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How to design PCB Footprint for SMD Transistor

Gopintj1

Hi friends,

      As i am very new to PCB designing using CADENCE Allegro, i would like to know how to design foot print for SMD Transistor which is shown here. As per my knowledge, i have created foot print for micro controlles(QFP) whose pin numbers are same in four faces. But, here, we have only one pin in one direction and two pins in opposite direction.

     Please guide me how to design foot print for this. 

SMD Transistor

Parents
  • ScottCad

    What you could do is create your footprint like this. Instead of using a pin with a padstack for the ground use a "Shape" instead on the etch top layer and another oversize shape for the solder mask for that shape.

    When you place the footprint "Symbol" on your board you can asign a net to the shape for example ground. Then place vias on the shape to tie it into ground if it is a multi layer or 2 layer board.

    Now when you create a symbol in this way that shape will not have any net unlike pins so you would have to remember to asign a net to it during your layout.

    To look at it another way. Assume your compont has 4 leads and a large pad on the back of the part that is to be soldered to the board. Create the 4 leads with traditional pins and padstacks, Create the exposed pad that gets soldered to the board as a shape.

    Hope that helps

    Thanks Scott. 

     

     

Reply
  • ScottCad

    What you could do is create your footprint like this. Instead of using a pin with a padstack for the ground use a "Shape" instead on the etch top layer and another oversize shape for the solder mask for that shape.

    When you place the footprint "Symbol" on your board you can asign a net to the shape for example ground. Then place vias on the shape to tie it into ground if it is a multi layer or 2 layer board.

    Now when you create a symbol in this way that shape will not have any net unlike pins so you would have to remember to asign a net to it during your layout.

    To look at it another way. Assume your compont has 4 leads and a large pad on the back of the part that is to be soldered to the board. Create the 4 leads with traditional pins and padstacks, Create the exposed pad that gets soldered to the board as a shape.

    Hope that helps

    Thanks Scott. 

     

     

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