About LSM330DLC Gyroscopes reflow solder problem

cac2012 · ‎2014-06-10

Posted on June 11, 2014 at 07:32

We used

LSM330DLC Gyroscopes in electric self-balancing unicycle. There is one problem of

LSM330DLC

after

reflow solder.

The

LSM330DLC

has offset to detect

the angle from the vertical direction. The offset may be 0-7 degree, but they are still in good working condition.

I made 1000 units of

LSM330DLC

based controller two times using

reflow solder

.

The ratio is about 15% that has offset problem. Others are good.

How to solve this problem?

Do you think the

LSM330DLC

are

affected by damp?

The caution about

LSM330DLC is as follows.

1.After sealed bag is opened, devices that subjected to reflow solder must

a) mounted within: 168 hours at factory conditions <30

℃/60%RH

b) stored at <10

℃/60%RH

The

LSM330DLC

is not stored with above condition

I really didn't bake them befor

reflow solder.

Do you think the offset problem can be solved if I baked the

LSM330DLC

before

reflow solder?

Thanks

my email is: xmgatech@gmail.com

ivani · ‎2014-06-13

Posted on June 13, 2014 at 12:46

I may be wrong but it could be a normal zero-g offset distribution.

It is stated as 60mg typical value in the datasheet, which usually means that this is 1-sigma value.

In other words only 68% of devices will fit in this number. About 95% will fit within +/-120mg and the rest could go up to +/-180mg (if we assume that ST is not allowing more than 3-sigma deviation of the devices out of the production).

Probably you shall do some zero-g calibration for each board and store it in a NV memory.

Be aware also that it will change with the temperature and might be not fully repeatable from power on to power on cycle.