There could be several reasons why the upper thread keeps breaking.
Check the following points or issues.

• The needle is not correctly installed. Correctly install the needle.
   
• The needle is bent or blunt. Replace the needle with a new one.
   
• The area around the embroidery foot hole is damaged.
   

  (1) Scratches/Burrs

  
  Replace the presser foot. Consult your nearest authorized Brother dealer.
   
• There are knots or tangles in the thread. Remove any knots or tangles.
   
• The upper thread tension is too high. Decrease the upper thread tension.
   
• The bobbin case is damaged. Replace the bobbin case with a new one.
   
• A bobbin designed specifically for this machine is not used. Use the correct bobbin.
   
• The needle set screw is loose. Use the Allen screw driver to tighten the needle set screw.
   
• The area around the hole in the needle plate is damaged.
   

  (1) Scratches/Burrs

  
  Replace the needle plate or consult your nearest authorized Brother dealer.
   
• The needle is touching the needle plate
   

  (1) Needle (2) Needle plate hole (3) Needle touching hole

  
  Consult your nearest authorized Brother dealer.
   
• The presser foot is set too high and not correctly positioned. The needle hits/touches the presser foot.
  Consult your nearest authorized Brother dealer.
   
• Using a weak thread like a metallic thread. Slow down the machine embroidering speed.
   
• Sliding surface on hook is not smooth. There are burns on it.
   

  (1) Hook race area

  
  Consult your nearest authorized Brother dealer.
   
• The thread is loose in the hook area. Remove the loose thread. If the thread is tangled in the hook, clean the hook.
   
• The play between the hook and the race is too much. Consult your nearest authorized Brother dealer.
   
• The hook does not rotate smoothly. Remove lint, clean and apply oil.
   
• The space between the hook stopper and the hook cannot be adjusted.
  Consult your nearest authorized Brother dealer.
   
• The upper thread is not threaded correctly.
    Pull the upper thread by hand from below the presser foot, and check that the thread moves smoothly. If the thread does not move smoothly, it is not correctly threaded. Unthread the machine and rethread the machine. Make sure the thread is correctly positioned in the needle bar thread guide.

  For details, see "Upper threading" .
   

• Upper thread is not positioned in upper or middle guide plate.
  Make sure thread passes completely under upper and middle guide plate.
   
• The lower thread tension is incorrect. The thread does not roll out of the bobbin case smoothly.
  Adjust the lower thread tension.
   
• The bobbin thread is not wound correctly.
  Check that the bobbin is wound so that it is about 80% full and that the thread is evenly wound.
  If the bobbin is not correctly wound, replace the bobbin with one that is correctly wound or rewind the bobbin.
   
• The automatic threading mechanism is broken. Consult your nearest authorized Brother dealer.
   
• Adhesive is attached to the needle. Replace the needle.
   
• The fabric is not taut. Firmly set the fabric in the embroidery frame so that it is taut.
   
• The thread quality is poor. The thread quality is too weak due to age of thread. Replace thread.
   
• The thread density of the embroidery data is too fine. Three or more overlapping stitches are being sewn.
  Using a data design system, correct the thread density and overstitching settings in the embroidery data.