Because is a subordinating conjunction. It shows the cause. So is a coordinating conjunction. It shows the effect.
We can combine two clauses using because and so.
Study the example given below.
Susie didn’t attend the party. She was not invited.
We can combine these two clauses in two different ways.
Susie didn’t attend the party because she was not invited.
Susie was not invited, so she did not attend the party.