ISSN:0748-8017    

DOI:10.1002/qre.4680040302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

ISSN:0748-8017    

DOI:10.1002/qre.4680040303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractPretinning of gold‐plated components is often done to avoid the formation of brittle Au/Sn intermetallic compounds, which may lower the mechanical strength of the joints. In this investigation the reliability of 32LCCs surface mounted on alumina boards is tested in internal and external temperature cycling, as well as in shear tests, and the effect of pretinning is studied. One thousand times of temperature cycling between −55 and +125°C and 2000 h of power cycling with an upper joint temperature of +75°C did not cause any electrical opens.Shear tests made after a 168 h heat treatment at +125°C and 1000 temperature cycles showed that forces of approximately 1000 N were required to break the chip carrier joints. The microstructure of Sn62/Pb36/Ag2 solder joints containing gold was examined and the existing phases were identified using electron diffraction X‐ray analysis. The joints fail at the Au/Sn intermetallics at the chip carrier metallization or at the Cu/Sn compounds formed at the substrate thick film/solder interface. No deterioration of the overall joint strength due to Au/Sn intermetallics was seen, when the gold content in the joints was approximately 4 weight

ISSN:0748-8017    

DOI:10.1002/qre.4680040304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe load‐strength theory is used to simulate the relations between the reliability, the safety factors used in the mechanical design and the different material conditions caused by batch variations in raw material, the injection moulding process and the mould desig

ISSN:0748-8017    

DOI:10.1002/qre.4680040305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractMIL‐HDBK‐217E is based on some major fallacies and oversimplifications. These include the assumption of constant failure rate, the assumed independence of the Pi factors, the oversimplification of temperature dependence, the neglect of process yield and screening fall‐out as determinants in the categorization of quality grade and the absence of manufacturing date information. These weaknesses are discussed and some recommendations

ISSN:0748-8017    

DOI:10.1002/qre.4680040306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractProbability goals are commonly used in conjunction with Poisson‐distributed variability to estimate initial pipeline spares requirements for aircraft organizations. An analysis of field data indicates that these deployment models may significantly underestimate spares acquisition quantities required in order to maintain probability goals throughout a system life cycle. This paper defines reliability of spare part stocks as the probability that these stocks will satisfy demands throughout a calendar time interval which begins at random points in the life cycle. Five models for spares planning were applied to field data from a small aircraft organization. The common goal in these analyses was based on military logistic standards: 0.99 probability for each part type over a replenishment interval of 360 h. Two initial interval (Poisson) models produced spares requirements averaging 273 units. The average for the three limiting (non‐Poisson) models was 3630 units. The limiting models also made it evident that spares must be purchased to refill the pipeline several times in a 20 year life cycle. It is concluded that a limiting buffer stock model is most realistic for planning normal spares requirements and that a renewal model should be used if the pipeline could be severed during surge periods of activ

ISSN:0748-8017    

DOI:10.1002/qre.4680040307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractA physical model describes device failure in terms of a series ofnmicroscopic events (such as defect creation) which are describable in terms of an identifiable activation energy. The results show a ‘Weibull like’ time dependence, but the temperature dependence is not of the simple Arrhenius form. Application is made to the ‘dark’ leakage current in a PIN photodiode and to the deviation in threshold voltage in a MOSFET. In particular the threshold voltage is shown to depend on a series of activated processes, and the required number of such processes to cause failure increases with the width of the gate el

ISSN:0748-8017    

DOI:10.1002/qre.4680040308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper reviews the present knowledge on subsurface burnout mechanisms in Gallium Arsenide (GaAs) electronic devices. The results of the work should assist in the creation of more reliable devices with greater radiation hardness.

ISSN:0748-8017    

DOI:10.1002/qre.4680040309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper examines the cause of ‘knees’ or ‘freaks’ in the life‐failure patterns resulting from some fatigue processes. A theory is developed which takes into account the extra fatigue damage associated with the non‐elastic behaviour of the material. It appears to account for the knee and agrees well qualitatively with test results, though quantitative comparisons are not possible because the stochastic data required for the calculation are not available. It is shown that ‘S’‐shaped curves sometimes experienced at higher loading roughness are also due to the same mechanism. The theory suggests that the undesirable features of the failure patterns, whose origin has not hitherto been fully investigated, can be eliminated by a design which is intrinsically reliable with respect to the elastic limit (or with respect to the yield strength if a small loss of reliability is acceptable). Because the knees or freaks appear to be a consequence of the fatigue process and arise with conventionally distributed mechanical properties it is suggested that this design action would be more effective than eliminating the items b

ISSN:0748-8017    

DOI:10.1002/qre.4680040310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThis is the first part of a three part article under the general heading of ‘Off the bathtub onto the roller‐coaster curve’, a short version1of which was presented at the 1988 Annual Reliability and Maintainability Symposium in U.S.A. The other two parts, to be published in later issues of this journal, are entitled ‘The roller‐coaster curve is in’ and ‘Physical basis for the roller‐coaster hazard rate curve’. This three‐part article provides detailed discussions of the findings leading to the conclusions on the roller‐coaster characteristics for the hazard rate curve for electronics. Part 1 being presented here covers the discussions on problems with the bathtub curve. The problems include making erroneous decisions resulting in reliability demonstration risks against the manufacturers, windfall profits for satellite manufacturers, false claims in reliability growth and reliability prediction accuracy and stress screening shortfalls. More important than the erroneous short‐term decisions is the long‐term reliability engineering methodology development. It is critical that we must reshape the course of reliability methodology development away from

ISSN:0748-8017    

DOI:10.1002/qre.4680040311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY