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The purpose of this paper is to present a detailed overview of the current stencil printing process for microelectronic packaging.

This paper gives a thorough review of stencil printing for electronic packaging including the current state of the art.

This article explains the different stencil technologies and printing materials. It then examines the various factors that determine the outcome of a successful printing process, including printing parameters, materials, apparatus and squeegees. Relevant technical innovations in the art of stencil printing for microelectronics packaging are examined as each part of the printing process is explained.

Stencil printing is currently the cheapest and highest throughput technique to create the mechanical and electrically conductive connections between substrates, bare die, packaged chips and discrete components. As a result, this process is used extensively in the electronic packaging industry and therefore such a review paper should be of interest to a large selection of the electronics interconnect and assembly community.

SMT adhesives are applied to printed circuit boards by the following techniques: dispensing (c. 90% of all manufacturers use this technique at present), printing and pin transfer. The conventional dispensing method of applying adhesive utilises variations in dispense time, pressure and temperature combined with needle diameter to form deposits of varying volume and geometry. Recently, the printing technique has attracted a lot of interest. This technique is well known from solder paste printing. The major driving force is the higher throughput of this application method. moreover, a new printing technique with thick stencils allows the deposition of glue dots with different diameters and different heights. Two printing methods will be discussed: conventional printing technology and printing with thicker stencils.

ISHM‐Benelux has recently set up a permanent secretariat at the following address:

The general section of the paper discusses in detail the demands of SMD‐Technology on Printed Circuit Boards, namely dimensional, thermal, electrical and chemical requirements on both substrates and finished PCBs, besides characteristic features of the production process and the overall performance of the assembly. The second part is concerned with a survey of materials and methods suitable for the needs of SMT printed circuitry. Emphasis is laid on appropriate substrates, thermal management of assemblies and PCBs for high speed/high frequency applications

The objectives of this research are to model the screening process with planned experiments and to identify the optimal setting of the process parameters so as to minimize the printing defects. The percentage volume matching (PVM) and defects per unit (DPU) are the two quality characteristics of interest. A fractional factorial design was employed to study simultaneously the effects of eight process factors on the PVM and DPU and their possible interactions. Subsequent analysis shows that a low level of the stencil cleaning interval and low temperature results in the minimum DPU while maintaining a PVM very close to 100 per cent. Empirical relationships between these two quality characteristics and the important factors were formulated using regression analysis and close matches were found during subsequent validation experiments.

Little interest has been shown in pickup conditions and parameters and their effect on placement accuracy in the literature before. The purpose of this paper is to find out the possible link between pickup conditions and placement accuracy of typical discrete chip components.

A dedicated test board was developed and used to study the ultimate critical pickup conditions. Then the same board was used to find out the best parameters between ultimate conditions and perfect conditions in order to define working limits for good enough pickup that would work well in practice.

The link between pickup conditions and placement quality was found and converted into measurable controllable values. Additionally, a problem was surprisingly detected in the placement machine's vision performance resulting in inaccuracy, and parameters were re‐defined to avoid this problem in real‐world production. Based on all the findings, the best parameters were defined for component pickup.

This paper discusses the effect of component pickup conditions on accuracy which is seldom handled in the literature. Owing to smaller spacing between chip components in the future, pickup is becoming more important; components will simply have to be picked up more and more on the centre to avoid collision with components already been placed. This paper clearly shows the requirement for placement machine manufacturers to develop more accurate pickup tools for the future.