Original Date: 07/25/2005
Revision Date: 09/12/2006
Information : Vacuum Bonding Process
Northrop Grumman Electronic Systems improved the processing of surface mount assemblies using a vacuum bonding process. This approach resulted in improved versatility and consistency while providing high first-pass yield. Innovative use of masking material allowed Northrop Grumman Electronic Systems to use adhesives with superior thermal and electrical properties. Northrop Grumman Electronic Systems is sharing its knowledge of vacuum bonding of surface mount assemblies with its sub-tier suppliers to enhance quality and consistency of material provided by these suppliers.
Northrop Grumman Electronic Systems’ (NGES’) manufacturing capabilities include the production of surface mount assemblies. In most cases, the assemblies produced are double-sided, requiring specialized springs, clamps and/or weights to secure the electronic components to the printed wiring board during processing. These production aids require customization for each assembly’s geometry and experience non-uniform temperature effects during heating associated with processing the film adhesives used to fix components to the board. NGES moved from this manufacturing approach to a vacuum bonding process that has proved to be more advantageous than the previously used approach. Vacuum bonding uses a bladder bag with a pulled vacuum to apply pressure to components as they are heated to activate the adhesive. The versatility of this process allows for consistent bonding of a variety of assemblies independent of geometry, permitting pressure adjustments to be made during processing for improved performance. More than 15 years experience with vacuum bonding has allowed NGES to become one of the first manufacturers to embrace vacuum bonding as part of a comprehensive surface mount process flow. NGES has shared this knowledge with several second-tier suppliers to improve the quality and cost-effectiveness of material provided by these suppliers.
Important aspects of this process that position NGES as a leader in vacuum bonding of surface mount assemblies include rigorous process control, advanced masking techniques, and implementation of just-in-time adhesive pre-form acquisition to ensure quality and cost-effectiveness in the process. During the vacuum bonding process, computerized oven logs are maintained while rigorous leak checks and bag maintenance are performed. These steps ensure that a consistent, repeatable processing occurs that has resulted in exceptional yield of surface mount assemblies.
NGES has also developed an innovative application of UV-curing masks to control material flow and allow the use of high-flow adhesives with advanced thermal and electrical properties. Adhesive pre-form quality is maximized by purchasing pre-cut pre-forms to be delivered only when required, meeting emergent requirements through the use of a computer-controlled plotter that can cut individual pre-forms “on the fly” from drawings. Because this material has a fixed shelf life, the latter capability precludes the need to store large inventories of adhesive pre-forms without negatively impacting scheduling and flexibility.
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