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INSTRUCTIONS TO BE FOLLOWED IN MOUNTING 3.4 Permissible error margin for the lead center position Abstract from EIAJ standard ED-7404

(2) Definition of "lead center position permissible error margin"

MITSUBISHI INTEGRATED CIRCUIT PACKAGES
INSTRUCTIONS TO BE FOLLOWED IN MOUNTING 3.4 Permissible error margin for the lead center position (Abstract from EIAJ standard ED-7404)
An increasing number of contour design directions, issued either in or outside Japan, indicate the permissible error margin for the lead center position (reference code: x) with geometric tolerance plus an additional code. The permissible error margin is related to the interval in a straight line between leads (true geometric position) and lead width. The permissible error margin for the QFP lead center position is outlined below, along with the identification system. (1) Indication system The lead center permissible error margin x is not a dimensional value that exists alone. It is indicated as shown below.
Maximum-body condition...Indicates that the value is based on limit dimensions where the body is maximum. Lead center position permissible error margin (tolerance) Position tolerance code...Indicates the permissible error margin from the true center position. Lead width (indicated with the reference dimension and dimensional allowance)
(2) Definition of "lead center position permissible error margin"
Center line at a specified, correct position
The range of the space between two lines that are parallel to each other when the lead width (b) is maximum. The distance between the lines is as expressed by value x from the center line at a specified, correct position.
In the direction of arrows
Fig.19
LEAD CENTER POSITION PERMISSIBLE ERROR MARGIN
MITSUBISHI INTEGRATED CIRCUIT PACKAGES
INSTRUCTIONS TO BE FOLLOWED IN MOUNTING
True center position Center position at bmax Center position at bmin
Center position error at bmin
bmax x + bmax 2 2 Lead half width with respect to the true center position when the lead position error is at the larger limit.
Center position error at bmax
Fig.20
LEAD POSITION ERROR TO THE RIGHT-HAND SIDE