I've just finished my first component footprint and then I figured out that there is a pad without tCream, which I guess it is generated automatically.
What could be went wrong?
By the way, does it has importance?
Thanks in advance,
Electronic – Missing pad tCream
eaglefootprintsurface-mount
Related Solutions
Simply put, toe and heel are the areas of the solder joint that extend from the front and rear of the lead/pad. Think of a solder pad on your PCB as a piece of paper, and think of your hand as one of the leads coming off an IC package. If you place your hand in the middle of the piece of paper, the "toe" and the "heel" are the distance between the tip of your fingers, and the palm of your hand, to the edges of the paper. That's the extra solder in the joint that extends farther than the actual lead/pad on the IC itself.
Here, they are recommending a specific amount of toe because it will provide mechanical reinforcement for the joint. Since there is no room for a suitable heel, given that this is a castellated package that will sit pretty much flush against the main PCB, the only way to add more solder to the joint is to expand outwards, and thus they recommend to give it some extra toe.
To comply with their recommendations, you'll have to turn off the default stop layer and cream layer for the pads, and draw them by hand. This is as easy as going to the properties for the pads to turn both of those features off, and using the rectangle tool, selected to the tStop and tCream layer, to draw the features.
Based of the picture, it sounds like they recommended a tStop that matches the recommended pad exactly, and a tCream layer that matches the pad exactly except for the edge opposite the package, which would extend out 4 mils further.
Ok, - as everyone is so bashful and decided to answer in the comment - I try to answer myself :) I continued to search for small blue SMD LEDs and I have found that there are just so many different of them available... even for the same package.
So, as venny stated in the comments, I confused bottom view with a real footprint. In the datasheets there are many confusing and not newbie-friendly graphs and patterns.
Not every component has a footprint. But many do. They are included either as Recommended Pad Layout or as Recommended land pattern. A couple of examples of good datasheets for blue SMD 0603 LEDs that do include this information: this and this (first link is especially good; everything is presented in a very neat way). But in case they don't, but do mention the package (0805 or 0603 for instance) then you most probably will be fine with the standard footprints.
And yes, I managed to find LEDs that do need a third pad. This one for example.
Therefore, my conclusion is that one needs to really carefully examine datasheets for each and every part. If there is no pattern for pads, then you should go for a standard pad as Asmyldof mentioned in the comment. Correct me if I'm wrong. Cheers.
Related Topic
- Electronic – Centroid of component for pick and place machine using Eagle
- Electronic – Accidental solder in vias
- Electronic – How to create custom through hole pad shapes in Altium Designer
- Electrical – Altium Designer IPC Footprint wizard error for chip components
- Electronic – Eagle >Label attribute (in some Adafruit parts)
- Altium Collision DRC error? Cant figure out why
Best Answer
If you open the package in the library editor, then right click on the pad in question and select
Properties..., there should be a check box forCream. This has probably become unchecked hence there is no box created on the cream layer. Once you re-enable it a box on the tCream layer will be generated.If you are already using the footprint, you will then in the Layout window need to go to
Library->Update All(alternativelyLibrary->Update...and select just the library you are interested in) to pull the updates into your board design.In terms of importance, it depends on if you are hand soldering the board or using a reflow approach (e.g. having it machine assembled). The
tCreamandbCreamlayers are used to indicate where solder paste will be placed when machine assembling - or more accurately when a solder paste stencil is made.