I do not have any reliability study but 6 or more years ago I was loading a Dell work station mother board when I was working at a contract manuacturer and first experienced oval, "race track shaped" land pads on most all their passive parts. The smallest passive part in this case was 0603 sized. I understand that Dell did research on this subject and from that came out with this design. The logic is there for both lead and lead-free designs to have the rounded corners. If you look at a solder fillet around a passive resistor for instance which has a rectangular end and you will see that it is shaped like a oblong racetrack. You will have 360 degrees of fillet provided that the spacing between the land pads is such that the part overlap allows it. Virtually 100% of solder strength here is in the solder fillet. So, the most economical shape which uses the least amount of solder (reducing and amount of lead pollution) for virtually 100% of the solder stength is the rounded corner design. Dell also did the same for it IC's whose pitch was greater than 20 mils. It makes it easier for stencil design. I found it excellent for no-clean paste smt processes as it reduced or eliminated many of the reasons/opportunites for solderballs. You reduce all the apertures 1-4 mils (depending on the part/pad)or so and misprinting is not so problematic and solder wetting pulls 100% of the solder into the fillet as it remelts since there are no corners of solder beyond its reach. Not very scientific but that is my experience. I do not recommend this layout for passive parts that will be exposed directly to solderwave but I do not recommend that any SMD parts go through solderwave. You will have a hard time getting PCB layout people to do this but it is worth it. Dorothy Lush Manufacturing Manager i2 Telecom International, Inc. -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Lee Whiteman Sent: Wednesday, March 24, 2004 10:48 AM To: [log in to unmask] Subject: Re: [TN] FW: Round SMT pads Has anyone seen any reliability data to show that Lead Free solders would work better with rounded pads than with squared pads? This is not to dispute Brian's contention (I actually agree with him). I was just curious to see if any data supports this claim. Lee Whiteman Senior Manufacturing Engineer American Competitiveness Institute E-Mail: [log in to unmask] Ph: (610) 362-1200 x208 Fax: (610) 362-1290 This message is for informational purposes only and does not supersede, modify, or create any agreements with ACI. Information contained in this message does not bind ACI or its affiliates to any commitment, either express or implied, unless ratified in writing by an authorized representative. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian J. Toleno, Ph.D. Sent: Wednesday, March 24, 2004 1:29 PM To: [log in to unmask] Subject: Re: [TN] FW: Round SMT pads Another reason for rounded pads is when using Pb-free solders, due to the increase in surface tension and wetting angle, people are moving to rounded pads so that they don't have exposed corners after reflow. Brian J. Toleno, Ph.D. Sr. Applications Chemist Loctite Electronics 15051 East Don Julian Rd Industry, CA 91746 Ph: 626-968-6511 x304 Cell: 626-215-0879 ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. 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