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Placement theta (rotation) adjustment

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Placement theta (rotation) adjustment | 12 September, 2017

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.

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Placement theta (rotation) adjustment | 13 September, 2017

Here are the basics for theta issues in teaching:

1. CAD part library should match machine part library orientation. 2. If your placement orientation is correct and your feeding orientation(orientation in your feeder) is correct, there should be no issue with placement. If you see different, one of these orientations is wrong. 3.There are different orientations in tape by manufacturers as well as different tape sizes. you could fix that each time you change to a different kind of tape packaging(that should reflect only the feeder orientation settings) or you can have separate part numbers for each, or separate feeder loadings(whatever your machine software allows you to do.)

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Placement theta (rotation) adjustment | 18 September, 2017

As Evitomov says, provided you check everything is setup correctly there should be no issue. There can be some variation between manufacturers as to how they package certain components. For example 2512 resistors are usually in 12mm tape with a 4mm spacing but some manufactueres like to use 8mm spacing (resulting in a much more robust tape). Different machines will have software that handles this differently. In our case Feedertypes are assigned to a specific part number rather than package type and I can define multiple feedertypes for a given partnumber e.g tube, short tape holder 4mm spacing 8mm spacing. When I assign a part to a feeder and that offers multiple possibilities the machine will prompt me as to which type I am loading. When creating your part definitions it is usually a good idea to check the datasheet for packaging and orientation information, some provide it, some seemingly don't. In the cases where they don't you will just have to wait for some parts to look at.

The orientation of most parts is pretty predictable, IME only IR puts DPAKS the other way around to everyone else. QFNs are far less predictable...

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