Solder paste standard emerges

IPC-7527, the first published standard that originated outside the U.S., provides guidance for solder paste.

Solder paste is a necessity for basically all printed circuit boards, but it's one of the most overlooked technologies in the electronics industry. IPC has completed the first standard that will help development teams improve the quality of their solder paste operations, which could bring significant improvements in quality and reliability.

IPC-7527, Requirements for Solder Paste Printing, covers the many aspects of solder paste, from initial placement on the board through tests after boards are ready to move forward on production lines. The standard will cover a large footprint.

"This document is useful for anyone who uses solder paste," said Kris Roberson, IPC's manager of assembly technology. "Before this came together, much of the awareness for solder was 'tribal knowledge' passed from one person to another. That can get to be like the telephone game, where two or three generations down the road the information has changed quite a bit."

The benefits go beyond the unchanging nature of the printed word. The new standard serves as a reference guide for equipment operators. They can now turn to a book when they have questions and can't find the company expert.

"It provides the operators with a standard that will help them make the right decisions when they face with issues in production, and no professionals or specialists are present," Steven Juel Hansen, cochairman of the Solder Paste Printing Task Group and production engineer at Vestas Control Systems A/S, based in Hammel, Denmark.

That Hansen is in Denmark is quite significant. IPC-7527 is the first published IPC standard that originated outside the United States.

"The Nordic group came up with the idea, created the standard and brought a nearly-completed document to IPC. They had done a thorough job. Once they brought it to us it took less than a year to move it to publication. That's pretty speedy given the time needed for public comment and responses, as well as for getting the document ready to publish," Roberson said.

Given IPC's expanding global strategy, it's unlikely that it will be the last. Roberson cites another first for the document, this one on the technical side.

"There are standards that tell what the completed assembly should look like, but this is the first one to tell us what the solder paste should look like," Roberson said. "When things are written down, they provide a common language that clearly specifies requirements. IPC-7527 tells you how far off centers can be before they're considered faulty. In the past, operators did whatever the companies decided to do."

He noted that IPC-7527 is designed to be a useful document for equipment operators and others who work with one of this industry's basic infrastructure elements, solder. Preventing problems with this electrical and mechanical technology can help improve the quality and reliability of many printed circuit boards.

"The standard does a nice job of bringing out common problems, like solder that has rooftops or saddle shapes instead of a nice brick form, and it provides solutions so those issues can be fixed," Roberson said.

When issues like saddles and rooftops arise, the old adage of a picture being worth 1,000 words comes into play. Committee members endorsed that simple saying, packing 50 photos into the 15-page standard.

Though it's fairly short, IPC-7527 addresses a broad range of technologies. It covers solder paste from the early stages through production and testing.

"This covers everything from basic squeegees to jet dispensers and needle dispensers to closed print heads. It also provides information on automated past inspection using either cameras or lasers," Roberson said.

For more information on the standard (already available in English and Danish), visit www.ipc.org/onlinestore.