Proposed Changes to IPC/WHMA A-620 Test Section

The IPC/WHMA A-620 Standard "Requirements and Acceptance for Cable and Wire Harness Assemblies" is again being revised. Revision A was released in July of 2006. While it is difficult to predict the release date of the next revision we thought you might like to know about the revision recommendations that resulted in draft chanages for electrical test.

If you want to learn more about A-620 and how you can influence future changes, see the note at the bottom of this page.

The following three recommendations resulted in draft changes:

1. Lower voltage for Dielectric Withstand testing when assemblies have small clearances
   (close spacing between connector contacts)


2. Increased "maximum continuity resistance" for long wires in small wire gauges


3. Adding shields and "no connects" to high voltage tests if shorts can occur (DWV and IR)

The following note was added to table 19-4 (Dielectric Withstanding Voltage Test (DWV) Minimum Requirements) for Class 2 (1000VDC) and Class 3 (1500VDC) assemblies.
"Voltage Level is applicable when clearance distance tested is "greater than" .58 mm [0.019 in]. When clearance distances are "less than" .58 mm [0.019 in] an agreement between the user and manufacturer to de-rate these test levels would be expected."

This ends the expectation that the full voltage would be used regardless of the clearance between electrical contacts.

More information regarding this issue can be found in several of our past newsletter application notes. See links to the right.

2. Increased "maximum continuity resistance" for long wires in small wire gauges.

Table 19-2 (Continuity Test Minimum Requirements) was modified for Class 3 Maximum Resistance:

Currently reads: "2 ohms or 1 ohm plus the resistance of wire whichever is greater"
Proposed change: "2 ohms or 1 ohm plus the maximum specified resistance of wire whichever is greater"

The language has been often interpreted as 1 ohm over nominal wire resistance. This new language clarifies the need to consider high side tolerance of permitted resistance (typically 8%) that can cause assemblies to be rejected with in-spec wire.

We created a detailed calculator to help you determine practical test resistance specs. For more info click on links to the right

3. Adding shields and "no connects" to high voltage tests if shorts can occur (DWV and IR)

The following text was added to section 19.5.3 Electrical Text Methods - Dielectric Withstanding Test Voltage (DWV) and 19.5.4 Electrical Test Methods - Insulation Resistance (IR)

"On points to be tested, harnesses shall be tested for DWV[/IR] for all isolated continuity paths as defined in continuity tests. Conductive connector shells and unused contact positions shall be included where a risk of a short exists."

This language makes clear that you must test interconnected points and even points without connections if they have a risk of a short/defect.

To help you determine if you should be testing unused points and/or connector shells click on the link to our detailed application note to the right.

If you want to know more about A-620 or how to add your input to changes in A-620:

A-620 is an industry consensus document. This means that it was not created by a company or government. Instead, participants from this industry came together to create the document and then vote on the final draft before it was approved. The electrical and mechanical test criteria tables can be downloaded for free here:

The latest version of the A-620 can be purchased through WHMA or at IPC at their online store. .

Click here for A-620 Revision Committee web page:

Under "Drafts" you can download a copy of the current standard with redlined revisions as presently planned for the next release.
Under "Comments" you can download a list of issues resolved and unresolved for the next revision.
Under "Submit a comment" you can recommend a change to be included in the next A-620 revision.