Composites as an Editing Tool
Composites can be used as versatile editing tool in CAM350. They can produce edits superior to those that can done by hand. We will look at Data Inversion and working with Clearances in positive planes.
A composite is a single layer that is made up from multiple layers. Each layer has a polarity (dark vs. clear, not voltage!). A dark layer adds data to the plot and a clear layer removes data. This is often called paint and scratch. Through a combination of these paint and scratch layers, a composite layer is created that will plot the data as you ultimately want it to appear on the film.
To learn more about composites, check your CAM350 help system.
HELP | CONTENTS in CAM350. Open the Tutorial section and select “Composite Layers”.
There are a number of menu items related to composites. We will only focus on
TABLES | COMPOSITES
VIEW | COMPOSITES
UTILITIES | CONVERT COMPOSITES
Invert Data
Using composites, you can change negative data to positive and visa versa. The above is Layer 3 of the standard demo file preview_i.cam. Converting this to a positive layer can be done in 3 steps.
1. Open TABLES | COMPOSITES
Select “Add” button”. This creates a new composite. Select 1 to set the first element of the composite and then choose the layer you want to invert. In this case it is L3. Toggle Bkg (background) to DARK. Element 1 is set to CLEAR.
Press OK.
Nothing will change in the CAM editor. If you want to review your work use VIEW | COMPOSITES.
Everything looks fine. The fact that all background is filled is ok. The convert process will limit this to a 50 mil square around the data. Select VIEW | COMPOSITE again to go back to normal viewing of the database.
You might also see + signs over the voids. This is also nothing to worry about as they are an artifact of padstack designators. They will not translate to the new layer as it is only a graphical process.
Select UTILITIES | CONVERT COMPOSITE then OK. There are options on the screen, but none are relevant to the process, so leave them alone. This will result in a new layer, which is an invert of the original layer.
NOTE: Do not use “COMPOSITES TO LAYER”. It will take longer and there is no trace data for it to preserve. There is no need to use it.
Results are pretty close to what is desired. Note that the area around the board has some extra polygon fill.
This is not a problem, just use EDIT | DELETE and select them to get rid of the extra polygons.
Create new voids in a plane
Composites can also be used to create new voids. In the above example you can add a new layer and put artwork on it for the new void.
TABLES | LAYERS | ADD LAYERS can be used to add your layer.
Add | Flash can be used to add the voids onto the new layer. Below, these flashes are drawn dark red.
Note that any type of artwork can be used on the void layer. You could use Text, Flashes, Lines or polygons.
At this point data on the new layer is positive of course. So we select TABLES | COMPOSTES. Select NEW to create a new Composite. Select the new composite on the left and define as follows.
This time we leave Bkg as clear. We are not trying to invert anything. Element 1 is our positive plane, set DARK. Element 2 is our Void layer set to CLEAR.
OK.
Again you can use View | Composite for a preview. Make sure you select it again to turn off composite view.
Select Utilities | Convert Composite. This time we need to select COMPOSITE_2 in the pull down as it will default to the first composite.
Press OK to create your new layer.
Increase Clearance sizes
OK now that we know how to create a positive from a negative and how to create new voids. What if you want increase the clearance sizes on the positive plane? For this we will need 3 elements. The original layer set as a DARK element, a CLEAR element with oversized pads to create new voids and another DARK element for the pads and traces that are inside the voids. The last part can be difficult.
There are many methods of creating these 3 layers and the best one to use will vary with your data. In this case we will focus on the current example of preview_i and the inverted positive plane we created. Start with creating 2 new layers.
Going back to L3 (our original negative layer) copy the flashes that match up with the clearances you want to increase to the first new layer. In this case I decided to work with just the ones on the right side of the mill out of the board.
Next we need to deal with the thermals. This will have to become rounds for the CLEAR layer and we need to determine the inner diameter as well. Using Query the 2 larger thermals are 100 outer and 75 inner. The smaller ones are 35 and 26.3.
Now Copy the Thermals to the second new layer. Using TABLES | APERTURES add new Dcodes for rounds 100, 75, 35 and 26.3 Mils in size if needed. Next use EDIT | CHANGE | DCODE to change the Thermals on the new layers to Rounds. On the new layer for CLEAR they would be 100 and 35 mils respectively. On the New DARK layer 75 and 26.3 would be used. Results would look like this. Red is the new DARK layer.
Using Utilities | Over/Undersize oversize the CLEAR layer by the desired amount. In this case, 20%. You could use CHANGE | DCODE instead. Editing the aperture table is not recommended unless you are sure the Dcodes are not used anywhere else.
The thermal spokes are a problem too. We had no original data for them, so it will have to be drawn by hand on the new DARK layer. Using a 10 mil round, object snap and ADD | LINE this is easily done.
Besides object snap, adjusting the grid size and using grid snap can help you make cleaner lines. Once completed it would look something like this.
Now setup TABLES | COMPOSITES again. This time we have Composite_3.
After conversion (make sure you select the proper composite on the pull down menu) using Convert Composite we have.
Note that this type of edit can cause unforeseen problems. Running Netlist Compare and DRC processes should follow this kind of work. In the above example on the far right side of the board we have made a problem by using this process.
Dealing with such problems will vary from case to case. In this case going to 90 degree ties with only 3 spokes might be the best answer. Going back and doing more edits to the layers that make up the composite are easy enough to do. Convert again to see the results.
These are only a few examples of what can be done with composites. You might not have an original positive layer to work from. In such cases you could make one using the invert process to make one. Or you could use a drill layer copied to a graphic layer.