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9.2.2 Plated-Through Holes
The maximum and minimum plated-through hole diameters used to attach component leads or pins to the printed board shall be evaluated in accordance with Table 9-3. Both minimum and maximum leads shall be taken into consideration in evaluating the finished plated-through hole requirements. If the lead is a ribbon lead, the minimum and maximum diagonal of a flat ribbon lead shall be considered. Table 9-3 shows the limits of the plated-through hole.
These limits shall be optimized so that manufacturability is enhanced to provide the most liberal tolerances allowable (see Figure 9-3).
Unless otherwise specified, the hole size shall be the finished plated size after solder coating or final plating and fusing, if required. The hole size shall be specified on the master drawing. Plated-through holes used for functional interfacial connections shall not be used for the mounting of devices which put the plated-through hole in compression. Plated-through holes used for functional interfacial connections shall not be used for the mounting of eyelets, solder terminals, or rivets. Plated-through holes shall be used for all interfacial connections on multilayer boards Type 3 through Type 6 (inclusive). Platings and coatings shall be in accordance with IPC-2221.
From IPC-2221:DerStrom8 could you elaborate on what Level A-C are?
1.6.3 Producability Level
When appropriate this standard will provide three design producibility levels of features, tolerances, measurements, assembly, testing of completion or verification of the manufacturing process that reflect progressive increases in sophistication of tooling, materials, or processing and, therefore progressive increases in fabrication cost. These levels are:
Level A General Design Producibility -- Preferred
Level B Moderate Design Producibility -- Standard
Level C High Design Producibility -- Reduced
The producibility levels are not to be intepreted as a design requirement, but a method of communicating the degree of difficulty of a feature between design and fabrication/assembly facilities....