SMD pad sizes in rcl.lib (Kemet vs non)

On Tue, 28 Sep 2010, Robert Palmer wrote to us saying :

>Other than the obvious size difference, what is the functional difference

>between the Kemet packages and the non-kemet in the rcl.lib.  Specifically,

>I'm looking at the 0402 and the 0402K for capacitors and resistors.  When

>would I use one vs the other?  Why are there two different packages for

>0402?

The 0402 refers to the size of the actual component. This size is

standard, and all 0402 parts are the same size. However, this is not the

same as the size of the PCB footprint because the pads have to be large

enough to allow the ends of the component to be soldered. Component

manufacturers recommend a PCB footprint to use, which is sometimes

different depending on whether you will be using wave or reflow

soldering. As it happens, most manufacturers recommend the same pad size

and spacing for their 0402 capacitors. For some reason Kemet recommend a

different one.

The best thing is to check the data sheet for the actual components

you're using and see whether it recommends the Kemet pads or the more

common ones. If they're free issued by your board house (as my preferred

board house do for common resistors and ceramic caps) then check with

them as to which footprint they prefer.

--

Rob Pearce                       http://www.bdt-home.demon.co.uk

The contents of     | Pickle's Law:

this message are    |   If Congress must do a painful thing,

purely my opinion.  |   the thing must be done in an odd-number year.

Don't believe a     |

word.               |

On Tue, 28 Sep 2010, Robert Palmer wrote to us saying :

>Other than the obvious size difference, what is the functional difference

>between the Kemet packages and the non-kemet in the rcl.lib.  Specifically,

>I'm looking at the 0402 and the 0402K for capacitors and resistors.  When

>would I use one vs the other?  Why are there two different packages for

>0402?

The 0402 refers to the size of the actual component. This size is

standard, and all 0402 parts are the same size. However, this is not the

same as the size of the PCB footprint because the pads have to be large

enough to allow the ends of the component to be soldered. Component

manufacturers recommend a PCB footprint to use, which is sometimes

different depending on whether you will be using wave or reflow

soldering. As it happens, most manufacturers recommend the same pad size

and spacing for their 0402 capacitors. For some reason Kemet recommend a

different one.

The best thing is to check the data sheet for the actual components

you're using and see whether it recommends the Kemet pads or the more

common ones. If they're free issued by your board house (as my preferred

board house do for common resistors and ceramic caps) then check with

them as to which footprint they prefer.

--

Rob Pearce                       http://www.bdt-home.demon.co.uk

The contents of     | Pickle's Law:

this message are    |   If Congress must do a painful thing,

purely my opinion.  |   the thing must be done in an odd-number year.

Don't believe a     |

word.               |