footprint of a component

[electricity86]

Hello,
I was asked to find out the footprint of a capacitor.
In the datasheet, it said the the 'DxL' of the capacitor is 6.3x11 (mm)
I derive from that the Dimater of the capacitor which is 6.3 mm and the length of the capacitor which is 11 mm.
What is the footprint of this capacitor?
6.3x11 isnt exactly the area of the capacitor if the capacitor is round-shaped.

The mentioned capacitor can be found here:
https://www.electro-tech-online.com/custompdfs/2009/01/e-pm.pdf

Thanks!

 

[KMoffett]

On a printed circuit board the footprint of this capacitor, normally vertically mounted, would be a circle 6.3mm in diameter.

Ken

 

[Boncuk]

That kind of capacitor doesn't have a footprint. Moreover it has two solder pads spaced 2.5 to 5.08mm (as far as I can remember from the glance on the data sheet)

The only interesting part to place that kind of component on your PCB are three dimensions: a) part diameter b) pin spacing c) pin diameter. The overall height is only necessary if you want to place the cap horizontally.

E.g. part diameter 6.3mm (circle 3.15mm radius), pin spacing 2.5mm and pin diameter 0.6mm. The latter require a pad size of 1.6mm and a drill of 0.65mm (to compensate for copper buildup in the drill hole after electrochemical through contacting process)

Boncuk

 

[KMoffett]

That kind of capacitor doesn't have a footprint. .....
Boncuk

What would you call the image you posted? All the PCB layout programs I've seen refer to that as a "footprint" on the board of a radial-lead polarized capacitor of specific diameter and pin spacing dimensions...electricity86's cap. If it had a different diameter or lead spacing it would have a different footprint. Or, we just using different terminology?

Ken

 

[electricity86]

Thanks a lot guys!
I learned a lot.

Could you please tell me what does it mean when next to a part, it says:
0.24
-----
0.26
(the line should be continuous, like 0.26 divided into 0.24)
what is its meaning?

thanks.

 

[xanadunow]

In a standard design, the "foot print" is simply the amount of space the capacitor occupies on the PCB + the space required to "fit" the end wires.

As in this example the ends of that cap do fit inside the overall diameter of this vertically mounted capacitor as Boncuk stated, the foot print becomes the outer diameter of the cap to place other components around it plus the two holes within that diameter). They all have to fit on the pcb.

The "foot print" is all that you see when you place a component on the PCB (the x times y space it occupies). The "foot print" is a combination of the XY space plus the electrical connecting points for the PCB design purpose.

Think of two identical resistors mounted "one horizontally" and the other resistor mounted "vertically".. the footprint is different; in a vertical solution you have saved some xy space on the board, but you have increased the height of the whole module the PCB is designed for.

It is your choice as a designer of the PCB to choose the "foot print", you do know how the component will be mounted.

In the example of the capacitor you have mentioned, you could solder the capacitor some few milimeters off the board and still fit some components underneath the space occupied by its diameter, it would be a pretty odd design but I use it as an example to show that if you did design the PCB in this way - the "footprint" for that capacitor, would be just the two holes the capacitor does fit into..

xanadunow

 

[xanadunow]

not enough information electricity86 .. post a picture or make more comments please.. what kind of component is it.. what are other markings on it?

 

[igorhtm]

It may be width of trace..

 

[electricity86]

here is the picture:
ImageShack - Image Hosting :: quesni1.gif

Thanks alot!

**broken link removed**

 

[ormo]

here is the picture:
ImageShack - Image Hosting :: quesni1.gif

Thanks alot!

**broken link removed**

Looks like some kind of surface-mount integrated circuit (IC). As for what IC it is, do you have a part number/model number?

 

[electricity86]

Looks like some kind of surface-mount integrated circuit (IC). As for what IC it is, do you have a part number/model number?

The device itself is not the point of interest.
I wanted to know what does it mean the symbolizing:
6.2
----
5.8

4
---
3.8
etc.

 

[KMoffett]

electricity86,

Can you provide a link to the document that you are looking at?

Ken

 

[electricity86]

Yes of course.
Here is the datasheet of the component:
http://www.sst.com/downloads/datasheet/S71265.pdf
The picture is taken from page 24.

Thanks,
Shahar.

 

[KMoffett]

Note 1. on page 25. Looks like these are the minimum and maximum expected lengths of these dimensions, in millimeters.

Ken

 

[electricity86]

you're right.
Thank you very much!

Shahar

 

[Boncuk]

Or, we just using different terminology?

Ken

We certainly do. I refer to footprints when using SMT.

Hans

 

[Boncuk]

The device itself is not the point of interest.
I wanted to know what does it mean the symbolizing:
6.2
----
5.8

4
---
3.8
etc.

the two numbers (respectivley each pair of numbers) are given for the body size of a component. In that case the body lenght might vary between 5.8 and 6.2mm (with a nominal length of 6.0mm - averaging 6.2 and 5.8).

The pin distance is always the most accurate value given in data sheets and doesn't have a minimum or maximum. The pin length might vary though. Using the largest outer size for the footprint the component should fit onto the PCB design.