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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
2.1.3 Relationship of mount pad size and tolerance

Figure 2-2. Relationship Between Shift of Pin from Center Position and Mount Pad


If the mount pad's width is assumed to be 0.76 mm MIN, then there will be an overlap margin of 0.07 mm MIN between the SOP pin's edge and the mount pad's edge.

The allowable range is wider if the pin width is smaller than the maximum dimensions.
The positional tolerance is as follows when the pin width is the minimum value.

The pin positional tolerance x

 = 2 x [b MAX./2 + x/2 - b MIN./2]
= 2 x [0.50/2 + 0.12/2 - 0.35/2]
= 0.27mm

Therefore a range of up to ±0.135 from the logically accurate dimension position is allowable.

To 2.1.2 Pin existence range calculationTo 2.1.4 Example of mount pad dimension classified by package