Introduction

After analysis of the chips on the MiniMed 530G PCBs, we determined that in order to pull data from the Cyprus static RAM chip, we would most likely need to remove the chip from the PCB and solder wires to it in order to connect it to an Arduino board. This would allow us to create and utilize an Arduino program that would configure the connected pins in a way that would allow us to read all data from the chip.

Removing a Chip

The first step was learning how to remove a chip from a PCB. This process is detailed below:

Step 1: Place PCB on frame above hot plate and secure in place. The PCB should not be able to move around during this process.

Step 2: Turn on the hot plate and preheat it to 200-300 degrees Celsius. Wait for the plate to heat up completely before continuing.

Step 3: Apply flux liberally to the chip being removed.

Step 4: Turn on the hot air gun and heat it to 300-500 degrees Celsius. Take the hot air gun and circle it slowly around the chip, pointing it at the sides. Do this for several minutes.

Step 5: Take tweezers and attempt to move the chip. If it's ready to come off, it will move easily. Once the chip has started moving, remove it immediately to avoid it resoldering to the board in the wrong position. If the chip does not move, continue heating it with the hot air gun and applying flux. Retry every few minutes.

Soldering

The next step was learning how to solder. Working with the IoT team at the Leahy Center (specifically Tom), I learned how to solder properly with the help of a microscope. This process is detailed below:

Step 1: Gather equipment necessary. This includes protective equipment (gloves, goggles, respirator), fume extractor, flux, lead solder, wires, isopropyl, brush, solder wick, and the chip.

Step 2: Prep the station. Equip protective gear. Stick the chip to the table with double-sided tape. Position microscope over chip. Bring fume extractor close and turn on. Turn on soldering iron. Apply flux liberally to the chip. Cut appropriate length of wire.

Step 3: Solder. Remove soldering iron and gently touch to the end of the lead solder, gathering a small amount on the tip of the iron. Position the wire in one hand and the iron in the other close to the pin being soldered, then look through the microscope. Hold the tip of the wire to the pin, then bring the iron with the lead solder down to press the wire to the pin. Keep tapping and adjusting as necessary until the tip of the wire is fully attached to the pin and does not touch any other pins. The wire should be able to withstand being pulled from the other end without disconnecting from the chip. Apply more flux if needed. If soldering multiple pins, start with the pin highest up on the chip and furthest away from the hand holding the soldering iron.

Step 5: Cleanup. Tape all attached wires down to the table. Take the solder wick and press a clean length of it to the points on the chip where solder needs to be removed. Press the soldering iron against the wick and move both the iron and the wick together across the chip slowly, until no resistance is felt. Douse the chip in isopropyl alcohol, and gently use the brush to get rid of any remaining flux.

Steps Taken

So far, I have practiced soldering to the point where I am comfortable with microsoldering. I have also removed the static RAM chip and am prepared to solder it.