Conformal coating inspection is the key to success in production

Circuit board inspection of conformal coating is the most critical process in the complete production line.

Get this wrong and the reliability of the board can be significantly effected.

Inspection should be carried out on completion of the coating process. However, it is often a neglected stage of the conformal coating production line.

Conformal coating inspection reduced size
Conformal coating inspection is often a neglected stage of the conformal coating production line

 

 

The International standards such as IPC A 610 and IPC CC 830 are explicit in their requirements for conformal coating inspection. Yet, few companies actually inspect to the required level or indeed understand what is required.

Click to find out more about the conformal coating standards and also how you can improve your conformal coating inspection process.

Need help with your process?

Contact us at Nexus and we can help solve your issues.

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Nexus Series of Webinars: Conformal Coating Inspection and Quality of Coated Board Assemblies

Nexus are to hold a series of webinars on conformal coating topics in the Autumn of 2012.The series of four online conformal coating webinars will cover the following topics and each last 90 min. The third of the online training webinars will be:
Inspection & Quality of Coated Board Assemblies
Monday 7th January

Conformal Coating Inspection standards exist from a variety of sources and are based mostly on practical experience. There are many cosmetic defects that are reworked in industry which are unlikely to actually impact on product quality. The majority of coated products are inspected manually but with the growing use of coating application in high volume, automatic optical inspection is gaining in popularity.

Topics will include:

Inspection standards and what is important
Understanding some of the coating terminology
Manual & automated inspection
Common process defects & why they occur
Recording & charting defects in a process
Cosmetic process indicators

Please click online conformal coating webinars for further information.

Ask The Expert: Gordon Watson, Advanced Coating robotics, Conformal Coating Dip Systems on Key Conformal Coating Inspection Challenges

“When considering the finish of the circuit board and what the quality of the coating is like we find customers perceptions and ours can vary. This is generally down to preconceived ideas of what a good quality coating should look like.”

“The standards state that when dipped a PCB can have coating dripping at a corner and have bubbles within. However, many customers don’t like this. The problem is that to reduce the dripping effect tends to have a knock on affect on the rest of the quality of the PCB like conformal coating thickness. So, educating the customer on what they should be inspecting and what is acceptable is key for the conformal coating inspection process

Visit the Nexus Associate Experts Section and read what other experts have to say about conformal coating inspection.

Ask The Expert: Chris Palin Humiseal, Conformal Coating Materials on Key Conformal Coating Inspection Challenges

“The UV brightener used in conformal coatings can vary from different coating manufacturers. The variation is due to volume or type of brightener used. Generally speaking a high brightness UV tracer will  aid the automatic inspection system to identify that correct coating areas are covered and also look for stray material that may have entered critical keep out areas.”

“Some conformal coatings do not contain UV tracer and this is usually for a reason such as coating over LEDs or optical sensors where the UV tracer could affect light transmission. UV brighteners degrade over time with exposure to UV light therefore the coating on older PCBs may not show up quite as well depending on time and physical location of the board during its operational lifetime.”

Visit the Nexus Associate Experts Section and read what other experts have to say about conformal coating inspection.

Ask The Expert: Dr Joerg Schambach, Goepel, Conformal Coating Inspection Systems on Key Conformal Coating Inspection Challenges

“How can conformal coatings effectively and cost-efficiently be checked?”

“Applying conformal coating is the last step within the PCB production cycle. Similar to the previous production stages, quality assurance measures must be executed. After coating the assembly, proper wetting is mostly visibly checked by manual means. Because manual optical inspection has proven inappropriate for high PCB output, so called automated optical conformal coating inspection systems have been developed. They enable automatic testing of the correct wetting within the production line cycle.”

Visit the Nexus Associate Experts Section and read what other experts have to say about conformal coating inspection.

Ask The Expert: Dr Lee Hitchens, Nexus on Key Conformal Coating Inspection Challenges

“Considering the Key Inspection Challenges faced by users, then continuity of what people actually require in terms of quality of finish is the biggest problem for conformal coating inspection. Using the standards available are fine but many companies don’t really read them and actually don’t understand them fundamentally.”
“For instance, is it really okay to have debris on the surface of a conformal coated PCB? The IPC IPC-A610 Acceptance Standard states it is okay as long as the, “Foreign material does not violate minimum electrical clearance between components, lands or conductive surfaces”. I guess that most would not consider this okay cosmetically even if technically and electrically this is fine. This discrepancy in understanding is key to inspection”

Visit the Nexus Associate Experts Section and read what other experts have to say about conformal coating inspection.

Ask The Expert: Phil Kinner, PVA, Conformal Coating Robotic Solutions on Key Conformal Coating Inspection Challenges

“Many users are looking to automate their inspection process, in order to increase their quality level.  Systems are available that can integrate a camera and lighting, directly into a selective coating robot, or can be used in a standalone fashion separate machine.”

“There are numerous  challenges involved in automating the inspection process, not least of which is the variation in brightness of fluorescence of the conformal coating materials, both batch-to-batch variations and between different conformal coating materials.  Silicone materials in particular can have very low levels of fluorescence.”

“Other issues relate to the 3D nature of the substrate, light scattering leading to distortion of the images, background fluorescence of metallic solder joints/component leads and tall components or component bodies restricting the field of view, rendering it nearly impossible to inspect beneath or around through hole capacitors and connectors.”

Visit the Nexus Associate Experts Section and read what other experts have to say about conformal coating inspection.