A Study of ESD Corrugated - talkpkg.com

1 1A Study of ESD CorrugatedLarry Fromm, PERobert J. Vermillion, CPPC ertified, ESD Engineer-NARTEC ertified, ESD Engineer-NARTEC orporate EngineeringARP EngineeringHewlett-Packard CompanyPO Box 6481501 Page Mill RoadClayton, California 94517 Palo Alto, California 94304(925) 673-0225 Phone(650) 857-8948 Phone(925) 672-3316 Fax(650) 857-4646 Electrostatic Discharge (ESD) Corrugated protective packaging is evolving to the point where newtesting procedures need to be implemented in the evaluation process. This paper will serve as a general overviewin outlining some test methods aimed at the qualification process for ESD Corrugated and attempt to provide someunderstanding of what differentiates one ESD packaging product from another.

2 In the course of this paper, we willexplore mechanical, electrical and environmental considerations as we search for the "perfect package". This paperwill address some basic design considerations in conjunction with testing the ESD professional, the issue of appropriatepackaging seems to persist, day in and day out. In themidst of process and technology improvement, ESDcorrugated packaging is ripe with new technology andbetter ideas. Although initially, not particularly receivedby the ESD engineering community, ESD corrugatedpackaging has begun to foster acceptance and hasreceived widespread use in recent total cost reasons, the use of ESD corrugatedpackaging offers several attractive features and benefitswhile offering physical strength and electricalperformance over a long duration.

3 In addition, thesaving of labor and material by not having to use ESDbags has cleared the path for ESD paper the user community, expectations seem to varywidely for ESD protective properties. While someelectrical equipment manufacturers prefer corrugatedboxes that are essentially 'conductive', others have astrong preference for using 'dissipative' boxesexclusively. For the purpose of this paper, our ESDdesign goals included the usage of a buried shieldinglayer, a dissipative surface and low paper will explore mechanical, electrical andenvironmental considerations. Many coated andimpregnated products have been manufactured to insureESD protection, but may pose other hazards asconductive particle sloughing.

4 A method known as theSutherland Rub test will be reviewed as a tool in evaluatingthis problem. Air and spacing can contribute to theeffectiveness of protective packaging. Various flutestructures are available, including B, C, E or F flute. As Bflute is the most widely used structure for ESD Corrugated ,this structure was generally used for testing performed in the development of CDM safe technologies, staticdissipative surfaces and advancements in paper technologyhave opened the door for improvements in ESD paperproducts. Static dissipative technologies, including coatingswill be discussed along with their effectiveness for use in theelectronics will be discussed in depth and the various ESDcorrugated technologies will be evaluated for characteristicssuch as repulpability.

5 This paper will address some basicdesign considerations and testing procedures, including whathappens to paper in low relative Paper DefinitionsKraft is of German origin meaning strength, whichdesignates pulp, paper or paperboard produced from woodfibers by the sulfate process. One type is cylinder Kraftcontainerboard, which is a multi-ply formation withpredominate grain direction of fibers made from a naturallight brown like Kraft pulp on a cylinder machine. This typeof paper making technology is widely used. Corrugated is thecorrect term for "cardboard" box liner(s) and medium thathas been bonded together by a corrugator. Fiberboard is a2general term describing combined paperboard( Corrugated or solid fiber) used to manufacture sheets orcontainers.

6 It can take two or more paperboard linersand is adhered to a fluted Corrugated medium to formcorrugation or a makeup of two or more paperboardliners. Through lamination, solid fiber or a foldingcarton material will form boxes. Paperboard includesthe broad classification of materials made of cellulosefibers, primary and recycled wood pulp, recycled paperstock, newsprint, packaging papers, solid and chipboardfibers that can be made into boxboard, chip board, solidfiber or fiberboard. Containerboard is the paperboardcomponent (linerboard, Corrugated materials andchipboard) used to manufacture Corrugated and solidfiber. Medium is a paperboard material that has beenformed into a wave shape or flute structure and isusually buried between one or more is the paperboard used for the flat outerfacings of combined Corrugated fiberboard or laminatedas the outer facings of Crush Test (ECT), TAPPI-811, EdgewiseCompressive Strength of Corrugated Fiberboard (ShortColumn Test), was used for determining thecompression strength of Corrugated liner in lbs/inch.

7 Aspecial holder was employed to support precutcorrugated specimens in a vertical position to besubjected to a top load. The Scott Bond test TAPPIUM-403 measures the amount of force required to pullapart the upper and lower surfaces (liners) of aspecimen as adhered on both sides to a test Electrical Design CategoriesAdmittedly, the choice of design sets (or attributes) forcorrugated packaging is rather arbitrary. In the researchfor this paper, it was noted that there must be at least adozen or more approaches in industry use today, andnot all methods were evaluated. From a definitionstandpoint, all designs evaluated were "non-homogenous" ( "layered") arrangements.

8 Thefollowing criteria was based upon the methods used toaccomplish shielding and surface Design Category 1"Conductive InkCoating"In this approach for shielding, the design usesconductive ink coated onto Kraft near the surface(s).The surface is designed to have a dissipative sealant,which also reduces sloughing, and tribocharging(Illustration 1).llustration 1 Design Category 2 "Buried Metal In this approach, for shielding, the design uses a metal filmwhich is buried close to the flutes and a polymer film whichis dissipative on the surface (Illustration 2).Illustration 2 Design Category 3 "Buried Conductive Ink" In this approach, for shielding, the design uses a printed,conductive ink onto the liner in close proximity to the flutes,or the flutes themselves are conductive by virtue of carbonblack impregnation.

9 The dissipative surface is accomplishedvia dissipative ink printed onto the surface, with or without adissipative varnish (Illustration 3).Illustration 3 Design Category 4 "Buried Carbon BlackImpregnation"In this approach, for shielding, the design uses a buried,carbon black to impregnate the inside liner layer, closer tothe flutes than to the surface. The dissipative surface is3accomplished by using progressively lighter amounts ofcarbon as the top surface is approached. Generally, apolymer coating is : As a control , or reference, aluminum foil or plainKraft Corrugated material was employed for comparisonpurposes to all four-design categories (Illustration 4).

10 Illustration 4 Although Corrugated natural Kraft ( Corrugated orcardboard) boxes were found to be static dissipative athigher relative humidities, the Kraft paper was notelectrically conductive enough to provide the desiredstatic shielding. Kraft paper is hygroscopic (absorbswater), and the porosity of the surface can make paperbecome dry at low relative humidity [below 23% to30% for bleached white and below 12% to 15% relativehumidity for Kraft paper]; thus, the material s resistancetends toward the insulative range. It has a tendency notto drain a charge effectively, nor prevent a charge frombeing Electrical Surface Resistance Versus RelativeHumidity (RH)Fundamental to electrical measurement is first effort to characterize the various designs wasto measure surface resistance.