26.06.2020Przemysław ProlejkoIPC standards are the most important and most commonly applied standards to the design process of printed circuits. Why are they applied? Because they enable manufacturers to provide security and reliability.
In the area of electronics manufacturing services there are three categories determining the quality of electronic circuits assembly. The first class of accuracy indicates the lowest quality, the third one the highest. The accuracy classes are defined by particular IPC norms, for instance, IPC-A-610 applies to surface mounting.
We distinguish three IPC classes for which characteristic products are indicated.
- IPC Class 1 – general electronic products (e.g. torches, toys),
- IPC Class 2– products of higher durability and reliability (e.g. laptops, food processors),
- IPC Class 3– electronic products of high reliability (e.g. medical equipment, militaria).
IPC Class 1
It is referred to as the ‘general electronics’ category that includes the devices with the lowest quality requirements. It is applied to the products whose expected life cycle is rather short (e.g. toys). The costs of manufacturing such products are, consequently, lower than in case of more complex production processes that require higher quality and are compliant with the IPC Class 2 and 3 norms.
IPC Class 2
The devices of the second class are those electronic products that are required to be efficient and their life cycle is usually up to several years. They are expected to be failproof, but their possible faults should not cause an emergency. Among those devices we can distinguish, for example, a television or a tablet. It is not difficult to notice that in this case the malfunction would be more annoying and severe than regarding the Class 1 equipment, but it would not be life-threatening (as it can be with the Class 3 devices).
When designing a product to be manufactured, it is necessary to determine to which class it will belong. Designing a solution for a Class 2 product requires a different specification than for a Class 3. As an interesting fact it can be mentioned that devices manufactured as Class 2 products fulfil a lot of requirements of the Class 3, but rarely all of them.
IPC Class 3
In this group we can find electronic products of high reliability. Due to their importance in the field, their specification is determined by strict guidelines.
Products that fulfil the requirements of the IPC Class 3 should contain electronic components which are highly reliable as those devices are expected to provide uninterrupted service. Among them we can distinguish devices used in medicine (such as a pacemaker or emergency wards devices) and army (e.g. radar), but also solutions applied in other fields. The requirements concerning reliability are the strictest in this case and, as a result, the Class 3 electronic circuits are of the highest quality. In fact, a lot of products that could be included in the Class 2 (mainly because of their function) are produced according to the higher standard. Why? Because the benefits resulting from the higher quality may outweigh the costs of possible service activities.
To conclude, the Class 1 electronics are the elements with shorter durability and reliability. The Class 2 electronic devices have longer life cycle and are of higher importance. Finally, the Class 3 electronics include the devices that are of critical importance and, by definition, must be failproof regardless the circumstances.
Differences between the IPC Classes 2 and 3
Companies providing electronics manufacturing services often decide to manufacture exclusively the Class 2 and 3 products as they require fulfilling higher standards. Hence, their production process are designed according to those extremely strict requirements.
How do we distinguish, then, between the IPC Class 2 and 3 in the field of electronic circuit boards manufacturing? The main difference is the accuracy of placement and soldering of SMT and THT components. The requirements concerning the purity of assembly are also higher regarding the IPC Class 3. In fact, all the aspects of and factors influencing manufacturing have to be defined at the design stage and comply with the IPC Class 3 standards. With the use of a proper software that combines designing, verification and production functions a whole project can be realised according to the IPC standards.
Which factors should be taken into consideration while opting for a particular IPC class?
The first matter is, of course, the final function of a product. In some fields of the market only the IPC Class 3 is taken into consideration. In other cases it is just more profitable to manufacture a piece of equipment according to the Class 3 standards, even though the IPC Class 2 ones would be enough.
When applying production processes for the IPC Class 3, the increase in the production costs resulting from additional tests and audits must be taken into consideration. The electronic products must be specifically designed for a given class, in accordance with a proper IPC norm regarding a given production phase, for example, for the surface mounting it is the norm IPC-A-610.
