barcode scanner integration in FIGURE 32.2 in Software

Drawer Denso QR Bar Code in Software FIGURE 32.2

Quick Response Code Recognizer In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
Paint Quick Response Code In None
Using Barcode drawer for Software Control to generate, create QR-Code image in Software applications.
(a) HASL equipment (b) surface scanning electron micrograph (SEM).
QR Code Decoder In None
Using Barcode decoder for Software Control to read, scan read, scan image in Software applications.
Generate QR-Code In Visual C#
Using Barcode encoder for VS .NET Control to generate, create QR-Code image in .NET applications.
Draw QR Code 2d Barcode In .NET
Using Barcode creator for ASP.NET Control to generate, create Denso QR Bar Code image in ASP.NET applications.
Paint QR Code JIS X 0510 In .NET Framework
Using Barcode creator for .NET Control to generate, create QR Code 2d barcode image in VS .NET applications.
Create QR Code In Visual Basic .NET
Using Barcode drawer for VS .NET Control to generate, create QR image in VS .NET applications.
Encode Barcode In None
Using Barcode creation for Software Control to generate, create bar code image in Software applications.
Chemically, gold is the ideal element for the external coating of PCBs. Gold does not form an oxide, so it is virtually unaffected by temperature and storage conditions that might reduce the shelf-life of other finishes. In addition, gold dissolves nearly instantaneously into solder, promoting superior wettability. Gold is limited, however, in other ways. Gold embrittles solderjoints when present in excess of about 3 percent by weight, so gold coatings of 0.3 mm maximum thicknesses should be used in soldering. Gold dissolves very quickly into copper as well. To prevent the mixing of gold with copper, and the eventual solderability problems caused by oxidized copper at the PCB surface, a layer of nickel is deposited to separate the metals. ENIG does not rely on electrolytic plating with outside power; in practice, nickel is deposited as a phosphorous-reduced electroless nickel. 32.4.1 Chemistry ENIG deposition is dependent on the electromotive series of elements. Gold readily deposits directly on copper as an immersion bath, but as stated previously, a barrier of nickel is needed. In common practice, 3 to 5 mm of nickel is used in ENIG, with a thin gold coating of 0.05 to 0.15 mm (typically) to prevent nickel oxidation. Nickel does not deposit directly on copper without prior catalysis. Palladium or ruthenium metal forms an immersion deposit on copper as the catalysis or activation step of ENIG. Catalysis baths employ the immersion (galvanic displacement) chemical mechanism. As with all finishes, extra steps are required before the deposition of catalyst, Ni, and Au. All commercial ENIG processes rely on a cleaner and microetch prior to catalysis in order to remove trace residues from the solder mask and tin strip processes before final finish. Microetch is normally based on peroxide, persulfate, or monopersulfate systems. 32.4.2 Fabrication Process Table 32.3 shows the process flow for ENIG surface finish.
Generate Code 128A In None
Using Barcode generator for Software Control to generate, create Code 128 Code Set B image in Software applications.
Code 39 Extended Printer In None
Using Barcode generation for Software Control to generate, create USS Code 39 image in Software applications.
TABLE 32.3 Process Flow for ENIG Time (min.)
EAN / UCC - 13 Printer In None
Using Barcode maker for Software Control to generate, create European Article Number 13 image in Software applications.
Universal Product Code Version A Creation In None
Using Barcode creator for Software Control to generate, create UPC-A Supplement 2 image in Software applications.
Process Cleaner Microetch
Making Royal Mail Barcode In None
Using Barcode creator for Software Control to generate, create Royal Mail Barcode image in Software applications.
Bar Code Printer In None
Using Barcode generator for Font Control to generate, create barcode image in Font applications.
Chemicals Aqueous solvents, detergents, and emulsifiers. Acid can help undercut residues and remove thick copper oxides. In acidic environments, copper is oxidized by persulfate (S2O8++), peroxide (H2O2), or proprietary monopersulfate acid mixes. Sulfuric acid is common to all types of microetch. 1 2 mm of Cu is oxidized to Cu++ and dissolved. Immersion deposit (galvanic displacement) Pd++ + Cu(0) Pd(0) + Cu++ (or) Ru+++ + Cu(0) Ru(0) + Cu++ Nickel is deposited through chemical (sodium hypophosphite) reduction. Rate control, by pH and temperature, determines phosphorous content, usually 8 11% by weight. Normally, automated controllers are needed to maintain this dynamic bath. Nickel can be measured optically or with titration. Ammonia maintains pH.
Barcode Drawer In VS .NET
Using Barcode drawer for Visual Studio .NET Control to generate, create bar code image in VS .NET applications.
GTIN - 13 Reader In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
Generate Code128 In Objective-C
Using Barcode encoder for iPhone Control to generate, create Code 128B image in iPhone applications.
Draw Data Matrix ECC200 In Objective-C
Using Barcode generator for iPhone Control to generate, create DataMatrix image in iPhone applications.
Electroless Nickel
Scan Code 39 Extended In Java
Using Barcode reader for Java Control to read, scan read, scan image in Java applications.
Drawing GS1 - 12 In Java
Using Barcode drawer for Eclipse BIRT Control to generate, create UPC Symbol image in Eclipse BIRT applications.
10 20
Immersion Gold
Immersion deposit (galvanic displacement) Au+ + Ni(0) Au(0) + Ni++ Gold is added as KAu(CN)2. Do not use gold salts containing Co or Ni.
8 15
Due to the long dwell times, high operating temperatures, and complicated chemical reactions, the ENIG process is always conducted in vertical tanks. To achieve the throughput required in production, many ENIG systems make use of two or three electroless nickel (EN) tanks, which allows for heating new baths or nickel stripping. Using two active EN tanks greatly improves throughput, but the total process ordinarily exceeds 1 hour in cycle time. In addition to the normal plastic materials used in tank construction, stainless steel can be used for EN tanks. This is possible only with the use of anodic passivation, which employs an electrical bias applied to the steel to prevent reduction of nickel ions on the steel. By using steel tanks, fabricators avoid the frequent stripping of plastic tanks required due to the slow plate-out of nickel on rough surfaces and localized hot spots.
Advantages and Disadvantages Table 32.4 shows comparison of advantages and disadvantages of ENIG surface finishes.
TABLE 32.4 Advantages and Disadvantages of ENIG ENIG advantages Flat; fine-pitch assembly Surface contacts Widely available No copper dissolution No Pb Strong PTH rivet Long shelf-life ENIG disadvantages Expensive Brittle Ni/Sn solderjoint Not reworkable Solder mask attack Black-pad, black-line nickel Signal loss at RF frequencies Very complicated process
Failure Modes ENIG failure modes at fabrication are mainly due to the activity of the chemical process steps. Underactive catalysis yields skip plating in the subsequent nickel bath. Nickel skips allow copper to migrate through gold and prevent solder wetting. Overactive catalysis can lead to extra metal between circuit features, known as extraneous plating. This can cause short circuits. Overactive nickel baths deposit low phosphorous content, leading to the interconnection failure mode known as black-pad (described in Sec. 12.2). Overactive gold chemistry attacks nickel along nodule boundaries and produces black-pad. Such gold conditions may be detected with frequent x-ray fluorescence (XRF) thickness measurement. Underactive nickel and gold baths pose skip-plate problems. Peeling of gold films can result from too much rinse time after nickel or from poor rinse quality. Tape testing of ENIG is mandatory. Very rough nickel deposits are possible when the electroless nickel bath is not closely maintained. Nickel baths can destabilize, plate onto the tank walls, and produce inferior coatings. Lastly, soldered ENIG surfaces result in a nickel-tin solderjoint. This structure has been demonstrated to be less tolerant of physical shock than the copper-tin solderjoint. The brittle intermetallic is unavoidable with ENIG, so mobile devices usually do not employ ENIG solderjoints.
Copyright © . All rights reserved.