1. IPC-2221 5.3.2 Part Support All parts weighing 5.0 gm, or more, per lead shall be supported by specified means, which will help ensure that their soldered joints and leads are not relied upon for mechanical strength. The reliability of printed boards that will be subject to shock and vibration in service require consideration of the following criteria:

2. IPC-2221 5.3.2 Part Support The worst-case levels of shock and vibration environment for the entire structure in which the printed board assembly resides, and the ultimate level of this environment that is actually transmitted to the components on the board. (Particular attention should be given to equipment that will be subjected to random vibration.)

3. IPC-2221 5.3.2 Part Support The method of mounting the board in the equipment to reduce the effects of the shock and vibration environment, specifically the number of board mounting supports, their interval, and their complexity. The attention given to the mechanical design of the board, specifically its size, shape, type of material, material thickness, and the degree of resistance to bowing and flexing that the design provides.

4. IPC-2221 5.3.2 Part Support The shape, mass and location of the components mounted on the board. The component lead wire stress relief design as provided by its package, lead spacing, lead bending, or a combination of these, plus the addition of restraining devices.

5. IPC-2221 5.3.2 Part Support The attention paid to workmanship during board assembly, so as to ensure that component leads are properly bent, not nicked, and that the components are installed in a manner that tends to minimize component movement. Conformal coating may also be used to reduce the effect of shock and vibration on the board assembly.

6. IPC-2221 5.3.2 Part Support Where circuit design permits, the selection of components to be mounted on boards subjected to severe shock and vibration should favor the use of components that are lightweight, have low profiles and inherent strain-relief provisions. Where discrete components must be used, preference should be given to surface mount and/or axially- leaded types that present a relatively low profile that can be mounted and easily clamped or bonded in intimate contact with the board surface.

7. IPC-2221 5.3.2 Part Support The use of irregularly-shaped components, especially those having a large mass and a high center of gravity, should be avoided where practical. If their use cannot be avoided, they should be located toward the outer perimeter of the board, or where hardware or mounting reduces flexing. Depending on the severity of this problem, the use of mechanical clamping, adhesive bonding, or embedding may be required.