QFN package and grid problems

Question

Hi All,

I am an Eagle 6.5.0 newbie

I am trying to create a QFN pkg for a TI part. Here are the details.

1) 4 pins on a side with 0.5mm pitch

2) pad size of 0.28x0.85 mm

The problem I am confronting is that all the dimensions are such that I need to constantly change grid resolution. But for example when I create 4 of the pins on a side with 0.5mm grid and change the grid so I can create another side's 4 pins (2.1 mm away), I CANNOT measure that distance since the MARK command only works on grid lines and the pads are not aligned to any grids.

Question 1: What is the proper way to do this when a whole bunch of dimensions are used and require different grid resolutions.

Question 2: Is there a way to create a pad that is round on one end ?

many thanks in advanced.

AnalogNotes · Accepted Answer

For this part, have you tried setting the grid to 0.01mm? I don't know about round pad, maybe someone else can help with that...

autodeskguest · Answer

"Sadry Tavana" < noreply-237344@element14.com > a écrit dans le message de news: 912995212.121394741978168.JavaMail.jive@flcspu-csapp-01.premierfarnell.com ... Hi All, I am an Eagle 6.5.0 newbie I am trying to create a QFN pkg for a TI part. Here are the details. 1) 4 pins on a side with 0.5mm pitch 2) pad size of 0.28x0.85 mm The problem I am confronting is that all the dimensions are such that I need to constantly change grid resolution. But for example when I create 4 of the pins on a side with 0.5mm grid and change the grid so I can create another side's 4 pins (2.1 mm away), I CANNOT measure that distance since the MARK command only works on grid lines and the pads are not aligned to any grids. Question 1: What is the proper way to do this when a whole bunch of dimensions are used and require different grid resolutions. Question 2: Is there a way to create a pad that is round on one end ? many thanks in advanced. 1) You can enter the coords manually for each pad without change the grid. 2) You are probably talking about a "finger pad" You can partially recover your rectangular smd pad with a polygon or a wire See: "Arbitrary Pad Shape" in the PAD section of the EAGLE Help