Hello,
I am prototyping with the MPU6050 chip and get a negative gyro bias of roughly 4 to 5 deg/s on my x-axis rotation when the chip is stationary. The gyro bias on the y and z axis are much smaller, roughly 0.5 deg/s. All three axis of the gyros pass the self test. The datasheet section 11.4.1 discusses thermal stressing that can cause gyro bias. I suspect that is causing the problem. I used a hot air station to hand solder the mpu6050 chip. I would appreciate it if someone could clarify the following questions I have:
What does the following two sentences mean in terms of practical PCB design?
Traces connected to pads must be symmetric as possible. Maximizing symmetry and balance for pad connection will help component self alignment and will lead to better control of solder paste reduction after reflow.
How does use of leaded solder effect the gyro readings? There is no explanation for it in the datasheet. I use leaded solder for prototyping since it is much easier to deal with.
11.4.1 Gyroscope Surface Mount Guidelines
InvenSense MEMS Gyros sense rate of rotation. In addition, gyroscopes sense mechanical stress coming
from the printed circuit board (PCB). This PCB stress can be minimized by adhering to certain design rules:
When using MEMS gyroscope components in plastic packages, PCB mounting and assembly can cause
package stress. This package stress in turn can affect the output offset and its value over a wide range of
temperatures. This stress is caused by the mismatch between the Coefficient of Linear Thermal Expansion
(CTE) of the package material and the PCB. Care must be taken to avoid package stress due to mounting.
Traces connected to pads should be as symmetric as possible. Maximizing symmetry and balance for pad
connection will help component self alignment and will lead to better control of solder paste reduction after
reflow.
Any material used in the surface mount assembly process of the MEMS gyroscope should be free of
restricted RoHS elements or compounds. Pb-free solders should be used for assembly.