Circuits Assembly - November 2007 - (Page 45)

Cover Story is ≈ 10°C above the stated softening point of the high-impact polystyrene material used in comPLCC 68 0.949” x 0.150”/ Nitto-Denko/ 3 mercial reels. Figure 5 Daisy0.949”/ 3.81 MP-8000C chained 24.1 x 24.1 shows a 13" reel that was CTE dummies* placed vertically, resting *Amkor Corp. on its rims, in an oven at Table 2. Experimental Tapes and Reels 70°C for 24 hr. During Item Description Manufacturer Part No. baking, it deformed to the Carrier tape Static dissipative Advantek Inc. PLCC68-AC40-0P2 point where it could no tri-laminate polystyrene carrier longer support itself and Cover tape Anti-static Advantek Inc. AA375005NP fell to a horizontal posipolyester tion. Obviously, this was a cover-tape reel - deformation failure. Reel High impact Advantek Inc. RD33028SW Figure 6 shows a highpolyester reel and RD33016SW impact polystyrene reel that was axially supported and baked at 70°C for 24 hr. No significant warpage was seen in either 13" or 7" reels.8 • Process temperature control is vital to the success of the novel process. The novel oven temperature is held to 70°C ±0.1°. Figure 7 illustrates the “wetting” adhesive failure that resulted from baking tapes at 72°C. The adhesive migrated over the entire underFigure 7. Tape adhesive wetting failside of the cover tape.7 A key to achieving ure (courtesy Advantek Inc.). this rigidly controlled temperature is a radical vertical, low thermal mass cylindrical ing shrinkage of 1% to 1.2%, which should chamber design. not prevent easy extraction of a package.”6 • Purge gases. The experiments proved that • Adhesive bond strength between the cover and purge gases, CDA or nitrogen, were not carrier tapes. Excessive temperature can raise required. the strength of the adhesive between the ■ carrier and cover tape to a point where the chipshooter can’t easily pull the cover tape References free from the carrier tape. EIA-481C specifies the peel strength between the 44 mm 1. IPC-SM-786, Impact of Moisture on Plastic IC Package Crackcover and carrier tapes used in the experiing, December 1990. ment be no less than 10 g and no more than 2. Tom Adams and Steve Martell, “The Moisture Sensitivity Stan130 g.7 dard Goes Pb-Free,” Circuits Assembly, January 2007. • Cover tape peel strength testing. Taped assem3. Ibid. blies exposed to novel baking were cover 4. Rae Levy and Ishayau Perelman, Vacuum Oven Study, Aug. tape peel-strength tested by Advantek (Fig25, 1997. ure 4). Advantek reported, “The two spikes 5. EIA-481C, 8 mm through 200 mm Embossed Carrier Taping above 130 g can be attributed to minor and 8 mm & 12 mm Punched Carrier Taping of Surface Mount waves that developed along the edges of the Components for Automatic Handling, November 2003. sealing flanges of the carrier. If the carrier 6. Peter A. Swanson, Advantek Inc. is not relatively flat, the peel force test … 7. EIA-481C, 8 MM through 200 mm Embossed Carrier Taping can have the peeled cover tape come into and 8 mm & 12 mm Punched Carrier Taping of Surface Mount contact with cover tape that is still adhered. Components for Automatic Handling, November 2003. This friction can cause the spiking seen on 8. Peter A. Swanson, Advantek Inc. the chart and would not represent a true increase in the adhesive bond between the Charles S. (Stu) Leech Jr. is director of engineering at Innovacover and carrier.”8 tive Drying Co. LLC; sleech@qwest.net. • High-impact polystyrene reel deformation. 70°C Table 1. Experimental Samples Package Category Lead Count Body Size in/mm Body Thickness in/mm Molding Compound Supplier/Formula MSL* Visit us at Productronica, Area A3, Booth 578 circuitsassembly.com Circuits Assembly NOVEMBER 2007 45 http://www.ersa.com http://www.ersa.com http://circuitsassembly.com

Table of Contents Feed for the Digital Edition of Circuits Assembly - November 2007

Circuits Assembly - November 2007 Contents Caveat Lector Industry News Market Watch Talking Heads Focus on Business Global Sourcing On the Forefront Screen Printing Better Manufacturing Pb-Free Manufacturing from a Tier III EMS Perspective ‘Living Documents, Subject to Change’ Creating Ideal Solder Joints An Alternative Drying Process for MSDs ‘Customer Satisfaction is More than a Score’ Optoelectronic Substrates: Will They Happen? Tech Tips Wave Soldering Process Doctor Test and Inspection Getting Lean Materials World Equipment Advances Product Spotlight Assembly Insider Technical Abstracts Ad Index

Circuits Assembly - November 2007

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.