NEPCON West - Fiberoptic Expo Conference Proceedings


INJECTION MOLDED SURFACE MOUNT 32 PIN VISION PACKAGE COMPETES WITH CERAMICS

Authors: Wayne Louie, N. Li, T. Shaffer and R. Ross
Company: RJR Polymers, Inc.
Date Published: 12/3/2002   Conference: NEPCON West - Fiberoptic Expo


Seika Machinery, Inc.

Abstract: Why not make and process vision packages in a leadframe format using high performance thermoplastic molding alloys which take advantage of materials and process developments, which have been underway in aircraft, space, military and automotive industries for more than a decade? Compared to transfer molding compounds or ceramics, the thermoplastic counterparts have higher temperature resistance, do not outgas, have no ionic contamination, process much, much faster and can be easily made in a leadframe format leading to higher speed and substantially better processing economics.

If one looks at the above statements it seems to claim that an injection molded vision package would compete with the thermal characteristics of ceramic. Not so. However, vision packages must have a window affixed, and typically this is done with an epoxy sealant. The package is only as good as its weakest link.

Injection molding is fast and efficient, and is easily done in multi-up, leadframe format. What’s more, there is very little material scrap. Molding runners, etc. can be re-ground and recycled so the material utilization is well over 90%. This is another economic advantage.

Here is a partial list of items that will be covered in this presentation:
1. Packages weigh about half as much as the ceramic equivalent.
2. Flatness and dimensional tolerances compete head to head with either ceramic or transfer molded counterparts.
3. All of the processing steps can be easily automated because of the leadframe format, even to the extent of production on a reel to reel basis.
4. Electrical properties of the thermoplastics out-perform both ceramic and transfer molding materials, especially dielectric properties.
5. RJR Polymers has a proven method to individually seal lead penetrations permitting the sealed package to meet JEDEC standards - they don’t leak.
6. Tooling is faster and less costly to build. With a cycle time of less than 20 seconds (no post baking required for cure), throughput is very high. A single press, fully automated, can produce more than 50K sites per shift, depending upon the part size.
7. Whether a blue package, or a green package, or a red package is desired - it can be accomplished with thermoplastic compounds.

What has been learned in the 6 years of research and development leading to the availability of this package is that there is not just one single secret ingredient that leads to success. The program involves the most up to date molding equipment, design and construction of tooling in house, development of a patented, inverted stamping process to keep the penetrating leads from leaking, and this included the moisture barrier materials as well. Working with outside vendors was tried, but it just didn’t work. Ultimately everything was done in house, except for etching the leadframes and plating.

This paper will cover the items mentioned and discuss design, construction and performance testing, with supporting data.

Key words: injection molding, thermoplastic, alloy, adhesives, process.



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