Is the correct sentence has become or became?

The correct choice depends on the context and the tense you are trying to convey.

* "Has become" is the present perfect tense, used to describe an action that started in the past and continues to the present or has a result that affects the present.

* Example: "The weather has become much colder recently."

* "Became" is the past tense, used to describe an action that happened in the past.

* Example: "The weather became colder after the sun went down."

Can you give me the full sentence you are trying to write? This will help me determine the correct verb choice.