|Ask the Experts|
July 8, 2020
Confused About IPC-A-610 Class 2 vs. Class 3
My company is confused about IPC-A-610 Class 2 and Class 3. Some believe that Class 3 is for aerospace and Class 2 is not. The Class or standard used in Aircraft is what the OEM will use in the design submitted to the FAA and has nothing to do with IPC-A-610. Where did this thinking come from?
|Expert Panel Responses|
The question is confusing at best.
The inspection category to be used to inspect the product must be defined in the contractual agreement with the customer. The IPC definition of Classes of product is based upon the functionality of the product itself and its functional operation criterion. The Class 3 criteria is not based upon the industry but the application of the product.
For a product to be defined as a Class 3 product it must be built according to the total IPC criteria which includes laminate selection,plating thickness, manufacturing processes, material qualifications, facilities arrangements and inspection criteria.
The design team needs to address all these issues to verify the product will be fabricated to the requirements of the defined class, which is why there is a major price difference between the various classes of products.I don't know the FAA requirements, but I'm fairly confident the proposal submitted must address the classes of product which are going to be built and the measurement or assessment techniques or program which will be used to verify the product goodness.
The environment in which the product will be used,must also be considered as this is the reliability segment of the design. The product must be designed for its operational uses and this is not quality of the solder joint but the design of the joint.
I hope this is useful and if more is needed please don't hesitate to contact me at your convenience.
Vice President, Technical Director
I agree that the classes in the IPC-A-610 (or the J-STD-001 document for that matter) are completely unrelated to whether a product is used in an aerospace application. I believe that the common misconception that "Class 3 is aerospace" is related to the fact that this is often true.
For the most part, the added costs of meeting Class 3 requirements are uneconomical for most commercial, and nearly all consumer applications.
There are certainly industrial and severe service applications that require Class 3,however. It is really the environment and reliability requirements, not the application, that drive the selection of the class.
IPC classes, with regard to the Assembly Standard 610 are used to standardize the acceptability levels of electronics. Class 1 being least stringent to Class 3 being most. The standard is a tool to establish level of quality and communicate quality acceptance criteria across industry.
The secondary purpose, for our facility, is to ensure we understood the cost and inspection needed to support customers... what might be a 'process indicator' to one customer, is a 'defect' to another. This level of control for this is best defined with IPC 610 Assembly Standardization.
This standard and it's level, applies to any industry. The specification is product specific,as are the many levels of Military, ANSI, FM and UL standards that all have their independent purpose for product liability.
The PCBA's used in FAA regulated product, will need to meet specific FAA assembly standard spending their use and are generally coupled with specific test and environmental standards. If the IPC 610 standard and class is identified,you now know the level of quality expected from manufacturing systems only. Test specifications, Material control and other systems, will need to be evaluated for quality assurance, I would recommend.
Some product/components are much more stringent than others, which would be pending their location and purpose in aircraft and/or support systems. For this reason, there is not single standard that would meet needs of all FAA electronic products. Each has it's own criteria.
Capital Equipment Operations Manager
Specialty Coating Systems
I can't explain where your company's thinking came from about the IPC-A-610 Classes. I can help explain more about the class structure so you can educate your colleagues.
The standards recognize that electrical and electronic assemblies are subject to classifications by intended end-item use. Three general end-product classes have been established to reflect differences in producibility, complexity,functional performance requirements, and verification (inspection/test)frequency.
The user (customer/designer) is responsible for defining the product class of each assembly being inspected. The product class should be stated in the procurement documentation package.
CLASS 1 General Electronic Products - Includes products suitable for applications where the major requirement is function of the completed assembly.
CLASS 2 Dedicated Service Electronic Products - Includes products where continued performance and extended life is required, and for which uninterrupted service is desired but not critical. Typically the end-use environment would not cause failures.
CLASS 3 High Performance/Harsh Environment Electronic Products - Includes products where continued high performance or performance-on-demand is critical,equipment downtime cannot be tolerated, end-use environment may be uncommonly harsh, and the equipment must function when required, such as life support or other critical systems.
An aircraft may have assemblies on board which are any one of the three classes.The flight controls would most likely be Class 3 since it is imperative that the fly-by-wire controls function every time, all the time, and may be exposed to extremes of temperature/vibration at altitude.
Inside the aircraft, the electronics for the entertainment system or the flight attendant call button may be a Class 2 or even a Class 1 assembly.
I wouldn't say that the design submitted to the FAA has nothing to do with the IPC-A-610. More correctly I would say that the design OEM submits to the FAA will specify to what Class the assembly should be inspected and then,when the assembly is manufactured, the inspection should be to the Class as specified.
Manager of Assembly Technology
I've seen multiple times the association between Class 3 electronic products and aerospace applications.Usually, the space applications are expecting higher level of quality. However,there are devices that take off and others that stay on the ground and they serve the same industry and/or application.
The final requirement is going to be made by the customer through their purchase order, statement of work,drawings, etc. The customer requirement will supersede any other IPC requirements so there should be no confusion.
Engineering and Operations Management
There should be a Contract Letter between your company and the customer. The Contract Letter or the Statement of Work (SOW) typically referenced in the Contract Letter defines the general standards the product will be fully compliant with. For Class 1 and 2 PWBs, finished CCAs, or final products, simple compliance to J-STD-001 and/or IPC-A-610 is often all that is required.
For high-reliability applications (not just avionics, but also medical, industrial, aerospace, avionics, and military and many other applications, Class 3 is generally the DEFAULT criteria; they often have a custom Technical Data Package covering all build requirements that are exceptions (over and above or different)from J-STD-001, including many Ordnance Directives, Mil-STDs, medical standards, etc.
But to answer your question, yes it is possible that the bare PWB built to Class 2 will meet all of the requirements from the PWB perspective, but the finished assembly may require certain quality levels in Class 3, or above Class 3, as defined in the custom requirements. High Reliability requirements can be assigned to many different industries, not just Aerospace.
Examples would be medical devices, both intrusive (think pacemakers) and non-intrusive (CT scan), train controls, tank mission computers, down-hole drilling applications (nobody's life depends on it, but extreme high reliability is still required for functionality), and so on and so forth.
IPC-610-A is for the inspection and acceptability of printed circuit boards and assembly's. The class of product is decided between customer and supplier.Michael Eccleston, Integrated Technologies
The order of precedence contains that decision, the master drawing and at the bottom , IPC-610-A. If a product requires high spec and high reliability, class 3 would be advised. It would be pointless and uneconomical to call for a tv remote being built to be inspected to anything above class 1.
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