Bare board

Mounting the steps to the porch like they were a steep hill, he found the front door open a crack. It gave into a simple hall and a brisk scout of the downstairs rooms suggested that the evacuees had departed in orderly fashion, taking many furnishings and ornaments with them. Bare boards, bare mantels, just a few chairs and little else. 

Shales was still for a moment, then bowed and turned suddenly to me. Mistress Selden, if you ever have time to call, I should be delighted to show you my most recent work with plants and airs, and to hear your views. He crossed the room a few paces toward me, but I wouldn t look at him or offer my hand for fear of my father. The door closed, and I heard the sound of his feet on the bare boards in the entrance hall. 

The PCB used in the above procedure can be just a bare board with no components mounted on it, other than the transformer. Or it can even be a fully assembled board (though sometimes, we may need to cut the trace connecting the drain of the mosfet to the transformer). 

In pg NaCl/cm. A value of 0.28 is baseline for an uncontaminated bare board. 

Cleaning applications in the SMT assembly line typically start with the cleaning of the bare boards (1). The preliminary substrates have to be cleaned in order to remove a variety of residues (particles, chemicals used in the manufacturing process of the bare boards). These residues may have a negative impact on the subsequent production steps. A detailed analysis of different kinds of contamination which might occur on the bare boards revealed... 

Speedline Aquajet Spray semiautomatic batch-cleaning systems typical applications include bare boards, stencils, misprints, pallets, and PCB assemblies Water soluble, saponified, compatible with aqueous detergents and deionized water Compatible with most combustible semi-aqueous solvents EC7-R typical N/A... 

A type I bare board will first have solder paste applied to the component pads on the board. Once solder paste has been deposited, active and passive parts are placed in the paste. For prototype and low-volume lines this can be done with manually guided X-Y tables using vacuum needles to hold the components, whereas in medium and high-volume lines automated placement equipment is used. This equipment will pick parts from reels, sticks, or trays, then place the components at the appropriate pad locations on the board, hence the term pick and place equipment. 

After PCB routing and layout have been completed, the output phase begins, where the design is output from the PCB editing system and sent to bare board manufacturing to produce the actual bare board layers and then laminate, drill, and finish them. 

When PC boards are ready, the design data together with the boards are sent to assembly houses, where the components from the bill of materials (BOM) are assembled onto the finished bare board at the locations specified by the design. 

Bare board fabrication and board assembly share some common data elements but also have distinct data needs. Examples of common elements are the outer circuit and mask layers and through-driU information. Unique data elements are, for example, inner layers for board fabricators and component placement locations and functional component descriptions for assembly houses. AU these data elements are described in the next section. 

Component Information BOM and AVL. A PCA may be designed for more than one product variant and to support future functionality. Therefore, for almost all designs, some of the reference designators (or actual bare board footprints on which components can be placed) will not be populated for all assembled board orders. BOM files are used to teU the assembler which reference designators should actually be placed on a given board for a specific order. 

Netlist Formats. A netlist is a set of connection points joined together to form networks. Each point represents a contact point on the surface of a bare board. A connection point can be either a drilled hole or a surface mount pad. All points belonging to one network should be connected to each other through PCB layer circuitry and/or power and ground planes. 

There are fwo amendments to IPC-D-356 IPtD-356A and IPC-D-356B. Most of the extra information included in these formats is important for bare-board electrical testing and, unless buried passives are used, the information is generally not needed for CAD-to-CAM data consistency verification. If buried passives are used, it is better to transfer IPC-D-356A after verifying readability by the supplier. 

ODB++. The ODB++ data format is a common language used for DEM and CAD/CAM data exchange. It overcomes many data communication obstacles within design/manufacturing supply chains. Data in this powerful open database impart an integrated and accurate physical model of all bare-board, component, and test-related information. It is designed as a simple yet comprehensive description of all entities used in the manufacture and assembly of a PCB. 

IPC-2581 is actually a series of IPC-258x documents, where x represents 1-9 IPC-2581 consists of the generic requirements (or, in this case, the full format description), whereas IPC-2582 and above are sectional requirements. IPC-2584, for example, contains the sectional requirements for fabrication and explains which generic IPC-2581 elements are required for bare-board fabrication and which elements are optional. 

Bare-Board Analysis. Several physical artwork problems are not discovered by design rule checking and are not strictly speaking the result of design rule violations. Nonetheless, these problems can affect the manufacturabiUty of a board and its yield. Table 20.5 describes some of these issues. 

The bare-board base materials are identified by using the classification system found in IPC-4101, which has specification sheets for various grades of material. The specification sheet is also known as a slash sheet since each material specification is preceded by a forward slash (/). Each sheet s heading typically identifies the resin system, the reinforcement, flame retardant, presence of fillers, as well as some performance parameters, such as glass transition temperature (Tg) or decomposition temperature (Tj). More detail is in Sec. 27.2.2. 

To ensure good soldering, it is necessary for the assembler to ensure that aU copper is protected and no solder mask residue remains on solderable featnres. By inspecting the bare board, the engineer can reject parts that show bare copper due to skipped surface finishing or mask residue. A special case is OSP, where inspection of the protected copper is impossible because OSP-protected areas have the same visual appearance of uncoated copper with or without thin solder mask contamination. 

Final determination of the suitability of a given set of requirements must be made in cooperation with technical representatives of the bare board purchaser. 

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