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SMD - Solder Mask - Cream Stencil

amerdsp

Hello all,

   I know that the default solder mask and cream stencil openings are

the same size as the smd pad.  However, in some cases, (such as on page

85 of this datasheet:

http://focus.ti.com/lit/ds/symlink/msp430f2274.pdf) the solder mask is

greater than the pad and the cream stencil is smaller.

 

Can someone please explain why is it done that way and can the default

eagle settings be used or would it create a problem?

 

Thank you,

 

A

 

  • On Sat, 21 Mar 2009 07:04:07 +0100, Amer Abufadel <amer.abufadel@gmail.com> wrote:

     

    Hello all,

       I know that the default solder mask and cream stencil openings are 

    the same size as the smd pad.  However, in some cases, (such as on page 

    85 of this datasheet: 

    http://focus.ti.com/lit/ds/symlink/msp430f2274.pdf) the solder mask is 

    greater than the pad and the cream stencil is smaller.

     

    Can someone please explain why is it done that way and can the default 

    eagle settings be used or would it create a problem?

    The solder mask is slightly bigger to make sure it doesn't overlap the pad. This will help to make a contact between the pad on the PCB and the chip lead. The cream stencil is made slightly smaller than the pad so no solder paste will go in between the pads. This helps to prevent short circuits.

     

    Thank you,

     

    A

     

     

     

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