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The purpose of this paper is to present the materials and process considerations and solutions that enable the safe use of plugging pastes in high density interconnection (HDI) printed circuit boards (PCBs) designed to operate at higher temperatures.

The paper introduces the concept of microvia plugging and the issues that are important in influencing HDI PCB reliability. Plugging pastes and their properties are discussed along with the various plugging processes that can be used. The advantages and disadvantages of each type of process are compared and contrasted.

The creation of via holes and the filling of these interconnection holes or buried vias and their subsequent copper plating is one of the key processes in HDI technology. In future, the importance of plugging will increase, particularly on account of the growing demand for copper plating and dimensional stability.

The paper highlights the importance of making the correct selection of materials and processing methodologies and details the implications of these choices.

The paper describes the different approaches that can be used for filling microvias and details the issues, advantages and disadvantages of the various approaches. The paper particularly focuses on the special demands on plugging pastes used in higher temperature range applications.

The paper aims to describe the various moisture loads affecting conformal coatings. It also seeks to differentiate these from dewing. In the case of dewing, osmotic processes may trigger completely different chemical‐physical processes on the electronic assemblies.

Numerous test methods are available to verify the climatic resistances of conformal coatings. Focussing on moisture load and dewing, the different types of load are discussed and illustrated by means of examples.

The tests performed to ascertain the temperature and moisture load of conformal coatings show that under these high loads the electrical functional reliability is maintained. Thus, impacts of the individual process steps can be examined and assessed by means of moisture and insulation measurements.

Utilising different stress evaluations the described tests demonstrate the qualities of conformal coatings for electrical assemblies. Prospective tests for the purpose of lacquer and process qualification are presented.

The physical‐chemical load types with their consequences on conformal coatings for the protection of electrical assemblies are described.