1、ENA STANDARD Definition and Regider, printed Wiring (Reaffirmed February 1970) Febrm 1958 Engineering Department ELECTRONIC INDUSTRIES ASSOCIATION I - v EIA 208 58 W 3234b00 00b2953 4 W II NOTICE EIA engineering standards are designed to serve the public interest through eliminating mis- understandi
2、ngs between manufadurers and pychasers,.facilitating interchangeability and improve- ment of products, and assisting the purchaser m selecting and obtaining with minimum delay the proper product for his particular need. Existence of such standards shall not in any respect pre- clude any member or no
3、n-member of EIA from manufacturing or selling products not conforming to such standards, nor shall the existence of such standards preclude their voluntary use by those other than EIA members whether the standard is to be used either domestically or internationally. Recommended standards are adopted
4、 by EU without regard to whether or not their adoption may involve paterits on articles, materials, or processes. By such action, EIA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the recommended standards. Published by J3LECTRONIC
5、INDUSTRIES ASSOCIATION Engineering Department 2001 Eye Street, N. W., Washington, D. C. 20006 Copyright 1970 by Electronics Industry Association Printed in U.S.A. EIA 208 58 W 3234600 00b2954 b W RS-208 Page 1 DEFINITION AND REGISTER, PRINTED WIRING (Reaffirmation of RS-208) 1. SCOPE AND MEANINGS De
6、finition and register of all forms of printed wiring are included. “Definition” is the degree of faithfulness of reproduction of conductor referred to the Master Pattern. “Register” is the degree of alignment of conductor with intended position on the printed wiring board. 2. DEFINITION 2.1 accordan
7、ce with the following technique. Edges of conductors shall be measured for sharpness of production and reproduction in % 2.1.1 An optical instrument with a measuring reticle is to be used. It may be any form of microscope or any form of hand magnifying instrument with a readability to one one-thou-
8、sandth inch (.O2 mm). 2.1.2 Viewed thru the instrument, the conductor edge is to be measured for the maximum crest-to-trough of its roughness, in thousandths of an inch, or millimeters, within the spans specified. (See Fig. 1) Locations of spans may be random or designated. (a) one-half inch (1 3 mm
9、). (See Fig. 2) For “straight” edges the span is to be (b) For “curved” edges the span is to be one-half inch. (13 mm) along the curve if the minimum radius of curvature be one-half inch (13 mm) or more. This includes curves of single radius or of variable radius. (See Fig. 2) (1) For parallel edged
10、 curved conduc- tors, the outer radius shall govern; the span for the inner radius shall lie between the radii of$he outer span. (See Fig. 2) (c) For “curved” 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 c
11、hanges 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 Fig. 2 Fig. 3 EIA 208 58 m 3234600 0062955 m c RS-208 Page 2 (d) Blemishes, such as isolated projections or indentations shall be treated as manufac
12、tur- ing errors; 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, acceptable in each case. (a) Such specification
13、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. The mean width within the stated spans
14、 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 specification of maximum and minimum widths (and
15、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 maximum and minimum departure therefrom
16、 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 centers with actual conductor area printi
17、ng 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. Height-gauges or steel scales viewed t
18、hru a magnifier are more suitable for distances exceeding one-half inch (13 mm). a EIA 208 58 E 3234b00 0062956 T m RS-208 Page 3 3.1.2 Superposability of conductor centers upon hole centers is the intention- in this type of work; therefore, register is measurable as the departure from congruity, in
19、 thousandths of an inch, or millimeters, using the mean edge of 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 la
20、yout dimensions in view of the physical part drawing, as is customary 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
21、) for each side, unless greater control is required, in which case 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.
22、4.1.1 Specification of cross-section is to be made in terms of the 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
