See attached.

 

Dwayne Dunn

Sr. Process Engineer

Nextek, Inc.

201 Next Technology Drive

Madison, AL 35758

(256) 772-1995 ext. 1053

 

http://www.nextekinc.com/

 

-----Original Message-----
From: Bev Christian [mailto:[log in to unmask]]
Sent: Wednesday, April 10, 2002 7:46 AM
To: [log in to unmask]
Subject: Re: [TN] 0402 tombstone problem

 

Peter,

So which is worse - high tin (e.g. Sn/Pb95/5) or relatively "high" lead (Sn/Pb63/37)?

Bev Christian

Research in Motion

-----Original Message-----
From: Peter Lee [mailto:[log in to unmask]]
Sent: April 10, 2002 12:07 AM
To: [log in to unmask]
Subject: Re: [TN] 0402 tombstone problem

Our experience with eliminating 0402 tombstoning was to try different no-clean solder paste. We've also found that the parts' end termination tin/lead % has some negative impact on the yield.

 

Rgds,

Peter

 

 

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: April 9, 2002 8:13 PM
To: [log in to unmask]
Subject: Re: [TN] 0402 tombstone problem

 

I just heard something not too long ago, that round pads for 0402's are the way to go.

Never heard of that before, but just recently received a board for quote that uses round pads for the 0402 components...anybody else ever heard of this?

Guess I'll find out how it works inna little while, while pondering why a round pad would work better than a square pad....

-Steve Gregory-

Edward,

When we do everything correct on 0402 and 0201 and still have components
standing-up, we often look to the component terminations and find poor
plating.

Good luck
Dave Fish

----- Original Message -----
From: "Edward S. Wheeler" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, April 09, 2002 10:59 AM
Subject: [TN] 0402 tombstone problem


> Hi folks, we are running a new board with 0402 parts on it. It seems that
> we are having a tombstone problem as well as a problem with parts not
> staying centered on the pads. We are currently using 20 mil square pads on
> the board, with 20 mils of spacing between them. Our stencil is 6 mils
> thick, laser cut and electro polished. The trapezoidal walled apertures
are
> slightly reduced, 17 mils square, and centered on the pads. It appears the
> chip shooter is placing the parts perfectly. We are using eutectic solder
> paste with an OA flux, and reflowing the parts using the recommended
profile.
>
> Are there any suggestions any of you might have concerning this size of a
> part? Is there a better stencil design, reflow profile, or pad design that
> could help us out? I would appreciate any suggestions.
>
> Thanks.
>
> Ed