Neptune Packaging System

Problem Statement:

The Neptune chassis design can realize a fabrication cost savings using a pre-plated CRS raw material vs using CRS with a zinc plate and chromate finish.  The issue with the pre-plate material is that the punched/exposed edges are susceptible to rust and corrosion.  It is deemed unacceptable for a customer opening his shipping container and removing a new chassis to find visible rust and corrosion on new product.  Therefore a solution to protect the unit during transportation and storage to humid climates was investigated.

Proposals:

Product packaging will follow a traditional path of packing foam to protect the unit from shock and vibration with an outer corrugated paper carton to contain and protect the unit in transit.  A plastic bag is also typical to protect the unit from gross moisture exposure, ESD, and to avoid chaffing of the foam packing against the chassis surface while in transit.  The proposed solution to the rust and corrosion concern lies in the choice the plastic bag; two specific products are offered by packaging industry.

A major VCI manufacturer offers a static and corrosion protection system that was specifically tailored to the Neptune chassis characteristics. A major VCI manufacturer’s product is called VCI. This system consists of a Poly bag that has a chemical coating applied to the inner surface of the bag that constantly out gasses during it’s life.  This gas is meant to fill the bag and attach itself to all the surfaces of the chassis.  This gas acts as a barrier to prohibit waterborne oxidants and other corrosives to attack the exposed steel surfaces hence eliminating the rust and corrosion.  The tailoring that was performed by a major VCI manufacturer for Neptune basically entailed calculating the volume of the chassis and the shelf life/storage period desired which drives that amount of gas or the coating chemical that will be needed on the bag.  In the case of the Neptune chassis a bag as well as 2 strips of 1¼”foam containing additional chemical will provide a shelf life of 6 months.

Liberty Packaging offers a different static and corrosion protection system. Liberty’s product is called Static & Corrosion Intercept. Their system consists of a Poly material that is chemically impregnated with a copper semi conductor material.  The copper material acts as a sacrificial element that absorbs the corrosive forces protecting the chassis from rust and corrosion.   This system works with the bag alone; no other elements are required.  The shelf life for Neptune chassis packaged in this bag is estimated at several years based on the size of the bag needed to fully cover the unit and subsequently the content of semiconductor material contained in the bag formulation.  Liberty Packaging is a distributor for Engineered Materials, Inc.

Selection Process:

Both a major VCI manufacturer’s product and Liberty’s product were tested in a humidity chamber by 3Com.  3Com tests were conducted in Bell Labs in Burlington, MA.  The test consisted of 9 days @140°F at 90-100% relative humidity.  The samples tested were a 12”x12” panels of perforated pre-plated sheet metal.  The samples were bagged in a standard Poly bag, the VCI bag, and the Intercept bag.  The results were as follows:

Poly Bag:             All samples rusted in many locations including the raw edges.  The samples were wet as a result of the testing.

VCI bag:              Some areas showed more rust and corrosion than others.  But all had noticeable residue.  The samples were also wet as a result of the testing.

Intercept bag:            These samples exhibited only extremely minor signs of residue.  The galvaneal material showed the least amount of residue.  This residue was red rust that would be viewable under a magnifying glass along approx. 0.1” of one edge.  None of the samples were wet as a result of the test.     

History:

a major VCI manufacturer Corp. also conducted tests using 3Com’s 12”x12” sheet metal samples in their own labs.  The test followed the ASTM G85 test procedure.   In short, this procedure exposes the samples to a fog spray at a temperature of 120°F over a 9-day period. The results were as follows:

Unprotected samples:             All samples rusted in many locations including the raw edges after one day of exposure.

Poly Bag:                      All samples rusted in many locations including the raw edges after four days of exposure. 

VCI bag:                        No corrosion was exhibited after nine days. (This system does not support the Neptune needs alone.  VCI foam is also needed to accommodate the size and volume.)

VCI bag with VCI Foam:         One sample exhibited slight corrosion along one edge after nine days of testing.

Other factors influencing the selection process were number of components needed to support the solution.  More components equate to added labor at pack out as well as material ordering, stocking and handling.  The Intercept solution is comprised of a bag.  This would be in place of the more traditional Poly bag.  The VCI solution is comprised of a bag and 2 foam strips.  Material cost is another factor. The VCI bag solution dictates sealing the bag closed in order to capture the gaseous environment created within the bag to provide the protection.  While hermetically sealing the bag was ruled out as too difficult to make part of the pack out process, tape sealing the VCI bag would perform for the 6-month life.  Tears or major punctures to the bag while in use would degrade the effectiveness of the VCI solution thereby reducing the storage life for the chassis.  The Intercept bag does not degrade with time.  Openings in the bag do not reduce the effectiveness from an environmental perspective as long as the majority of the chassis is covered (does not need to be airtight /hermetically sealed; tape sealing is sufficient).  Below is a table outlining these factors:

Recommendation:

While the Intercept solution costs slightly more than the VCI solution, all the other selection factors point to the Intercept product as a more robust solution.  The 3Com test samples clearly show a cleaner better-protected product at the outcome of the testing.  The protection against moisture and corrosion was superior.  Dealing with only a bag in the pack out process offers a relief in handling and material logistics vs the VCI bag and foam solution.  With a recent experience where the E16 chassis was packed out at with a process check list inadvertently included in the module bay area of the chassis, (which would have caused lots of noise and other havoc had our customer powered up the unit), eliminating the need for 2 foam strips would avoid a similar situation.  The need or lack of need to tightly seal the bag along with the increased protection life also makes the Intercept product stand out as compared to the VCI product.

The Liberty Static & Corrosion Intercept bag is the recommended solution for the Neptune chassis fabricated in a preplated zinc sheet metal.  Intercept product should be procured in order to support the pilot build.  These units will be distributed to various parts of the world using traditional shippers.  This would be an opportunity to try the Intercept product in action on real units under real conditions.