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Products > Packages > Semiconductor Device Mount Manual > PRINTED WIRING BOARD DESIGN > Lead-type SMDs >

CHAPTER 2 PRINTED WIRING BOARD DESIGN


2.1 Lead-type SMDs
2.1.2 Pin existence range calculation

[ Combination of pin width tolerance and positional tolerance ]: indicating pin existence range
Combination of pin width tolerance and positional tolerance (equation)(2.16KB)

A description of geometrical tolerance is shown below.

Table 2-1. Description of Geometrical Tolerance
Symbol(211B) Symbol indicating the positional tolerance.
Numerical value indicating that the positional tolerance of the pin center is in the range of x = 0.12 mm.
Symbol indicating that the positional tolerance can be up to x = 0.12 mm, based on a pin width of b MAX = 0.50 mm.
(i.e. If the pin width b is less than the maximum value, the tolerance will be greater than x = 0.12 mm)


A concrete calculation example is shown below.

The allowable existence area of pin width direction
= 2 x [b MAX./2 + x/2] = 2 x [0.50/2 + 0.12/2]
= 2 x [0.62/2] = 0.62 mm

This relationship is shown in Figure 2-2 on the next page.

To 2.1.1 Tolerance of package dimensionsTo 2.1.3 Relationship of mount pad size and tolerance