The backbone of circuit connections: a look at how wire harness and cable standards were developed by association partnerships.

The transition from cancelled military standards to industry-developed standards has been in progress for many years. As liaison to committees developing standards for assembly and joining, I've already encountered the next generation in our industry--a generation that doesn't have a clue what M2KA-MIL-STD-2000A was. Even when Class 3 military hardware companies were being strangled by those requirements, commercially available workmanship standards were being used.

Simple Beginnings

The issue with assembly and joining standards is the lack of understanding concerning how they were developed. A section of the industry moved forward to develop electronic manufacturing standards with participation encouraged from all users and suppliers. Associations, such as IPC (Northbrook, IL) and EIA (Arlington, VA), partnered when members felt it was a good move for the industry.

The cable and wire harness industry was also lacking support in establishing industry standards and developing replacements for cancelled federal standards. The IPC became aware of parallel standards development efforts by the Wire Harness Manufacturers Association (WHMA, Arlington Heights, IL) and approached the organization for a joint effort. The WHMA provided a base of members with experience in high-volume, commercial-use cable and wire harness manufacturing, but no standards developing experience. The IPC brought the two groups together to move forward.

Initially, the process was not an easy one--many small cable/wire companies did not embrace the concept of different classes of construction, different reliability drivers and the formalized process of putting labels, such as target, acceptable, process indicator and defect, on the work.

Reaching an agreement between Class 3 documentation oriented manufacturers and small companies with a "sell it" or "scrap it" mentality required much patience and understanding.

Getting Down to the Details

The next obstacle was reaching an agreement on what features standards would contain relating to acceptability, process, material and testing requirements. Often, it seemed as though members had established an outline-of-the-month club! The document identification number seemed to change nearly as often as the outlines. In fact, the committee was more than two years into the project when it was discovered that the proposed standard had the look and feel of IPC-A600, Acceptability of Printed Boards and IPC-A-610, Acceptability of Electronic Assemblies. Finally, the process was coming together, but, because no supporting requirement standards like IPC-6012 and IPC/EIA J-STD-001 existed, the new standard, IPC/WHMA-A620, had a modified title--Requirements and Acceptance of Cable and Wire Harness Assemblies.

A Finished Product

The new standard was released in January 2002, featuring 280 pages and over 500 full-color illustrations in 18 chapters. To assure the best possible visual representation of the requirements, many of the illustrations were developed using 3-D modeling software. Common terminology is established early and adhered to throughout the standard (Figure 1). Cutaway (Figure 2) and x-ray (Figure 3) are intermixed with actual photos (Figure 4) to help a reader's understanding.

[FIGURE 1-4 OMITTED]

Vernon Judy, Sr., president of Qualastat Electronics, Inc. (Gettysburg, PA) and spokesman for the WHMA A-620 development, says the standard is a living document and one that will invite industry-wide feedback for improvement and fine-tuning.

"This is not a design guide--it's an acceptability standard. Every copy includes a feedback form with encouragement to provide constructive comments for future revision," said Judy. He also related that the need for the standard has evolved rapidly as electronics makers have developed other standardized practices. Judy believes the standard will be accepted quickly by the industry.

Future Considerations

The voluntary standard will be certified by the American National Standards Institute (ANSI, Washington, D.C.), which means the standards organization has assured the development process was open and that fundamental steps were properly followed. Additionally, the certification shows that a balanced group of users, suppliers and a general group, including training, test and consulting companies, were involved in development and consensus process.

IPC has a series of acceptance documents in place, with at least two more to follow. A proposed IPC-A-630 standard would establish consensus on box build or the assembly of circuit boards, cabling and controls in a device's chassis and installation of the chassis in the final vehicle. The proposed IPC-A-640 standard, meanwhile, will provide optoelectronics assembly and acceptance criteria.

Assembly Standards Update

The following standards and guidelines have been published since December 2001:

* IPC-4101A, Specifications for Base Materials for Rigid and Multilayer Printed Boards, covers the requirements for base materials (laminate and prepreg) to be used primarily for rigid or multilayer printed boards for electrical and electronic circuits. The standard includes specification sheets for laminate and prepreg, separated by family, with cross-references to UL, ANSI and former military designations.

* IPC-4103, Specification for Base Materials for High Speed/High Frequency Applications, covers the requirements for high-speed/high-frequency laminate or bonding layers used primarily for the fabrication of rigid or multilayer printed boards for high-speed/high-frequency electrical and electronic circuits.

* IPC-6018A, Microwave End Product Board Inspection and Test, establishes requirements for qualification and performance of high-frequency (microwave) printed wiring boards. The standard addresses both end product inspection and test of microwave boards for microstrip, stripline, mixed dielectric and multilayer stripline applications.

* IPC-9261, In-Process DPMO and Estimated Yield for PWAs, defines standard methodologies for calculating detects per million opportunities (DPMO) metrics related to electronic printed board assembly processes. The standard is intended for use in measuring in-process assembly steps, rather than end product determination.

* IPC-9701, Performance Test Methods and Qualification Requirements for Surface Mount Solder Attachments, provides specific test methods used in the establishment of levels of performance and reliability for surface-mount solder attachments of electronic assemblies. In addition to an understanding of the physics of surface-mount solder joint failure, this document also provides an approximate means of relating the results from the performance test methods included to the reliability of solder attachments for the use in environments and conditions of electronic assemblies.

At APEX 2002, the status of numerous assembly standards changed. The following is a list of standards being balloted for industry acceptance:

* J-STD-002B Solderability Tests for Component Leads, Terminations, Lugs, Terminals and Wires

* J-STD-003A Solderability Tests for Printed Boards

* IPC-HDBK-830 Guideline for Design, Selection, & Application of Conformal Coatings

* J-STD-004A Requirements for Soldering Fluxes

* IPC HDBK-005 Soldering Pastes Handbook to support J-STD-005 Requirements for Soldering Pastes

* IPC-SA-61A Post Solder Semiaqueous Cleaning Handbook

* IPC-SMEMA-9851 Mechanical Equipment Interface Standard (revision of SMEMA 1.2)

Jack Crawford is director of assembly, standards and technology with IPC, Northbrook, IL; [phone]; e-mail: [e-mail]