SMTA International Conference Proceedings

High Density Assembly In PCB Cavities

Authors: Jonas Sjoberg, Ranilo Aranda, David Geiger and Murad Kurwa
Company: Flextronics Advanced Engineering Group
Date Published: 10/13/2013   Conference: SMTA International

Abstract: Miniaturization and the integration of a growing number of functions in consumer products such as smartphones and tablets require an extreme high packaging density in x, y and Z direction and it is key to have a so called “tool box” of technologies to give designers as many options as possible.

One way to increase the packaging density is to reduce the size of the component, stack them on top of each other in a package or with Package on Package (PoP) and at the same time decrease the spacing between components.

Stacking parts on top of each other saves area but increases thickness and this is one of the key considerations for today’s consumer products and using the inner layers of the PCB for component placement could in some cases be an option to reduce thickness in localized areas of the assembly.

Using 01005, fine pitch CSP and PoP component’s, equal and below 0.4mm pitch, poses a number of challenges for PCB Design, SMT Assembly process and Reliability when using a standard PCB process and the challenge becomes even greater when mounting these parts in cavities of the PCB.

A feasible assembly process must be developed considering the full tolerance window for incoming materials such as PCB, components and tooling. The assembly process ranges all the way from screen-printing, dipping in flux or paste, reflow soldering in air or nitrogen.

Many factors influence the quality of the assembly process in cavities and the process capabilities for both assembly and PCB fabrication will be tested to its limit and beyond.

This paper will discuss different design & layout alternatives and assembly alternatives for high density assembly in PCB cavities and the challenges to do this with high and sustainable yields.

Key Words: 

CSP-Chip-Scale Packaging, TMV-Through Mold Via, PoP-Package on Package. 01005, miniaturized and cavity assembly.

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