In trying to have things run smoothly with placement, I have to do a lot of theta adjustment to get the rotation right during placement. Even if the part looks good on the PnP machine screen sometimes it places differently than what is shown.
If I understand it correctly, a chip resistor for example would be created in the layout library horizontally (pad on the left and pad on the right). Then if it is put onto a board layout in the same orientation, then the theta would be zero in the PnP file. So if the part is presented in the feeder in the same orientation, then there is no theta adjustment at the placement level. If the part is rotated 90 in PCB layout, then that 90 is reflected in the PnP file and the placement machine rotates it accordingly from its "zero" state.
I am finding I have to rotate most of the ICs, some of the capacitors, transistors and diodes which takes time during the programming process. I know that some parts are created in the PCB layout library left-right and others are up-down. Now we have been using a new CAD package so there may not be consistency in how the library parts were made. Should they all be consistent and how do you fix it now? Should the PnP profile orientation match the CAD part library orientation?
To make matters worse, some DPAKs for example are presented in the tape horizontally and others are presented vertically, so probably two profiles need to be made accordingly on the PnP machine to handle each presentation. Then purchasing switches vendors and they come in on different orientations or different widths of tape!
How do others out there handle this or do you just grit your teeth and plow through it? Please share your pain.
reply »