I have a BLDC motor controller that uses a high side 0.001 ohm current sense resistor (CSS2H-5930K-1L00F) and a MAX40201FAUA (50 V/V) to measure the current during motor operation via a Teensy 3.6 ADC. I am trying to calibrate the current sense hardware to the Teensy 3.6 microcontroller, but I am having issues with the MAX40201 outputting values way too high for the known current passing through the resistor. I measured voltages on each side of the resistor with my oscilloscope and it showed a voltage drop of 30-80 mV for a 2.5 A known load across the 0.001 ohm resistor!
So I am thinking that the solder joint is bad. During soldering, I used a stencil and a rework gun to solder the SMD components. For the high amperage traces, I later added higher temp silver bearing solder with a hand soldering iron to reinforce them. I thought this would help the traces hold up to the high intermittent current.
Since my process apparently led to either incomplete fusion of the large flat current sense resistor or capturing flux between the resistor and the PCB, what is the best method for hand soldering these types of components so as to minimize joint resistance?
Image of the PCB section housing the 0.001 ohm resistor: