Updated Cable and Wire Harness standard simplifies use

IPC/WHMA-A-620B uses images and international standards to help users.

November 19, 2012

By Terry Costlow, IPC online editor

Many IPC standards are closely related to other IPC documents, so it’s important that they use the same approach to make it easier for those who use multiple documents to move from one to the next. This desire for compatibility is one of the factors behind a revision of IPC/WHMA-A-620, Requirements and Acceptance for Cable and Wire Harness Assemblies.

IPC/WHMA-A-620B which is now available in the IPC online store, , was updated in part to provide compatibility with other important assembly standards such as J-STD-001E Requirements for Soldered Electrical and Electronic Assemblies and IPC-A-610E, Acceptability of Electronic Assemblies. Simplifying the document and making it easier to use were equally important factors behind the revision.

“We added a lot of photos,” said T. John Laser, co-chairman of the IPC task group that developed the standard. “Some of them show the proper way to do something. Others show exaggerated defects so it’s very obvious what’s wrong.”

This high emphasis on visuals is evident throughout IPC/WHMA-A-620B, which was created with input from the Wire Harness Manufacturer’s Association (WHMA). There are now 684 full color illustrations; of which 125 are new or updated. Another important addition was made to add a section that follows the lead of J-STD-001.

“We added a section on flow down, requiring that companies flow the standard down to their subcontractors to assure all hardware is manufactured to the same guidelines,” Laser said.

The section on molding and potting underwent some of the most extensive changes. Originally written mostly for high reliability products, it now has a broader scope.

“Class 2 and 3 manufacturers provided a lot more information on molding than we had in the previous version,” said Laser, a manufacturing engineer at L-3 Communications. “With thanks to Rhonda Troutman at Actronix, Inc., we’ve added 31 illustrations to this important section, where we didn’t have illustrations before.”

The document was also revised to make it more user friendly for users with varying reliability requirements and markets in different regions. The original version only had one table for pull tests, using a military specification. The new version includes many global standards.

“We’ve added UL, SAE and IEC tables. Depending on their customer’s need, users can look at different sections and know they’re meeting industry or regional requirements,” Laser said.

The standard also provides help for users who are moving to smaller wires and connectors. “As people use smaller and smaller connectors, they’re going to need smaller wires,” Laser said. “Many people can get by with 22-24 gauge wires now, but more people are talking about 32 gauge, which has only seven wires. With only seven strands, you can’t afford to damage any of them. It’s very easy, when wires are being stripped, to damage one or two wires. Depending on whether the product is class 1, 2 or 3, the standard lets people know whether a damaged strand is a defect.”

IPC-A-620B is now available at www.ipc.org/620.

Other chapters with a lot of changes include:
5 – Crimped connectors, covering a wider range of contacts and lugs.
8 – Splicing, with photos and better drawings for additional crimped splices.
9 – Connectors, with important assembly updates.
11 – Measuring cables and wires.
13 – Coaxial and Biaxial cables, including conformable and semi-rigid terminations.
17 – Mechanical assembly.

The IPC technical training committee, headed by Debbie Wade of Advanced Rework Technology in England, has already established direction for update of the IPC-A-620 training and certification program, with roll-out expected by February 2013.