Technical Library | 2010-03-23 11:50:22.0
This document discuss how to design SMT stencil base on IPC-7525. Introduction: PCBA (Printed Circuit Board Assembly) is a segment of printed circuit board technology. This segment of printed circuit board industry is concentrated in assemble all the pieces of electronic industry to one piece before output them to market. This segment covers: interconnection technology, package design technology, system integration technology, board and system test technology
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.
Technical Library | 2013-12-05 17:09:03.0
The functionality of electronic devices continues to increase at an extraordinary rate. Simultaneously consumers are expecting even more and in ever smaller packages. One enabler for shrinking electronics has been the flexible circuit board that allows the circuit board to fit a wide variety of shapes. Flexible printed circuits (FPC) have the capability to be very thin and can have unpackaged components directly attached using surface mount technology (SMT) and flip chip on flex technologies. Bare die can also be thinned and attached very close to the circuit board. However one caveat of high density flexible circuit boards with thin die is that they can be very fragile. The use of back side films and underfill can protect the die making circuits more robust. For underfill to work well it requires good adhesion to the circuit board which can mean that flux residues under the die normally must be removed prior to underfilling.
Technical Library | 2021-12-16 01:52:32.0
Package on Packages (PoP) find use in applications that require high performance with increased memory density. One of the greatest benefits of PoP technology is the elimination of the expensive and challenging task of routing high-speed memory lines from under the processor chip out to memory chip in separate packages. Instead, the memory sits on top of the processor and the connections are automatically made during assembly. For this reason PoP technology has gained wide acceptance in cell phones and other mobile applications. PoP technology can be assembled using one-pass and two-pass assembly processes. In the one-pass technique the processor is first mounted to the board, the memory is mounted to the processor and the finished board is then run through the reflow oven in a single pass. The two-pass technique has an intermediate step in which the memory is first mounted onto the processor.
Technical Library | 2008-01-16 18:25:55.0
The consumer's interest for smaller, lighter and higher performance electronics products has increased the use of ultra fine pitch packages, such as Flip Chips and Chip Scale Packages, in printed circuit board (PCB) assembly. The assembly processes for these ultra fine pitch packages are extremely complex and each step in the assembly process influences the assembly yield and reliability.
Technical Library | 2016-11-30 21:30:50.0
Mid-chip solder balling is a defect typically associated with solder paste exhibiting poor hot slump and/or insufficient wetting during the reflow soldering process, resulting in paste flowing under the component or onto the solder resist. Once molten, this solder is compressed and forced to the side of the component, causing mid-chip solder balling.This paper documents the experimental work performed to further understand the impact on mid-chip solder balling from both the manufacturing process and the flux chemistry.
Technical Library | 2021-11-03 16:49:59.0
Ultrathin bare die chips were soldered using a novel soldering technology. Using homogeneous flash light generated by high-power xenon flash lamp the dummy components and the bare die NFC chips were successfully soldered to copper tracks on polyimide (PI) and polyethylene terephthalate (PET) flex foils by using industry standard Sn-Ag-Cu lead free alloys. Due to the selectivity of light absorption, a limited temperature increase was observed in the PET substrates while the chip and copper tracks were rapidly heated to a temperatures above the solder melting temperature. This allowed to successfully soldered components onto the delicate polyethylene foil substrates using lead-free alloys with liquidus temperatures above 200 °C. It was shown that by preheating components above the decomposition temperature of solder paste flux with a set of short low intensity pulses the processing window could be significantly extended compared to the process with direct illumination of chips with high intensity flash pulse. Furthermore, it was demonstrated that with localized tuning of pulse intensity components having different heat capacity could be simultaneously soldered using a single flash pulse.
Technical Library | 2015-09-23 22:08:32.0
A molded interconnect device (MID) is an injection molded thermoplastic substrate which incorporates a conductive circuit pattern and integrates both mechanical and electrical functions. (...) Flip chip bonding of bare die on MID can be employed to fully utilize MID’s advantage in device miniaturization. Compared to the traditional soldering process, thermo-compression bonding with gold stud bumps provides a clear advantage in its fine pitch capability. However, challenges also exist. Few studies have been made on thermocompression bonding on MID substrate, accordingly little information is available on process optimization, material compatibility and bonding reliability. Unlike solder reflow, there is no solder involved and no “self-alignment,” therefore the thermo-compression bonding process is significantly more dependent on the capability of the machine for chip assembly alignment.
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.
Technical Library | 2008-08-28 22:50:11.0
The increasing use of lead-free solder has introduced a new set of process parameters when setting up wave solder equipment for effective soldering. Determining the proper flow characteristics of the solder wave for adequate hole fill is an essential step in achieving a reliable process. A variety of solder waves exist in the industry; each with advantages and disadvantages when performing lead-free wave soldering. One way to ensure adequate hole-fill is by increasing contact time at the Chip Wave.
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