Problems with Box Collider 2D

Hi, I did do a pong game , but when i do a speciffic action , the ball get out of the box (the box is the limit) , and i don't know what is happening . this is the code of the raquets , and the ball . I need to do something with Box Collider , where can i found the problem of this "bug" , thanks

Raquets

 using UnityEngine;
 using System.Collections;
 
 public class MoveRacket : MonoBehaviour {
     public float speed = 30;
     public string axis = "Vertical";
 
     void FixedUpdate () {
         float v = Input.GetAxisRaw(axis);
         GetComponent<Rigidbody2D>().velocity = new Vector2(0, v)* speed;
 
     
     }
 }

the ball

 using UnityEngine;
 using System.Collections;
 
 public class Ball : MonoBehaviour
 {
     public float speed = 30;
     
     void Start ()
     {
         // Initial Velocity
         GetComponent<Rigidbody2D> ().velocity = Vector2.right * speed;
     }
 
     void OnCollisionEnter2D (Collision2D col)
     {
 
         if (col.gameObject.name == "RacketLeft") {
             // Calculate hit Factor
             float y = hitFactor (transform.position,
                                 col.transform.position,
                                 col.collider.bounds.size.y);
             Vector2 dir = new Vector2 (1, y).normalized;
 
             GetComponent<Rigidbody2D> ().velocity = dir * speed;
         }
 
         if (col.gameObject.name == "RacketRight") {
 
             float y = hitFactor (transform.position,
                                 col.transform.position,
                                 col.collider.bounds.size.y);
 
             Vector2 dir = new Vector2 (-1, y).normalized;
 
             GetComponent<Rigidbody2D> ().velocity = dir * speed;
         }
     }
 
     float hitFactor (Vector2 ballPos, Vector2 racketPos,
                     float racketHeight)
     {
 
         return (ballPos.y - racketPos.y) / racketHeight;
     }
 }