Cooling techniques for electronic equipment

Book•

Cooling techniques for electronic equipment

07 Nov 1980-

TL;DR: In this article, the authors present practical guides for Natural Convection and Radiation Cooling for Electronic Components. But they do not consider the effects of thermal stresses in lead wires, Solder Joints and Plated Throughholes.

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Abstract: Evaluating the Cooling Requirements. Designing the Electronic Chassis. Conduction Cooling for Chassis and Circuit Boards. Mounting and Cooling Techniques for Electronic Components. Practical Guides for Natural Convection and Radiation Cooling. Forced--Air Cooling for Electronics. Thermal Stresses in Lead Wires, Solder Joints, and Plated Throughholes. Predicting the Fatigue Life in Thermal Cycling and Vibration Environment. Transient Cooling for Electronic Systems. Special Applications for Tough Cooling Jobs. Effective Cooling for Large Racks and Cabinets. Finite Element Methods for Mathematical Modeling. Environmental Stress Screening Techniques. References. Index.

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Journal Article•DOI•

Sensitivity of circuit peak thermal performance to convective and geometric variation

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K. Azar¹, S.E. Develle, Vincent P. Manno•Institutions (1)

Bell Labs¹

01 Dec 1989-IEEE Transactions on Components, Hybrids, and Manufacturing Technology

TL;DR: In this article, a prototype electronic device consisting of two boards with multiple power dissipating components in a vented enclosure is studied for its thermal performance under forced and natural air cooling conditions.

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Abstract: A prototype electronic device consisting of two boards with multiple power dissipating components in a vented enclosure is studied for its thermal performance under forced and natural air cooling conditions. The internal geometry and physical orientation are also varied. Results in terms of effective board thermal resistances and local heat-transfer coefficients are reported. Forced convective resistances were a factor of five smaller than natural convection values. Physical orientation is seen to be the second most important sensitivity after convection mode due to the potential for local buoyancy effects. Overall thermal performance can be affected by as much as 25% due to non-convection-mode-related variations. Design implications as well as the applicability of the data to analysis method validation are discussed. >

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4 citations

Accelerated Life Testing of Electronic Circuit Boards with Applications in Lead-Free Design

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Joseph Moses Juarez

01 Jan 2012

TL;DR: In this paper, the authors present methods for addressing problems that currently can only adequately be solved using Quality Reliability Engineering (QRE) approaches especially for accelerated life testing of electronic printed wiring boards with applications to avionics.

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Abstract: This dissertation presents methods for addressing research problems that currently can only adequately be solved using Quality Reliability Engineering (QRE) approaches especially accelerated life testing (ALT) of electronic printed wiring boards with applications to avionics circuit boards. The methods presented in this research are generally applicable to circuit boards, but the data generated and their analysis is for high performance avionics. Avionics equipment typically requires 20 years expected life by aircraft equipment manufacturers and therefore ALT is the only practical way of performing life test estimates. Both thermal and vibration ALT induced failure are performed and analyzed to resolve industry questions relating to the introduction of lead-free solder product and processes into high reliability avionics. In chapter 2, thermal ALT using an industry standard failure machine implementing Interconnect Stress Test (IST) that simulates circuit board life data is compared to real production failure data by likelihood ratio tests to arrive at a mechanical theory. This mechanical theory results in a statistically equivalent energy bound such that failure distributions below a specific energy level are considered to be from the same distribution thus allowing testers to quantify parameter setting in IST prior to life testing. In chapter 3, vibration ALT comparing tin-lead and lead-free circuit board solder designs involves the use of the likelihood ratio (LR) test to assess both complete failure data and S-N curves to present methods for analyzing data. Failure data is analyzed using Regression and two-way analysis of variance (ANOVA) and reconciled with the LR test results that indicating that a costly aging pre-process may be eliminated in certain cases. In chapter 4, vibration ALT for side-by-side tin-lead and lead-free solder black box designs are life tested. Commercial models from strain data do not exist at the low levels associated with life testing and need to be developed because testing performed and presented here indicate that both tin-lead and lead-free solders are similar. In addition, earlier failures due to vibration like connector failure modes will occur before solder interconnect failures.

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4 citations

Cites methods from "Cooling techniques for electronic e..."

...This dissertation will not address these thermal ALT methods; computer codes exist to perform these 8 analyses for solder joint component failure like those of Clech (2008) and CALCE (2011), and the books by Lau (1994) and Steinberg (1991) show how to predict solder joint failures....
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...In addition, S-N curve development and how it is incorporated into analysis for predicting life is presented using Steinberg (2000) equations....
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...Calculating the CDI denominators, the Ni represent the 1, 2, and 3 Sigma levels of rms stress and are computed using the following equation Ni = N (S/Si)(4) (13) where N = 20 x 10(6) cycles, and S is computed by an equation representing 3sigma stresses for components expected to achieve a fatigue life of about 20 million stress reversals in a random vibration environment per the research published by Steinberg (2000) Si = PWB rms stress responses from the measured strains....
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...This section also describes how to calculate life given solder joint stress or displacements based on Steinberg (2000). Life using stress is calculated as follows and is called the cumulative damage index (CDI):...
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...19, N = 1000 cycles-to-failure, S = 6500 psi, and exponent = 4 using Steinberg’s (2000) for tin-lead solder. Therefore, NSnPb = 1.8 million predicted cycles-to-failure for Sn-Pb solder, but the actual GG CCA had only between 456,000 to 649,000 cycles (Table 4.5) and thus did not expect failure of this GG CCA. The following calculation shows why the CALCE PWA code is conservative for lead-free LRU applications, applying equation (14): Ni = N x (Z / Zi), where N = 20 x 10(6) cycles, and Z is computed by an equation representing 3 sigma displacements for components expected to achieve a fatigue life of about 20 million stress reversals in a random vibration environment per the research published by Steinberg (2000). Zi = 0....
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Patent•

Method and apparatus for predicting steady state temperature of solid state devices

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William P. Sturner¹, Ming T. Shih¹•Institutions (1)

Lockheed Martin Corporation¹

26 Jul 2007

TL;DR: In this paper, a thermocouple is used to detect the temperature of a solid state system, and a processor is programmed with instructions to construct an initial curve for the system, the initial curve having a shape; obtain a plurality of theoretical temperature curves for the solid-state system; select one of the plurality of temperature curves having the shape closest to the shape of the original curve; and superimpose the selected theoretical temperature curve on the initial shape to predict the steady state temperature.

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Abstract: The disclosure generally relates to method and apparatus for predicting the steady state temperature of solid state devices, preferably under transient conditions. An apparatus according to one embodiment of the disclosure includes a thermocouple for detecting temperature of the solid state system; a processor in communication with the thermocouple and programmed with instructions to: construct an initial curve for the solid state system, the initial curve having a shape; obtain a plurality of theoretical temperature curves for the solid state system; select one of the plurality of theoretical temperature curves having a shape closest to the shape of the initial curve; and superimposing the selected theoretical temperature curve on the initial curve to predict the steady state temperature.

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4 citations

Proceedings Article•DOI•

The application of transient thermal analysis in solder joint thermal fatigue life analysis

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Xianglei Kong, Fengming Lu, Weili Li

18 Dec 2014

TL;DR: In this article, a method of solder joint thermal fatigue life analysis using transient thermal analysis is introduced, and also a case study of temperature shock test to an CPU module is presented.

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Abstract: In this paper, a method of solder joint thermal fatigue life analysis using transient thermal analysis is introduced, and also a case study of temperature shock test to an CPU module. The results show that this method obtained the temperature load under actual use, which is closer to engineering problems. The module's maximum temperature variation range is 50D-132D. Under the temperature load, the maximum stress of solder joint is 42.8MPa and its thermal fatigue life is 6376 cycles.

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4 citations

Journal Article•DOI•

Momentum and heat transfer from a semi-circular cylinder in Bingham plastic fluids

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Anurag Kumar Tiwari¹, R.P. Chhabra¹•Institutions (1)

Indian Institute of Technology Kanpur¹

15 Nov 2015-Applied Mathematical Modelling

TL;DR: In this article, momentum and heat transfer from a semi-circular cylinder immersed in Bingham plastic fluids have been investigated numerically in the laminar flow regime, and the results on the size and shape of yielded/unyielded zones, drag coefficient and Nusselt number are presented and discussed.

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4 citations

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Cooling techniques for electronic equipment

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