1、 STD-BSI BS EN hOOb-2-48-ENGL 2000 m lb24bb 082934l 749 BS EN 60068-2-48:2000 IEC 60068-2-48: 1982 BRITISH STANDARD Environmental testing - Part 2: Tests - Guidance on the application of the tests of IEC 60068 to simulate the effects of storage The European Standard EN 60068-2-48:1999 has the status
2、 of a British Standard ICs 19.040 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW STD.BSI BS EN bOOb8-2-4-ENGL 2000 M lib24bb9 0829142 b85 = BS EN 60068-2-482000 Amd. No. Date This British Standard is the official English language version of EN 60068-2481999. It is identical w
3、ith IEC 60068248 1982. It supersedes BS 201 1-4.2: 1984 which is withdram Comments The UK participation in its preparation was entrusted to Technical Committee GEIJ104, Environmental conditions, classifcation and testllig, which has the responsibility to: - aid enquirers to understand the tea - pres
4、ent to the responsible intemationaVEuropean committee any enquiries on the interpretaion, or proposals for change, and keep the UK interests infonned; - rclititwL LcLi, in this case, the product may be subjected to particularly severe environmental stresses due to operation of the surrounding plant,
5、 or c) in installations which take a long time to complete, where the initial environment may be much more severe than the operational environment, e.g. large telephone switching offices, large computer installations, power stations, etc. NOTE - Reference should be made to specialized standards for
6、environmental data relative to these conditions. 2 Definition and object of a “storage test“ A “storage test“ is intended to simulate the effects of one or more environmental stresses acting on products during their normal storage life, and when the assumption of fatigue accumulation is likely, to e
7、stablish whether: a) storage prevents the use of the product in its intended application, for example the solderability characteristics of component leads or printed circuit boards are worsened, the drift of electrical parameters is excessive, open circuits or short circuits are caused, or b) signif
8、icant performance and/or reliability degradation occurs for products operated after storage, or c) for emergency equipment, the ability of products to function correctly and reliably is not impaired after prolonged non-operation. NOTE - For the reliability determination of relatively new products or
9、 those stored for long periods, and for the determination of functioning reliability after storage, reference should be made to the IEC standards dealing with reliability and maintainability. 3 Examples of degradation mechanisms and of failure types under storage conditions The following are typical
10、 examples of failure mechanisms and failure types occurring as a result of storage: 3.1 Component leads and printed circuit board solderability can be degraded due to oxidation or diffusion processes between base material and overplating. These processes are accelerated by heat, resulting in the for
11、mation of surfaces with greatly reduced solderability. Humid corrosion phenomena, perhaps accelerated by polluting substances in the atmosphere, may also be active. O BSI 03-2000 Page 4 3.2 Other examples of failure mechanisms due to humidity changes are: EN 6068-2-48:1999 3.2.1 Prolonged action of
12、very low humidity, even at relatively low temperatures, can produce a considerable drying of plastics; electrical and mechanical properties of these materials can be degraded with consequent damage or failure during operation after storage. 3.2.2 A high humidity during storage can be more dangerous
13、than it will be during operation, due to the absence of any self-heating effect. Prolonged storage at relative humidity levels lower than 80 % can also adversely influence functional characteristics and reliability of the stored products. 3.2.3 The internal humidity of imperfectly sealed containers
14、can progressively increase when stored under conditions of high relative humidity with high repetitive peak values, or cyc!iy tempratiiv on ?i mndorsitely hlqh re!?!ve !?vmld!y. Cenceqsen!y, ?!ter a long storage time, condensation can occur inside the container due to a sudden limited tempera tu re
15、decrease. 3.2.4 Products stored under conditions of high relative humidity and temperature can be affected by mould growth, especially if organic materials are present. These conditions also accelerate the effects of chemical action such as salt mist and industrial gases. 3.3 Other examples of failu
16、re mechanisms are: 3.3.1 Prolonged exposure in a high temperature environment can cause the drying of electrolytic capacitors and of batteries; loss of rigidity in thermoplastics; softening and creeping of protective compounds and of impregnating waxes. Generally, the ageing of materials is accelera
17、ted under these conditions. 3.3.2 Prolonged exposure in a low temperature environment can produce brittleness, cracking and breaking not only of rubber and plastics but also of metallic parts. Some seals can be degraded by shrinking or cracking. 3.4 Blocking (seizing) of mechanical parts due to high
18、 temperature oxidation or to humid corrosion. 3.5 The functional parameters of products may drift beyond specified limits. Open circuits or short circuits may occur. 4 Choice of the applicable test It is obviously not possible to define a single storage test as different parameters produce different
19、 stresses which may result in different types of deterioration or modes of failure. The standard tests described in IEC 60068 may be conveniently used for the simulation of specific storage conditions. Usually storage tests are based upon Tests A: Cold; B: Dry heat; and Ca: Damp heat, steady state.
20、The test duration is generally long, possibly up to several months (the maximum period for Test Ca is given as two months). Other tests can be more significant for some cases (e.g. salt mist, industrial atmosphere) and they should be considered during the preparation of a detailed storage specificat
21、ion. O BSI 03-2000 STDaBSI BS EN bOOb8-2-48-ENGL 2000 = lb24bb9 0829147 lb7 Page 5 It is recognized that standard tests are not intended to simulate actual conditions and it may be necessary to perform special tests in some circumstances. However, technical and economic considerations suggest that s
22、tandard tests should be used wherever possible. EN 60068-2-48:1999 In the choice of the applicable test, the writer of the relevant specification should take into consideration: a) the required object: see clause 2; b) the degradation mechanism and failure modes to be expected: these may be known fr
23、om previous experience or from an analysis of the characteristics of the product and of the storage conditions, related to the interactions between environment and materials: see clause 3; c) the significant environmental stresses involved and whether they can be considered as acting individually, i
24、n combination or in sequence; d) the possibility of accelerating the degradation mechanisms, without substantially altering the failure modes or introducing new ones. 4.1 Reference should be made to the Guidance documents applicable to the test methods of IEC 60068. Some considerations are given her
25、e regarding special criteria to be followed in the choice of test severities, taking account of the object of a storage test. 4.2 A test acceleration, useful in order to reduce the test duration, cannot always be obtained with a stress increase because important changes of the degradation mechanisms
26、 can arise, giving results which have no practical usefulness. Such a consideration applies for example to: a) humid corrosion phenomena, with or without the action of atmospheric pollutants: increasing the relative humidity results in corrosion products which morphologically are totally different f
27、rom those formed in natural conditions; b) consequences of water vapour absorption by insulating materials, especially those related to the irreversible effects due to structural changes: humidity conditions less stringent than those specified in Test Ca of IEC 60068-2-3 with lower temperature and/o
28、r lower relative humidity may be appropriate, particularly when analysing the effects on poorly protected products; c) slow deformation phenomena in some materials, so important for the parameter drift in electronic components: under natural conditions, such phenomena are often very different from t
29、hose produced by rapid changes of temperatures over an extended range. 4.3 In some cases, the storage test may last a long time. The usefulness of the test is then due not to the reduction in time needed to obtain results, but to the fact that the phenomena occur under controlled and reproducible co
30、nditions. Generally, for these tests with limited stress acting for a long time, greater changes of test conditions can be tolerated than for highly accelerated tests. Test equipment control and regulation is therefore simplified. 4.4 In other cases, the test can be accelerated by an increase of the
31、 stress without substantially changing the deterioration mechanisms, for example: a) a test temperature increase can accelerate the drying, for example, of electrolytic capacitors and of batteries and in general all the ageing processes of materials exposed to dry heat; b) brittleness, cracking and
32、breaking of rubber, plastics and also some metallic parts, caused by low temperatures, can be accelerated by exposure to temperatures suitably lower than those of the actual storage conditions. 0 BSI 03-2000 Page 6 5 Test procedure details EN 868-2-48:1YYY Storage tests as such do not require more a
33、ttention than tests applied for other purposes (determination of characteristics, qualification, etc.). The normal precautions taken when carrying out tests, especially those related to the control of test equipment and associated instrumentation, are applicable to storage tests. Special care should
34、 be taken in the measurement of functional parameters particularly during and after very long duration tests. Recovery conditions following the test will often be important. For instance, dehydrated materials may start to absorb moisture, or materials which have absorbed or adsorbed moisture may sta
35、rt to dry out. In such cases the recovery conditions should be clearly defined and closely controlled, :ufv:u:c2 keir!:n, !z:udc tv fhc tzsts i: !EC vccvv-2. NOTE - Controlled recovery conditions are defined in 5.4.1 of IEC 60068-1. O BSI 03-2000 STDmBSI BS EN bOObB-2-4B-ENGL 2000 Lb24bb9 0829149 T3
36、T Page 7 EN 60068-2-48:1999 Annex ZA (normative) Normative references to international publications with their corresponding European publications This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the approp
37、riate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publica
38、tion referred to applies (including amendments). NOTE: When an international publication has been modified by common modifications, indicated by (mod), the relevant ENIHD applies. Year Publication - Year Title EN/HD - IEC 60068-1 Basic environmental testing procedures EN 60068-1 Part 1: General and
39、guidance IEC 60068-2-1 Part 2: Tests - Tests A: Cold EN 60068-2-1 IEC 60068-2-2 1974 Part 2: Tests - Test B: Dry heat EN 60068-2-2” 1993 IEC 60068-2-3 1969 Part 2: Tests - Test Ca: Damp heat, steady HD 323.2.3 C2” 1987 state 1) EN 60068-2-2 includes supplement A: 1976 to IEC 60068-2-2. 21 HD 323.2.3
40、 SZ includes A1:1984 to IEC 60068-2-3. BS EN 60068-2-48:2000 IEC O6&2-48:1982 BSI 389 ChiswickHigh Road London w4 4AL STD.BSI BS EN bOOb-2-4-ENGL 2000 Lb24bb 082LSO 75L BSI is the independent national body responsible for preparing British Standards. It . presents the UK view on standards in Europe
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