Bernard and Jim,
Here is my approach to Solder Stencil design. Feel free to use it if
the results please you too. You can also have a spreadsheet program
that I've developed to simplify the stencil design process - its in
Microsoft Excel format. If you are interested, contact me directly and
I'll E-Mail it to you. BTW, you can get additional information on
stencil design, and many other topics of interest by doing a keyword
search at the IPC E-Mail Forum for DesignerCouncil
http://jefry.ipc.org/archives/designercouncil.html and TechNet
http://jefry.ipc.org/archives/technet.html . Enjoy !
Solder Volumes:
Toe = average Terminal Width x 0.5 x average Terminal Thickness x (
average Terminal Thickness + 1.5 mils)
Sole = the lesser of ( average Terminal Width and ( Design Pad Width -
Etch Factor )) x average Terminal Length x 1.5 mils
Inner Heel = average Terminal Width x 0.215 x 2 x average Terminal
Thickness x 2 x average Terminal Thickness
Outer Heel = average Terminal Width x 0.5 x 2 x average Terminal
Thickness x ( 2 x average Terminal Thickness + 1.5 mils )
Sides = average Terminal Length x 2 x 0.5 x absolute value of ( average
Terminal Width - Design Pad Width - Etch Factor ) x 1.5 mils
Aperture Dimensions:
Aperture Width = Design Pad Width - ( Etch Factor/2 if Design Pad Width
< = 12 mils, otherwise Etch Factor/1 )
Aperture Length = ( Paste Volume/Solder Volume ) x ( 1/( (Stencil
Thickness + 1 mil ) x Aperture Width )) x ( Toe + Sole + Inner Heel +
Outer Heel + Sides )
Paste Volume/Solder Volume = 2.00 for 90% metal, 2.57 for 85% metal,
3.60 for 80% metal, 4.50 for 75% metal
John Balchunas
IPC Designer Council Member
Southern New England Chapter
> Date: Wed, 20 May 1998 11:36:22 -0400
> Reply-To: "DesignerCouncil E-Mail Forum." <[log in to unmask]>,
> "Walton, Jim" <[log in to unmask]>
> Sender: DesignerCouncil <[log in to unmask]>
> From: "Walton, Jim" <[log in to unmask]>
> Subject: Re: Stencil Procedural Design
> X-To: "Bernard P. Domingo" <[log in to unmask]>
> Content-Type: text/plain
>
> Hello Bernard,
> I was curious to see how you are doing with the procedure. I am going to
> start one now also.
> Your Email has made me think that it is a good idea for my job too. I am
> not a process engineer I am a PCB designer. My idea is to take the
> gerber file that I create from my layout cad software and create a print
> for Incoming Quality inspectors to verify the stencil correct. But now I
> feel I need to understand and create a procedure so that the stencils
> are created consistently from board to board. Please email any
> suggestions or generic forms that I may use and as I develop mine I will
> copy you for any feedback. Maybe together we can get a good document.
>
> Jim Walton
> [log in to unmask]
> Automotive Group
>
> > -----Original Message-----
> > From: Bernard P. Domingo [SMTP:[log in to unmask]]
> > Sent: Monday, April 13, 1998 8:59 PM
> > To: [log in to unmask]
> > Subject: [DC] Stencil Procedural Design
> >
> > Dear Sir/Madam:
> > Greetings! My name is Bernard P. Domingo, SMT Process Engineer from
> > EAI in the Philippines. I've received your catalog and Iwant to thank
> > you for all that information. In line with this, I'm going to make a
> > Project about Stencil Procedural Design, which will be our Company
> > Standard regarding Stencil Design. This will touch matters regarding
> > correct aspect ratio, snap-off distance, and pad-to-apperture
> > measurements. this project has the objective of eliminating or
> > minimizing defects such as solder balls and splashes. Your help will
> > be very much appreciated. If you could send me some information
> > regarding Stencil Procedural Design.
> >
> > Hoping for your cooperation. Thank you very much and More Power!
> >
> > Bernard P. Domingo
> > E-mail: [log in to unmask]
>
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