extras The PCB may be fitted with a power switch, 4 buttons and a battery holder on the reverse side if desired. Three of the buttons may form a user interface (left, right and enter), the 4 is a reset switch which is useful for programming via the USB bootloader.