Printing materials paste selection

Component Placement. The purpose of the component placement machine—also called the pick-and-place machine—is to select the proper component, orient it correctly, and then place it on the circuit board, all with degrees of accuracy and precision that minimize defects on the finished product. In addition, the component must be placed on the printed solder paste, the dispensed adhesive, or a combination of the two deposits with a controlled pressure or release distance that does not excessively spread out either material or damages the component package. Moreover, the placement machine must execute these tasks as quickly as possible in order to maximize the production volume. Lastly, the equipment must be sufficiently versatile to address continually changing electronic packages, specifically dimensions and I/O configurations. 

Metal-Bumped Flip Chip Joints. ICAs can also be used to form electrical interconnections with chips that have metal bumps. ICA materials utilize much high filler loading than ACAs to provide electrical conduction isotropically (ie in all directions) throughout the material. In order for these materials to be used for flip chip applications, they must be selectively applied to only those areas that are to be electrically interconnected. Also, the materials are not to spread during placement or curing to avoid creating electrical shorts between circuit features. Screen or stencil printing is most commonly used to precisely deposit the ICA pastes. However, to satisfy the scale and accuracy required for flip chip... 

In the solder paste printing process, defects typically are caused by poor alignment between the substrate and stencil, incorrect material selection (substrate, paste type and stencil design), or variations in the amount of paste deposited. Defect elimination relies on the engineer and operator to address these variables and monitor the process. 

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