Technical Library | 2010-12-16 16:59:09.0
This report discusses the significance of heat management in the design of printed circuit boards (PCB). After an introduction into the basics of PCBs the crucial mechanisms of heat transfer are discussed with regard to significance and typical design par
Technical Library | 1999-05-06 10:36:37.0
Augmented-Fin Air-Cooled Heat Sinks Achieve Higher Performance without Significant Rise in Static Pressure Drop.
Technical Library | 1999-05-06 10:46:06.0
Pentium-class portables present significant packaging problems. The heat generated inside a notebook not only reduces microprocessor reliability, but the reliability of peripheries such as hard drives and video chips. Although the processor is the primary heat-generating source, it isn’t always the component least tolerant of temperature...
Technical Library | 1999-05-06 11:18:25.0
The trend toward surface-mount assembly processes is making ball-grid array (BGA) packaging a popular choice for many types of devices, forcing designers to re-examine cooling of these large packages. While devices in BGAs transfer more heat to the board than leaded devices, the style of BGA packages has a large influence on the ability to transfer heat through other pathways, such as a top-mounted heat sink. Physical characteristics of the BGA further constrain the thermal designer. It takes forethought in board design to successfully accommodate devices that require significant heat dissipation. Multiple solutions exist, however, for BGA packages of all types.
Technical Library | 2007-09-06 11:03:33.0
EFD Inc. and Leister USA have collaborated to bust the myth that you cannot perform laser reflow with solder paste. Using Leister diode lasers, EFD has formulated solder pastes that survive the rapid reflow cycle typical of laser heating. These solder pastes reflow and wet well, without spatter, even when heating is accomplished in less than half a second. The flux core in wire solders cannot boast such flux spatter resistance in such an aggressive heating environment.
Technical Library | 2010-01-06 22:27:03.0
Increased functionality and performance requirements for microprocessors and ASICs have resulted in a trend to package these devices in the flip-chip BGA form factor (FCBGA). Because these devices use in excess of 40-100 Watts of power, their packages must dissipate heat in an extremely efficient manner. Most semiconductor companies have developed some type of thermally enhanced FCBGA package that provides heat dissipation through the back of the die to a heat spreader.
Technical Library | 2024-07-24 00:51:44.0
A blade server system (BSS) utilizes voltage regulator modules (VRMs), in the form of quad flat no-lead (QFN) devices, to provide power distribution to various components on the system board. Depending on the power requirements of the circuit, these VRMs can be mounted as single devices or banked together. In addition, the power density of the VRM can be high enough to warrant heat dissipation through the use of a heat sink. Typically, at field conditions (FCs), the BSS are powered on and off up to four times per day, with their ambient temperature cycling between 258C and 808C. This cyclical temperature gradient drives inelastic strain in the solder joints due to the coefficient of thermal expansion (CTE) mismatch between the QFN and the circuit card. In addition, the heat sink, coupled with the QFN and the circuit card, can induce additional inelastic solder joint strain, resulting in early solder joint fatigue failure. To understand the effect of the heat sink mounting, a FEM (finite element model of four QFNs mounted to a BSS circuit card was developed. The model was exercised to calculate the maximum strain energy in a critical joint due to cyclic strain, and the results were compared for a QFN with and without a heat sink. It was determined that the presence of the heat sink did contribute to higher strain energy and therefore could lead to earlier joint failure. Although the presence of the heat sink is required, careful design of the mounting should be employed to provide lateral slip, essentially decoupling the heat sink from the QFN joint strain. Details of the modeling and results, along with DIC (digital image correlation) measurements of heat sink lateral slip, are presented.
Technical Library | 2019-10-03 14:27:01.0
Knowing how package warpage changes over temperature is a critical variable in order to assemble reliable surface mount attached technology. Component and component or component and board surfaces must stay relatively flat with one another or surface mount defects, such as head-in-pillow, open joints, bridged joints, stretched joints, etc. may occur. Initial package flatness can be affected by numerous aspects of the component manufacturing and design. However, change in shape over temperature is primarily driven by CTE mismatch between the different materials in the package. Thus material CTE is a critical factor in package design. When analyzing or modeling package warpage, one may assume that the package receives heat evenly on all sides, when in production this may not be the case. Thus, in order to understand how temperature uniformity can affect the warpage of a package, a case study of package warpage versus different heating spreads is performed.Packages used in the case study have larger form factors, so that the effect of non-uniformity can be more readily quantified within each package. Small and thin packages are less prone to issues with package temperature variation, due to the ability for the heat to conduct through the package material and make up for uneven sources of heat. Multiple packages and multiple package form factors are measured for warpage via a shadow moiré technique while being heated and cooled through reflow profiles matching real world production conditions. Heating of the package is adjusted to compare an evenly heated package to one that is heated unevenly and has poor temperature uniformity between package surfaces. The warpage is measured dynamically as the package is heated and cooled. Conclusions are drawn as to how the role of uneven temperature spread affects the package warpage.
Technical Library | 1999-07-21 09:06:19.0
Thermal management is a growing challenge in the electronics industry. As the overall size of electronic devices grows smaller, the enclosed electronic assemblies operate at higher frequencies and generate more heat.
Technical Library | 2007-04-04 11:43:41.0
The present work offers a discussion and a first case study to identify and illustrate voiding mechanisms for a particular TIM between a heat spreader and the back of a flip chip. Pronounced differences were observed between stencil printing and dispensing in terms of initial void formation, apparently related to the specific properties of the material. Measurements of the effects of heat ramp rate and peak temperature showed the subsequent evolution and final void size distribution to be determined by the initial part of the cure profile up to the material gelling temperature.
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