PCB Technical - International requirements for PCB pads are formulated

The 6118 standard of the International Electrotechnical Commission IEC InternationalEletrotechnicalCommission recognizes the need for different targets for solder fillet or pad bump conditions. This new international standard recognizes two basic methods for providing information for the development of PCB pad shapes:

1). Accurate data based on industrial component specifications, PCB copy board manufacturing and component placement accuracy capabilities. These pad shapes are limited to a specific component, and have a number that identifies the shape of the pad.

2). Some equations can be used to change the given information in order to achieve a more robust solder connection. This is used in some special situations where it is used for placement or mounting equipment than the accuracy assumed when determining the pad details There are more or less differences.

This standard defines the maximum, medium and minimum material conditions for the pads used to mount various pins or component terminals. Unless otherwise indicated, this standard marks all three "desired targets" as one, two or three.

Level 1: Maximum-for low-density PCB product applications, the "maximum" pad condition is used for wave or flow soldering of leadless chip components and leaded fin components. The geometry configured for these components and the inward "T"-shaped pin components can provide a wider process window for manual soldering and reflow soldering.

Level 2: Medium-Products with a medium level of component density can consider this "medium" land geometry. It is very similar to the IPC-SM-782 standard pad geometry. The medium pads configured for all component types will provide a robust soldering condition for the reflow soldering process, and should be used for leadless components and fin-shaped components. Wave crest or flow soldering provides proper conditions.

Level 3: Minimum-products with high component density, usually portable product applications, "minimum" land geometry can be considered. The choice of minimum land geometry may not be suitable for all products. Before adopting the smallest land shape, the use of this should consider the product's restriction conditions, and conduct tests based on the conditions shown in the table.

The pad geometry provided in IPC-SM-782 and configured in IEC61188 should accommodate PCB component tolerances and process variables. Although the pads in the IPC standard have provided users with a robust interface for most assembly applications, some companies have expressed the need to use minimum pad geometries for portable electronic products and other unique high-density applications. application.

The international PCB land standard (IEC61188) understands the requirements for higher part density applications and provides information on land geometry for special product types. The purpose of this information is to provide the appropriate size, shape, and tolerances of the surface mount pads to ensure adequate areas for proper PCB soldering fillets, and to allow inspection, testing, and rework of these solder joints.