Technical Library: cte mismatch (Page 1 of 7)

Throughput vs. Wet-Out Area Study for Package on Package (PoP) Underfill Dispensing

Technical Library | 2012-12-17 22:05:22.0

Package on Package (PoP) has become a relatively common component being used in mobile electronics as it allows for saving space in the board layout due to the 3D package layout. To insure device reliability through drop tests and thermal cycling as well as for protecting proprietary programming of the device either one or both interconnect layers are typically underfilled. When underfill is applied to a PoP, or any component for that matter, there is a requirement that the board layout is such that there is room for an underfill reservoir so that the underfill material does not come in contact with surrounding components. The preferred method to dispensing the underfill material is through a jetting process that minimizes the wet out area of the fluid reservoir compared to traditional needle dispensing. To further minimize the wet out area multiple passes are used so that the material required to underfill the component is not dispensed at once requiring a greater wet out area. Dispensing the underfill material in multiple passes is an effective way to reduce the wet out area and decrease the distance that surrounding components can be placed, however, this comes with a process compromise of additional processing time in the underfill dispenser. The purpose of this paper is to provide insight to the inverse relationship that exists between the wet out area of the underfill reservoir and the production time for the underfill process.

Nordson ASYMTEK

Dam and Fill Encapsulation for Microelectronic Packages

Technical Library | 1999-08-27 09:29:49.0

Contract packaging houses have to contend with a large mix of die types and products. Flexibility and quick turnaround of package types is a must in this industry. Traditional methods of die encapsulation, (i.e., use of transfer-molding techniques), are only cost effective when producing a large number of components. Liquid encapsulants now provide similar levels of reliability1, and are cost effective...

Nordson ASYMTEK

Reflow Soldering Processes and Troubleshooting: SMT, BGA, CSP and Flip Chip Technologies

Technical Library | 2021-01-03 19:24:52.0

Reflow soldering is the primary method for interconnecting surface mount technology (SMT) applications. Successful implementation of this process depends on whether a low defect rate can be achieved. In general, defects often can be attributed to causes rooted in all three aspects, including materials, processes, and designs. Troubleshooting of reflow soldering requires identification and elimination of root causes. Where correcting these causes may be beyond the reach of manufacturers, further optimizing the other relevant factors becomes the next best option in order to minimize the defect rate.

SMTnet

Rework Challenges for Smart Phones and Tablets

Technical Library | 2015-04-23 18:48:18.0

Smart phones are complex, costly devices and therefore need to be reworked correctly the first time. In order to meet the ever-growing demand for performance, the complexity of mobile devices has increased immensely, with more than a 70% greater number of packages now found inside of them than just a few years ago. For instance, 1080P HD camera and video capabilities are now available on most high end smart phones or tablet computers, making their production more elaborate and expensive. The printed circuit boards for these devices are no longer considered disposable goods, and their bill of materials start from $150.00, with higher end smart phones going up to $238.00, and tablets well over $300.00.

Metcal

Flip Chip Attach Techniques

Technical Library | 2019-05-21 17:38:55.0

Last month we presented Flip Chip Rework.As promised, this month we follow up with attachment techniques. Flip chip assembly is a key technology for advanced packaging of microelectronic circuits. It allows attachment of a bare chip to a packaging substrate in a face-down configuration, with electrical connections between the chip and substrate via conducting “bumps.” Flip chip technology was first invented by IBM for mainframe computer application in the early 1960s. Semiconductor devices are mounted face down and electrically and mechanically connected to a substrate (Figure 1). IBM called this manufacturing process a C4 process (controlled collapse chip connection).

ACI Technologies, Inc.

Temperature Cycling and Fatigue in Electronics

Technical Library | 2020-01-01 17:06:52.0

The majority of electronic failures occur due to thermally induced stresses and strains caused by excessive differences in coefficients of thermal expansion (CTE) across materials.CTE mismatches occur in both 1st and 2nd level interconnects in electronics assemblies. 1st level interconnects connect the die to a substrate. This substrate can be underfilled so there are both global and local CTE mismatches to consider. 2nd level interconnects connect the substrate, or package, to the printed circuit board (PCB). This would be considered a "board level" CTE mismatch. Several stress and strain mitigation techniques exist including the use of conformal coating.

DfR Solutions

Meeting Heat And CTE Challenges Of PCBs And ICs

Technical Library | 2008-11-13 00:06:32.0

The electronics industry is facing issues with hot spots, solder joint stresses and Coefficient of Thermal Expansion (CTE) mismatch between PCB and IC substrate. Flip chip type packages for example have very low CTE compared to traditional PCB material. Thus it is necessary to have low CTE printed circuit boards in order to keep solder joint intact with such low CTE packages. There are currently several materials available in the market to address thermal and CTE challenges but each material has its own advantages and limitations...

Stablcor

A Low Cost Manufacturing Solution - Low Temperature Super-Fast Cure and Flow Reworkable Underfill

Technical Library | 2016-01-12 11:09:47.0

In order to meet the increasing demand of device miniaturization, high speed, more memory, more function, low cost, and more flexibility in device design and manufacturing chain, underfilling has increasingly become an essential process for the good reliability of electronic devices. Filled capillary underfill has been selected for used in package-level where there is large thermal stress caused by CTE mismatch issue, but the underfill is usually not reworkable. Unfilled capillary underfill has been used for board-level application such as BGA/CSP, POP, WL-CSP where there is need for mechanical shock resistance, the underfill is usually reworkable.

YINCAE Advanced Materials, LLC.

A Novel Low Temperature Fast Flow And Fast Cure Reworkable Underfill

Technical Library | 2014-04-11 16:03:15.0

In order to meet the increasing demand of device miniaturization, high speed, more memory, more function, low cost, and more flexibility in device design and manufacturing chain, underfilling has increasingly become an essential process for the good reliability of electronic devices. Filled capillary underfill has been selected for use in package-level where there is large thermal stress caused by CTE mismatch issue, but the underfill is usually not reworkable. Unfilled capillary underfill has been used for board-level application such as BGA/CSP, POP, WL-CSP where there is need for mechanical shock resistance, the underfill is usually reworkable.

YINCAE Advanced Materials, LLC.

Effects of Package Warpage on Head-in-Pillow Defect

Technical Library | 2017-07-06 15:50:17.0

Head-in-pillow (HiP) is a BGA defect which happens when solder balls and paste can't contact well during reflow soldering. Package warpage was one of the major reasons for HiP formation. In this paper, package warpage was measured and simulated. It was found that the package warpage was sensitive to the thickness of inside chips. A FEM method considering viscoelastic property of mold compound was introduced to simulate package warpage. The CTE mismatch was found contributes to more than 90% of the package warpage value when reflowing at the peak temperature. A method was introduced to measure the warpage threshold, which is the smallest warpage value that may lead to HiP. The results in different atmospheres showed that the warpage threshold was 50μm larger in N2 than that in air, suggesting that under N2 atmosphere the process window for HiP defects was larger than that under air, which agreed with the experiments.

Samsung Electronics

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