barcode scanner code in asp.net PRINTED CIRCUITS HANDBOOK in Software

Encoding Denso QR Bar Code in Software PRINTED CIRCUITS HANDBOOK

PRINTED CIRCUITS HANDBOOK
QR Code JIS X 0510 Decoder In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
Create QR In None
Using Barcode creator for Software Control to generate, create QR Code 2d barcode image in Software applications.
FIGURE 40.7
Quick Response Code Reader In None
Using Barcode scanner for Software Control to read, scan read, scan image in Software applications.
Quick Response Code Creation In C#
Using Barcode generator for .NET framework Control to generate, create QR Code image in Visual Studio .NET applications.
Schematic diagram showing the wave-soldering process.
QR Code 2d Barcode Encoder In .NET Framework
Using Barcode creation for ASP.NET Control to generate, create QR Code image in ASP.NET applications.
QR Generator In .NET
Using Barcode drawer for Visual Studio .NET Control to generate, create QR Code JIS X 0510 image in VS .NET applications.
FIGURE 14.8 Schematic diagram of the dual solder wave configuration.
Encoding Quick Response Code In Visual Basic .NET
Using Barcode maker for .NET Control to generate, create QR-Code image in .NET applications.
Bar Code Drawer In None
Using Barcode creation for Software Control to generate, create bar code image in Software applications.
FIGURE 40.9 Photograph of the dual-wave configuration. (Courtesy of Vitronics-Soltec.)
ECC200 Generation In None
Using Barcode encoder for Software Control to generate, create Data Matrix ECC200 image in Software applications.
Encoding GS1 - 13 In None
Using Barcode generation for Software Control to generate, create GTIN - 13 image in Software applications.
After the fluxing step, the circuit board passes through the preheat stage, which is comprised of a set of radiant heaters. As the circuit board is heated, this step evaporates volatiles from the flux coating (which if not adequately removed can lead to voids and blow holes) and activates the chemical reactions between the flux and oxides on the component lead or termination and the circuit board conductor. The solder wave is created by pumping molten alloy upward through a nozzle, where it exits to a certain height and then falls back into the bath.The solder bath temperature is 260 C for eutectic Sn-Pb solder.The printed circuit board is carried by the conveyor so that is passes over the surface of the wave. The bottom side of the circuit board contacts the wave, allowing the molten solder to wet the exposed pads as well as to flow upward through the holes by capillary action. The speed of the conveyor and the take-off angle that is, the angle at which the circuit board approaches the wave are critical parameters for minimizing wave-soldering defects. Another critical parameter of wave soldering is the wave geometry. The schematic diagram in Fig. 40.8 shows the commonly used dual wave. The first wave is turbulent so as to counteract the surface tension of the molten solder, thereby literally forcing the molten solder into confined geometries in order to initiate the wetting process. The second wave is smooth or laminar. The laminar wave is located at the exit point because its geometry reduces the propensity for bridges and icicle defects to form as the molten solder retracts itself from the circuit board. The photograph in Fig. 40.9 shows a circuit board entering the turbulent wave of a dual-wave soldering system. A variation of wave soldering is the so-called selective soldering process. Instead of using a long wave to accommodate
Code 39 Generation In None
Using Barcode generator for Software Control to generate, create Code 39 Full ASCII image in Software applications.
UPCA Generation In None
Using Barcode generator for Software Control to generate, create UPC Symbol image in Software applications.
ASSEMBLY PROCESSES
I-2/5 Drawer In None
Using Barcode printer for Software Control to generate, create 2 of 5 Interleaved image in Software applications.
Code 128 Code Set A Recognizer In .NET Framework
Using Barcode reader for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications.
the dimensions of an entire circuit board, a small fountain is created of molten solder. The reduced geometry allows for the soldering of individual components or several components on only selected areas of the circuit board.A manual operation is used to apply flux and preheat the circuit board prior to the actual soldering process. The change to Pb-free solders has affected the wave-soldering process. Fortunately, the 260 C bath temperature used with eutectic Sn-Pb solder has proven to be adequate for most applications using the 99.3Sn-0.7Cu (wt. percent) and Sn-Ag-Cu alloys. Some users have preferred to raise the pot temperature to 260 to 270 C. The elements Ni and Ge have been added to the Pb-free solders in order to provide the shiny fillets that inspectors are accustomed to observing with Sn-Pb solders. The higher surface tension of the Sn-based, Pb-free solders increases the tendency for opens, bridges, and icicles to form as the circuit board exits the wave. A change of flux chemistry as well as adjustments to the take-off angle and conveyor speed have been used to minimize those defects. Lastly, a particular problem with Pb-free wave soldering is erosion of the machine parts by the high-Sn alloy compositions. Special coatings are put on the impeller, nozzles, baffles, and bath walls to mitigate the erosion process. 40.2.7 Paste-in-Hole (Pin-in-Paste) Soldering Very rapid production volumes are realized with inline surface-mount assembly processes. In general, the surface-mount assembly process consists of three basic steps: (a) screen printing of solder paste, (b) pick and place of components, and (c) reflow of the solder paste. To obtain similar throughputs for through-hole circuit boards, paste-in-hole soldering is being investigated as an alternative to wave soldering. Solder is provided to the joint in the form of a paste, using screen or stencil printing, or dispensed from a needle. The component is then inserted into the hole. In some applications, the parts are inserted into the circuit board and subsequently the solder is dispensed at the hole using a needle and pump. Then the assembly is sent through the reflow furnace. The primary hurdle with paste-in-hole soldering is supplying a quantity of paste that is sufficient not only to develop a fillet on that side of the joint, but also to fill the hole and, optimistically, create a fillet on the bottom side of two-sided and multilayer circuit boards. A second concern for paste-in-hole soldering is the temperature sensitivity of the throughhole components. Recall that in wave, selective, or even hand soldering, the temperature rise is confined largely to the leads and circuit board. At worst, the component package materials experience only the preheat temperature environment. However, in paste-in-hole soldering, components must withstand the soldering temperatures within the reflow furnace. Therefore, a conversion to this solder process requires an in-depth review of the allowable temperature range for all of the components. 40.2.8 Cleaning The final step in the soldering process is the removal of flux residues from the completed circuit board. No-clean fluxes, as the name implies, produce residues that need not be removed from the assembly after soldering. The corrosive activators are locked up in a hard, polymerized residue. However, no-clean flux residues can potentially interfere with in-circuit testing (probes) and inspection, degrade cosmetic appearance, inhibit rework activities, and lessen the adhesion of conformal coatings. In the event that any one of these factors becomes critical, it is best to switch to a cleanable flux than to develop a cleaning process for a no-clean flux. Low-solids fluxes (which are not to be confused with no-clean fluxes) are simply formulated with reduced solids content so that very little residue is left on the circuit board. Lowsolids flux can be successfully used in wave-soldering and paste-in-hole processes, thereby eliminating the need for a cleaning step. However, they are somewhat more difficult to use in hand-soldering processes because the higher temperature of the soldering iron tip can cause premature loss of the activating agent, resulting in poor solderability.
Draw Bar Code In Visual Studio .NET
Using Barcode maker for .NET framework Control to generate, create barcode image in .NET applications.
Bar Code Generator In VS .NET
Using Barcode creator for Reporting Service Control to generate, create bar code image in Reporting Service applications.
Print Linear In Visual Basic .NET
Using Barcode encoder for .NET Control to generate, create Linear 1D Barcode image in .NET applications.
DataMatrix Decoder In None
Using Barcode scanner for Software Control to read, scan read, scan image in Software applications.
Encoding GS1-128 In None
Using Barcode generator for Online Control to generate, create EAN / UCC - 13 image in Online applications.
Creating Barcode In Java
Using Barcode generator for BIRT reports Control to generate, create bar code image in BIRT reports applications.
Copyright © OnBarcode.com . All rights reserved.