The lead to hole ratio has to consider the methodology of component insertion and whether or not intrusive reflow or pin in hole technology will be used. Additionally one must also consider whether the process is a lead-free process or a leaded process.

All of these must be taken into consideration during the design of the product. Lead-Free solder does not wet the surfaces as easily as the tin/lead solder, therefore more heat, both in solder pot temperature and top side preheat, is necessary to allow the solder to flow up into the plated through hole.

Leo Lambert Vice President, Technical Director, EPTAC Corporation At EPTAC Corporation, Mr. Lambert oversees content of course offerings, IPC Certification programs and provides customers with expert consultation in electronics manufacturing, including RoHS/WEEE and lead free issues. Leo is also the IPC General Chairman for the Assembly/Joining Process Committee.

In a study on "Lead Free Intrusive Reflow," SMT Magazine Nov and Dec 2007, we found that a pin to hole ratio much less than .6 resulted in voiding.

Bill Coleman Vice President Technology, Photo Stencil For over 18 years, Dr. Coleman has been the vice president of technology for Photo Stencil, working closely with customers to understand their printing requirements. His efforts have resulted in several new stencil products.

For consideration of a good solder joint, you will need to consider the following.

Solder Finish,Component Lead Mass, Auto or Manual Insertion, Soldering Method (Wave/Paste-in-hole/Soldering Iron/Preheater), Thermal Vents in Artworkand Solder used.

Assuming you areWave solderingandhave a 63/37 Lead and HaSL finish, this would be a robust system. We have seen good solder joint with adiametrical differencegap of .007 - .015

When using RoHS solders, they don't wet and follow heat as well. Therefore we depend on capillary action more, and this requires the gap above to be minimal. We target a .005 Minand .010Diametric gap.

Rodney Miller Capital Equipment Operations Manager, Specialty Coating Systems Rodney is currently Operations manager at SCS coatings, Global Leader in Parylene and Liquid Coating equipment. Rodney applies his 20+ years of diverse manufacturing to the Equipment Business at SCS Coatings. We provide unique value added coating equipment solutions for our customers. Including conformal, spin and Parylene coating expertise.

Refer to the Industry Standard for Printed Board Design (IPC-2221). It specifies through hole component pads, holes, and hole to lead clearances.

Mitch DeCaire Sales Manager (Americas), Cogiscan, Inc. Mitch DeCaire, Sales Manager at Cogiscan, has served the electronics manufacturing industry since 1989. His prior experiences include process engineering, business development, and engineering management roles with Nortel Networks, Vansco Electronics, Universal Instruments and Siemens.