As the drive continues to reduce the size of Printed Wiring Assemblies (PWAs),
improve performance of electronic assemblies, and reduce costs of these products,
reliable secondary (bottom) side reflow operations must be developed. Attaching Surface
Mount Technology (SMT) components to the secondary side of a Printed Circuit Board
(PCB) is accomplished by placing components on the PCB's secondary side and
processing it through the reflow oven at this point. This board is then flipped over so that
more components can be placed on the side that is facing up (primary side). The PCB
must again be processed through the reflow oven. Large Integrated Circuit (IC) packages
that are soldered to the secondary side fall off of the PCB during reflow of the primary
side. Intuition may lead one to believe this is caused solely by weight, size, etc., but
experienced personnel are not able to consistently predict which components will fail.
The purpose of this work is to convey the necessary knowledge to explain and
predict the behavior of components during Secondary Side Reflow (SSR). This thesis will
ultimately present a method by which guidelines for SSR can be created.
Currently, SSR is limited to small passive devices and small Integrated Circuit
(IC) packages. It is anticipated that future PWA designs will require large ICs such as
Quad Flat Packs (QFP) and Ball Grid Arrays (BGA) on the secondary side. A large
variety of SMT components are available, but the focus of this research was directed
towards large IC packages. Current manufacturing guidelines for such products do not
exist and development of these are imperative if a costly trial and error approach is to be
avoided.
In an environment where product technology advancement and cost reduction are
key to survival, industry must develop and understand this manufacturing process. Cost
savings from SSR will be most directly realized with compressed product development
cycles, reduced use of PCBs, components, and raw materials, and more efficient use of
manufacturing capital and employees. These cost savings would be realized nearly
immediately after a set of manufacturing guidelines is developed. / Graduation date: 2000
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33272 |
| Date | 23 July 1999 |
| Creators | Yutzie, James D. |
| Contributors | Paul, Brian K. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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