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1、ENA STANDARD Definition and Regider, printed Wiring (Reaffirmed February 1970) F e b r m 1958 Engineering Department ELECTRONIC INDUSTRIES ASSOCIATION Copyright Electronic Components, Assemblies the span for the inner radius shall lie between the radii of$he outer span. (See Fig. 2) (c) For “curved”
2、 edges wherein the mini- mum radius of curvature is less than one-half inch (13 mm), the span shall be the entire curved portion if the edge changes course less than ninety degrees, or shall be ninety degrees of the edge if the change in course equals or exceeds that. (See Fig. 3) - H - - - Fig. 1 F
3、ig. 2 Fig. 3 Copyright Electronic Components, Assemblies they shall not be included in measurements unless specified to be included for critical areas (2.2.1 and 2.2.2). 2.1.3 Specification of definition shall be simple crest-to-trough measurement, in thousandths of an inch, or millimeters, acceptab
4、le in each case. (a) Such specification must take into account any edge roughness of the Master Pattern. 2.2 Area and size variation shall be measured -by comparison with the dimensions of the Master Drawing. 2.2.1 The width of parallel-edged conductors shall be measured with the instrument of 2.1.1
5、. The mean width within the stated spans of 2.1.2 shall be deemed the distance between the means of the two crest-to-trough edge measurements; this is the distance between a line half-way between crest and trough maxima of one edge to a like line of the other edge. (See Fig. 4) (a) Special specifica
6、tion of maximum and minimum widths (and related spacings), and of blemishes, shall be applied to those critical areas where these factors assume importance. MAX. Fig. 4 2.2.2 In like manner, other areas shall be compared, using the “mean edge” as the dimension line or envelope of the conductor, with
7、 maximum and minimum departure therefrom given special Specification as in 2.2.1 (a). 2.2.3 Specification of size or area shall use the methods of 2.2.1 and 2.2.2. 3. REGISTER 3.1 Register of conductors to holes and boundaries of a board shall be measured as departure from congruity of actual hole c
8、enters with actual conductor area printing centers, and as departure from intended conductor-to-board-boundaiy dimensions. 3.1.1 The instruments of 2.1.1 shall be used for distances within their capabilities; they permit fmding hole centers and conductor centers in small areas such as terminal areas
9、. Height-gauges or steel scales viewed thru a magnifier are more suitable for distances exceeding one-half inch (13 mm). a Copyright Electronic Components, Assemblies therefore, register is measurable as the departure from congruity, in thousandths of an inch, or millimeters, using the mean edge of
10、2.2.1 as the envelope of any area. (a) Specification of register shali be made in each case in terms of required tolerance of congruity. (See Fig. 5) (b) Inspection of printed wiring may also include determination of accuracy of hole layout dimensions in view of the physical part drawing, as is cust
11、omary in any manu- factured part, and should aiso, then, deter- mine the accuracy of the conductor place- ment itself as the second size-control neLes- sary for register. I l Fig. 5 3.1.3 Two-sided register shall be in terms of 3.1.2 (a) for each side, unless greater control is required, in which ca
12、se specification shall be for direct tolerance of printing on one side to that on the other, but measurement shall be made to holes as before. 4. EDGE CROSS-SECTION SHAPE 4.1 The normally desired conductor cross-section is rectangular. 4.1.1 Specification of cross-section is to be made in terms of t
13、he deviation from a perfect rectangular shape; this shall be suited to the method of manufacture. (a) Width variation thru the thickness and thickness variation thru the width, as well as gross edge effects shall be specified in thousandths of an inch, or millimeters, or in finer measure as required. c o Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 20:18:58 MDTNo reproduction or networking permitted without license from IHS -,-,-