IPC 6012-DA Revisions: The Approach to Cleanliness, Thickness, Inspection, and Wicking

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IPC’s Automotive Addendum task group was started in November 2014 and the first edition of IPC 6012-DA was released in April 2016. We are now working on the revised version, and expect a release in Q2 2018. As standards need to evolve, develop and follow the needs of the industry, this work is continuous. This column will address some of the challenges the group faces and some of the issues we want to avoid by revising IPC 6012-DA. The automotive industry is an industry with high-volume production; this needs to be considered when developing a standard further.

The First Challenge: Cleanliness

We have so far focused on four areas for improvement. One of these are the requirements and test methods for cleanliness in printed circuits. The test requirements for cleanliness or ionic contamination used today date to the ‘80s and don’t fill the demands for today’s printed circuits, as these consist of more advanced technology and requirements than in the ‘80s. However, new ways and equipment to test cleanliness have recently been developed. As soon as the methods have been thoroughly tested, they can be implemented as a demand in IPC 6012-DA. Close communication with the IPC task group for cleanliness and continuous monitoring of the development and progress is the way to move forward. However, the group have decided that the methods are so promising, that we will implement them in the revised addendum—as a recommendation, not a demand.

Changes with Industry 4.0

When the automotive industry embraced Industry 4.0 the demands for more complex and small-scale electronics increased. Smaller and more complex printed circuits naturally increase the need for cleanliness testing as well. The challenge is when the test methods are not equally developed and as advanced as the printed circuits. It’s like building a new kitchen but keeping the old and malfunctioning appliances. The methods were designed for process control, not for the qualification of a production lot, as many believe and expect them to do. In reality, we still don’t have a sufficient and fast test method to do a proper lot qualification.

Another issue that has recently been brought up in discussions with test laboratories and internally in the Automotive Addendum task group is the ability to test local areas. Today’s methods measure the cleanliness of the entire printed circuit and are not able to find and locate local contaminated areas. To control quality and reliability you need the ability to measure cleanliness in those critical areas. New tools will make this possible, and it is a priority for the task group to evaluate and qualify improved methods to check the cleanliness of a specific area.

In addition to new test methods, we are also discussing at what time in the production process we should do the testing. Performing a cleanliness test of your printed circuit before soldering may provide a result contaminated by natural substances from solder mask. We believe this will vary by solder mask curing and will be hard to control. A solution on how to avoid this could be to send the bare PCB through a reflow process and perform a test on this one, since reflow will give the PCB an additional cure. This theory has been supported by a test report provided by Bosch.

A Standard for Thickness

The second challenge we spend much time on these days is the thickness of solder mask. The industry currently operates with two standards: standard a and b, referring to application methods. The group has reached the conclusion that this is not optimal. We consider adding a demand for a specific thickness, suitable for all application methods—a demand that will meet the requirements and still be manufacturable.

Expect Better Inspection

Our third challenge and area of focus is the level of inspections and inspection methods on the finished board. IPC requires that the inspections are after certain AQL (acceptable quality limit) demands. Automotive production requires 100% visual inspection. With the volume in this industry, and with increased miniaturization, a 100% visual inspection by an operator is not practical. Implementation of automated visual inspection is under discussion in the task group and will be added to the standard as a recommendation.

How do we measure wicking?

The fourth challenge that has been addressed by the task group lately is wicking, and how this is measured. According to our experience, the parameters provided by IPC are at best confusing. IPC requires that wicking is measured from the drilled hole edge to the point where the wicking ends. This might result in a false result where you don’t measure the wicking itself. In the new and revised edition of the Automotive Addendum, we will be precise that the measurement should start and stop where the wicking starts and stops. Only then will the results be correct.

Standards for PCB production specifications need to be alive and kicking, facilitating a modern production that meets the demands of today, not the ones in the past. As chair and member in several task groups, I know how much work lays behind a standard. The whole idea with task groups is to work diligently towards an improvement, assuring that all needs and consequences are considered and monitoring the challenges from all stages of production.

We need to extract knowledge from production files and convert it into useful information to improve the standards so they match the demands not only from IPC, but also the industry.

With that in mind, I believe we also need a digital article specification that picks up requirements from all bits in the supply chain, but that is another topic.

Jan Pedersen is Senior Technical Advisor at Elmatica. This column was originally published as a blog on the Elmatica website and reprinted here with permission.

This article originally appeared in the February 2018 issue of PCB007 Magazine.



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