1、 EIA STANDARD TP-112 Contact Resistance and Current Rating of Parallel Circuits Test Procedure for Electrical Connectors, Contacts and Sockets EIA-364-112 January 2010 Electronic Components Industry Association ANSI/EIA-364-112-2010 (R2016) Approved: January 14, 2010 Reaffirmed: April 13, 2016 EIA-3
2、64-112NOTICE EIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minim
3、um delay the proper product for his particular need. Existence of such Standards and Publications shall not in any respect preclude any member or nonmember of ECIA from manufacturing or selling products not conforming to such Standards and Publications, nor shall the existence of such Standards and
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5、A does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard or Publication. This EIA standard is considered to have International Standardization implications, but the International Electrotechnical Commission activity has not prog
6、ressed to the point where a valid comparison between the EIA standard and the IEC document can be made. This Standard does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Standard to establish
7、appropriate safety and health practices and to determine the applicability of regulatory limitations before its use. (From Standards Proposal No. 5179 and reaffirmed by Standards Proposal No. 5361.07, formulated under the cognizance of the EIA CE-2.0 Committee on National Connector and Socket Standa
8、rds). Published by ELECTRONIC COMPONENTS INDUSTRY ASSOCIATION 2016 Standards & Technology Department 2214 Rock Hill Road, Suite 265 Herndon, VA 20170 PLEASE ! DONT VIOLATE THE LAW! This document is copyrighted by the ECIA and may not be reproduced without permission. Organizations may obtain permiss
9、ion to reproduce a limited number of copies through entering into a license agreement. For information, contact: IHS 15 Inverness Way East Englewood, CO 80112-5704 or call USA and Canada (1-877-413-5186), International (303-397-7956) CONTENTS Clause Page 1 Introduction . 1 1.1 Scope . 1 1.2 Object 1
10、 1.3 Background . 1 1.4 Prerequisites 2 2 Definitions 2 3 Test method . 2 3.1 Method A, central limit theorem parallel contact resistance 2 3.2 Method B (reserved for future use) 3 4 Details to be specified . 3 5 Test documentation . 4 Table A.1 Test groups A-1 A.2 Test results A-2 A.3 Monte Carlo s
11、imulation results . A-3 A.4 Histogram results A-4 A.5 Distribution of parallel resistance means results A-6 A.6 Unit-to-unit variation relative to the pin-to-pin variation . A-7 Annex A Method A, example central limit theorem parallel contact resistance (informative) A-1 A.1 Test sequences A-1 A.2 R
12、esults . A-2 A.3 Validation A-3 A.4 Histogram results A-4 A.5 Discussion . A-4 A.6 Implementation . A-7 A.7 Summary . A-8 A.8 Notes . A-8 i (This page left blank) ii EIA-364-112 Page 1 TEST PROCEDURE No. 112 CONTACT RESISTANCE AND CURRENT RATING OF PARALLEL CIRCUITS TEST PROCEDURE FOR ELECTRICAL CON
13、NECTORS AND SOCKETS (From EIA Standards Proposal No. 5179, formulated under the cognizance of EIA CE-2.0 Committee on National Connector Standards) 1 Introduction 1.1 Scope This procedure applies to connectors and sockets when multiple circuits are electrically connected in a parallel configuration
14、and there is a need to determine the expected parallel resistance and or current rating. 1.2 Object 1.2.1 This standard establishes a procedure for determining the predicted parallel contact resistance of a connector or socket when multiple circuits are connected in parallel. A statistical approach
15、is employed to determine the parallel or effective contact resistance using empirical data from EIA connector test sequences such as EIA-364-1000. 1.2.2 The procedure for determining current rating of a connector or socket when multiple circuits are connected in parallel will be added in the near fu
16、ture to this document. 1.3 Background Traditional methods for determining low level contact resistance limits for parallel circuits such as a worst case parallel resistance calculation employ extremely conservative calculations that produce limits unlikely to be seen in actual application. This proc
17、edure outlines a more realistic method that is based on sound statistical principles and determines the parallel resistance limit with a percentile derived from calculations made using easily-obtained data. The limit calculated by this standard may be used by system designers to plan their voltage d
18、rop budget. Unrealistically high limits calculated with the previous method result in inefficient use of power resources in an application. Method A applies the Central Limit Theorem to parallel resistance distributions for low power level applications. Method B applies to current rating of parallel
19、 circuits using distribution fitting and Monte Carlo simulation. EIA-364-112 Page 2 1.4 Prerequisites The proposed methods are not a substitute for common connector qualification practices. These methods rely upon said qualification test data. In such tests, a maximum resistance and/or a maximum del
20、ta resistance limit will be applied to individual contact data. It is not appropriate the apply theses methods to products with open circuits or high resistances that do not meet these criteria. Connector products that do not meet these criteria should not be considered qualified for use in an appli
21、cation based solely upon its calculated parallel resistance. The connectors must meet a clear individual contact limit before a parallel resistance is calculated. 2 Definitions 2.1 Parallel circuit Two or more connector or socket circuits electrically connected together on both sides of the separabl
22、e interface. 2.2 Central limit theorem A mathematical theorem that is central to the use of statistics. It states that for a random sample of observations from any distribution with a finite mean and a finite variance, the mean of the observations will follow a normal distribution. This theorem is t
23、he main justification for the widespread use of statistical analyses based on the normal distribution. 3 Test method 3.1 Method A, central limit theorem parallel contact resistance See annex A for an example and additional information. 3.1.1 Identify the end-of-life low level contact resistance meas
24、urements, R, for each stress group in a typical connector qualification test. Calculate the mean ( R ) and standard deviation (sR) of the distribution of R for each test group. 3.1.2 Determine the number of contacts (n) in the parallel circuit for the connector of interest. 3.1.3 Calculate the expec
25、ted parallel resistance ( pR ) through the connector of interest using the following formula. nRR p EIA-364-112 Page 3 3.1.4 Consideration may be given to analyzing the data per the actual use case. The computations for Rpwould use the exact contact positions planned in the final application. Altern
26、ately, if other contacts in the product are identical to those used in the final application, then that data could also be utilized. 3.1.5 Use the following formula to calculate the expected parallel resistance standard deviation (sp), found by applying the central limit theorem. nnssRp3.1.6 Per the
27、 central limit theorem, assume the distribution of pR is normal. 3.1.7 Calculate the percentile of interest using pR and sp and normal probability according to the following formula. pp szRP +=993.1.8 The value of z comes from a z-table. For the 99th percentile, z = 2.326. For a more conservative ca
28、lculation, a t-table may be used rather than a z-table. When a t-table is used, the degrees of freedom equals n 1. 3.2 Method B, current rating of parallel circuits (Under development) 4 Details to be specified The following details shall be specified in the referencing document: 4.1 Analysis method
29、 to be used 4.2 End of life contact resistance data for each test sequence from a connector qualification test program such as EIA-364-1000 (see the annex(s) for an example) EIA-364-112 Page 4 5 Test documentation Documentation shall contain the details specified in clause 4, with any exceptions, an
30、d the following: 5.1 Title of test 5.2 Test equipment used, and date of last and next calibration 5.3 Results of the analysis (see the annex(s) for an example) 5.4 Name of operator and start/finish dates of test EIA-364-112 Page A-1 Annex A Method A, example central limit theorem parallel contact re
31、sistance (informative) The following data illustrates the method using data from a sample of 25 FB DIMM parts, divided into five groups and subjected to the following stress tests: A.1 Test sequences Table A.1 Test groups Test Group Test or Examination A B C D E 1 Low Level Contact Resistance 1,4,6
32、1,4,6,8 1,3,5,7 1,4,6,8,10 1,4,6,8 2 Durability 2 2 2 2 2 3 Temperature Life 3 4 Thermal Shock 3 5 Physical Shock 6 6 Random Vibration 4 7 Cyclic Temperature &Humidity 5 8 Reseating 5 7 9 7 9 Mixed Flowing Gas 5 10 Thermal Cycling 5 11 Thermal Disturbance 7 12 Temperature Life (Preconditioning) 3 3
33、Specimen quantity (pieces) 5 5 5 5 5 NOTES 1 Group C did not compete testing on all contacts. 2 The data included here is for those contacts on which testing was completed. EIA-364-112 Page A-2 A.2 Results The method produces the results given below for circuits using 4, 22, and 59 contacts in paral
34、lel. Table A.2 Test results Group Number of Data Points (Readings) R sRn (Number of contacts in parallel) pR sp99th%tile A 1200 7.4409 1.0617 4 1.86022 0.13272 2.16891 B 1200 7.7255 0.714 4 1.93136 0.08925 2.13895C 290 5.7362 0.4641 4 1.43406 0.05801 1.56900 D 1200 7.0192 0.5723 4 1.75479 0.07153 1.
35、92118E 1200 7.676 0.7201 4 1.91900 0.09001 2.12836 A 1200 7.4409 1.0617 22 0.33822 0.01029 0.36215B 1200 7.7255 0.714 22 0.35116 0.00692 0.36725 C 290 5.7362 0.4641 22 0.26074 0.00450 0.27120D 1200 7.0192 0.5723 22 0.31905 0.00555 0.33195 E 1200 7.676 0.7201 22 0.34891 0.00698 0.36514A 1200 7.4409 1
36、.0617 59 0.12612 0.00234 0.13157 B 1200 7.7255 0.714 59 0.13094 0.00158 0.13460C 290 5.7362 0.4641 59 0.09722 0.00102 0.09961 D 1200 7.0192 0.5723 59 0.11897 0.00126 0.12191E 1200 7.676 0.7201 59 0.13010 0.00159 0.13380 EIA-364-112 Page A-3 A.3 Validation A.3.1 A Monte Carlo simulation can validate
37、the results given above. The simulation method uses bootstrapped data points from the original raw data set with replacement. For a simulation meant to validate a 4-pin circuit, the simulation randomly selects 4 readings from a single stress group. The simulation calculates the parallel resistance o
38、f these 4 points and saves it. The simulation repeats this until 2,500 parallel resistances for the given pin count and stress group have been calculated. A.3.2 The Monte Carlo simulations produced the results given below. The percentile here is the actual percentile from the simulated parallel resi
39、stances, not a calculation based on the mean and standard deviation of those resistances. The is the difference between the prediction percentile given in the formulaic method above and the simulation percentile. Table A.3 Monte Carlo simulation results Group Simulations n pR sp99th%tile A 2500 4 1.
40、83133 0.12860 2.15800 0.01091B 2500 4 1.91569 0.08984 2.11717 0.02178C 2500 4 1.42808 0.05240 1.57970 -0.01070D 2500 4 1.74697 0.07120 1.91877 0.00241E 2500 4 1.90938 0.08609 2.13530 -0.00694A 2500 22 0.33213 0.00951 0.35617 0.00598B 2500 22 0.34803 0.00707 0.36431 0.00294C 2500 22 0.25931 0.00403 0
41、.26997 0.00123D 2500 22 0.31711 0.00542 0.32952 0.00243E 2500 22 0.34621 0.00643 0.36226 0.00288A 2500 59 0.12373 0.00213 0.12894 0.00263B 2500 59 0.12983 0.00157 0.13336 0.00125C 2500 59 0.09666 0.00080 0.09866 0.00095D 2500 59 0.11820 0.00122 0.12094 0.00096E 2500 59 0.12905 0.00145 0.13260 0.0012
42、0EIA-364-112 Page A-4 A.4 Histogram results The charts below graphically depict the results. The histograms represent the data for each group and pin count. The red lines represent the calculated limit from the prediction percentile. The blue lines represent the actual percentile from the simulation
43、s. Table A.4 Histogram results Group Raw n = 4 n = 22 n = 59 A 50100150200250Count.117 .119 .121 .123 .125 .127 .129 .131501001502001.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3100200300.31 .32 .33 .34 .35 .36 .37501001502006 7 8 9 10B 100200300.32 .33 .34 .35 .36 .37100200300Count.124 .126 .128 .13 .132 .13410
44、02003001.7 1.8 1.9 2 2.1 2.2501001502006 7 8 9C 100200300Count.094 .095 .096 .097 .098 .099 .11002003004001.3 1.4 1.5 1.6 1.750100150200250.25 .26 .272550751005 6 7 8 9D 50100150200Count.115.116.117 .118.119 .12 .121.122.1231002003001.6 1.7 1.8 1.9 2100200300.3 .31 .32 .33501001502005.5 6 6.5 7 7.5
45、8 8.5 9E 1002003006 7 8 9 10 111002003001.7 1.8 1.9 2 2.1 2.2 2.3100200300400.33 .34 .35 .36 .37100200300400Count.125 .127 .129.13 .131 .133NOTE The method was replicated at two other manufacturers with comparable results. A.5 Discussion A.5.1 The method used here begins with the common formula to c
46、alculate individual parallel resistance values, Rp. It is typically used to find the total resistance across n resistors in parallel or, in the case of this paper, n contacts used in the particular parallel circuit. =niipRR111EIA-364-112 Page A-5 A.5.2 The form for calculating the expected value of
47、the distribution of m of these parallel resistances is below. In the case of this paper, this distribution is of m connectors. 1mRRmjpjp= or substituting =mjjniipRmR11111. A.5.3 This form could be custom programmed into a script, though the approximation of its value as 1/n that of the arithmetic me
48、an of the end-of-life resistances is close enough for this application and doesnt require any custom scripting or programming. Therefore we use the simpler version. nRR p A.5.4 The form for calculating the variance of the distribution of Rp is: 1)(122=mRRsmjppjpor substituting 111111121112=mRmRsmjmj
49、jniijniip. EIA-364-112 Page A-6 A.5.5 One attribute that the method leverages is that the Central Limit Theorem applies to pR the same as it would to R . Evidence that this is true comes from the Monte Carlo simulation used to validate the formulae. As the number of contacts in the circuit increases, the distribution of the parallel resistance means becomes more and more normal. Table A.5 Distribution of parallel resistance means results Group Raw n = 4 n = 22 n = 59 A 5010
