Technical Articles From ACI Technologies, Inc.
Read technical articles about electronics manufacturing added by ACI Technologies, Inc.
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63 technical articles added by ACI Technologies, Inc.
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A Non-destructive Approach to Identify Intermittent Failure Locations on Printed Circuit Cards (PCC) that have been Temperature Cycle Tested
Dec 07, 2020 | ACI Technologies, Inc.
Temperature cycling testing is a method of accelerated life testing done to PCCs that are exposed to normal operation temperature variations over its lifetime. During the testing, intermittent "open" failures can first occur at the hot and cold extremes of the test, exposing weaknesses in the design and assembly. A poor/weak solder joint fatigues, a via trace or barrel cracks, loose connections or a component fails all causing an intermittent open. When not at extreme temperatures, the PCC assembly relaxes, the "open" closes creating electrical connectivity. If you are monitoring the PCC under test in-situ you will know that an intermittent failure has occurred, and the test could be stopped for inspection. If in-situ monitoring was not implemented, you would not know if there were intermittent failures or not. The PCC gets powered up and works fine at room temperature....
Ball Grid Array (BGA) Voiding Affecting Functionality
Nov 09, 2020 | ACI Technologies, Inc.
A customer contacted ACI Technologies regarding a high failure rate of their assemblies. They provided assemblies to be X-rayed and inspected for the purpose of identifying any process related issues such as (but not limited to) solder and assembly workmanship and evidence of damage due to moisture related problems during reflow (a.k.a. "popcorning"). Moisture damage usually appears as physical damage to the component. The first indication of moisture damage would be externally observable changes to the package in the form of bulging or fractures to the outer surface of the component, an example of which is shown in Figure 1. Internally observable indicators of moisture damage typically include fractures to the die inside the package and lifted or fractured wire bonds. These conditions would be apparent during transmissive X-ray inspection. Another symptom of moisture related damage would be inconsistent solder joint sizes that result from package deformation during the liquidus phase of the reflow process. None of these indicators of moisture related damage were present on the customer samples....
Reworking ALD Coatings
Sep 02, 2020 | ACI Technologies, Inc.
Atomic layer deposition (ALD) is a process of creating coatings on a molecular layer by layer basis. Using an iterated sequence of self-saturating deposition cycles that are self-terminating, a single layer can be deposited at a time, allowing for highly uniform films with complete conformality. The composition of the film typically used for coating printed wiring boards (PWBs) is a high alumina (Al2O3) sequential deposition of alumina and titania capped with a corrosion protective titanium aluminate layer, most notably ALD-Cap from Sundew Technologies, LLC. Rework is a process of restoring an electronics assembly to full functionality to prolong equipment life and reduce the amount of scrap. The process typically involves:...
ALD of Alumina Ceramic Films for Hermetic Protection
Aug 05, 2020 | ACI Technologies, Inc.
A primary issue in electronics reliability for military applications is the ability to ensure long term operability in harsh, extreme environments. This requires more rigid standards, such as the MIL-STD-883 (Department of Defense Test Method Standard for Microcircuits), which commercial grade electronics typically do not satisfy. A solution commonly employed is to package the critical electronic components in hermetically sealed metal or ceramic enclosures which are costly and labor intensive. Not only are the components more expensive, but the assembly process is more difficult to automate, resulting in a substantial cost premium for military grade electronics....
Lead-Free Risk Mitigation -- A Case Study
Jul 01, 2020 | ACI Technologies, Inc.
A company approached ACI Technologies (ACI) for assistance with a new product that was about to undergo its initial proof-of-concept prototype build. This product was an item that was being furnished to the Department of Defense for a program designed to increase the technical capabilities of computer equipment issued to the war fighter. The requirements for this item specified the use of tin-lead solder during assembly of production units. One of the main responsibilities for ACI during this project was to assist the client in mitigating the risk introduced using commercial off-the-shelf materials that may be lead-free....
Lead-Free Control Plan
Jun 02, 2020 | ACI Technologies, Inc.
A commercial systems manufacturer working on a major defense program contacted the Helpline for urgent assistance with an issue of failed parts during reliability testing. They were attempting to incorporate commercial off-the-shelf (COTS) computer-related hardware into a battlefield system and were experiencing reliability issues. It was noted that the parts were labeled by the vendor as "compliant to military (or MIL) standards" but not clearly identified as tin-lead or lead-free. ACI Technologies has supported a number of customers with lead-free issues and we assisted the customer in developing a short term and long-term solution to their problem....
Pad Cratering
May 08, 2020 | ACI Technologies, Inc.
A customer contacted the Helpline to perform analysis on a lead-free assembly which exhibited intermittent functionality. The lead-free assembly exhibiting intermittent functionality when pressure was applied to the ball grid array (BGA) packages. Industrial adaptation of a Restriction of Hazardous Substances (RoHS) compliant solder standard has created a new host of failure modes observed in lead-free assemblies. Pad cratering occurs when fractures propagate along the epoxy resin layer on the underside of the BGA connecting pads. While originating from process, design, and end use conditions, it is the combination of a rigid lead-free solder with inflexible printed circuit board (PCB) laminates that has advanced the prevalence of this condition. Pad cratering is simply the result of mechanical stress exceeding material limitations....
Product Design and Early Manufacturing Involvement
Apr 01, 2020 | ACI Technologies, Inc.
It happens much too often; manufacturing engineers are brought into a NEW product design phase at the very end of a design and are asked to provide input that should have been provided much earlier. One needs to understand how the circuit board design and quality of the manufacturing process not only effects assembly yield and product reliability, but how it could also affect the results of any testing that is done to circuit packs during prototyping. It is important that any circuit pack (including prototypes) that will be used in reliability, performance and functional testing be designed with the proper features and assembled with a manufacturing process that has been developed to produce a high-quality assembly. If not, the results of any testing might not represent the actual characteristics of the design and provide miss-guidance to future changes....
Cleaning No-Clean Fluxes Prior to Conformal Coating
Mar 09, 2020 | ACI Technologies, Inc.
A customer called the Helpline seeking advice for cleaning no-clean fluxes prior to applying a conformal coating. The customer's assemblies were manufactured with a no-clean rosin based solder paste (ROL0) and were cleaned with an isopropyl alcohol (IPA) wash. After cleaning, a white residue was sometimes found in areas with high paste concentrations and was interfering with the adhesion of the conformal coating (Figure 1). For conformal coatings to adhere properly, the printed circuit board (PCB) surface must be clean of fluxes and other residues. In addition, ionic contamination left by flux residues can lead to corrosion and dendrite growth, two common causes of electronic opens and shorts. Other residues can lead to unwanted impedance and physical interference with moving parts....
Mechanical Drop Shock Testing
Feb 03, 2020 | ACI Technologies, Inc.
Accurate impact testing is a key component to establishing that a product is not only reliable, but durable in an end-use environment. ACI Technologies tested a high-g circuit board to demonstrate component durability and ruggedization for guided munitions. The Lansmont Model 23 Shock Test System customized with a Dual Mass Shock Amplifier was used for this testing (Figure 1)....
Atomic Layer Deposition
Jan 13, 2020 | ACI Technologies, Inc.
Is it possible to coat electronic assemblies with a thin, uniform in thickness, pinhole-free, moisture impervious, truly hermetic (by the MIL-STD-883 definition) film of ceramic material that is far more affordable than placing the same electronic assemblies in the currently used glass-to-metal sealed, thick, heavy, metal-and-ceramic-based hermetic enclosures? Since the coating (called a “conformal coating”) would be both hermetic (moisture proof) and hundreds or thousands of times thinner than the currently used enclosures, it would be both less expensive, lighter, and still just as effective in excluding moisture (hermetic) as the current heavy, bulky, expensive electronic enclosures are....
Masking for Conformal Coatings
Dec 05, 2019 | ACI Technologies
Conformal coatings are regularly employed to protect the surface of a soldered printed circuit board assembly from moisture, chemicals in the PCBA's service environment, and foreign objects or debris. Conformal coatings are nonconductive and therefore cannot be placed on any location where electrical contact will be required, such as connector pins, test points, and sockets. Conformal coatings are also not permitted on any mechanical interface location, such as mounting holes or brackets, to assure the proper fit between items in the final assembly. In order to apply conformal coatings to an assembly and comply with the restrictions on keep-out areas, masking is employed to protect those surfaces. ...
Fiber Optic Cabling
Nov 13, 2019 | ACI Technologies, Inc.
Fiber optic harnesses appear simple, but they have been designed to maintain all of the critical areas of aligning two fibers and minimize the losses associated with a break in the transmission path. In order to understand how the connectors overcome alignment issues, we must first understand the issues. Fiber optic communications networks use specific wavelengths of light (or colors) to transmit information through a clear fiber at high speed. They use the property of internal reflection along the fiber’s axis to contain the light and keep the optical power high enough to be detected at the receiving end. ...
Investigation of PCB Failure after SMT Manufacturing Process
Oct 21, 2019 | ACI Technologies, Inc.
An ACI Technologies customer inquired regarding printed circuit board(PCB) failures that were becoming increasingly prevalent after the SMT (surface mount technology) manufacturing process. The failures were detected by electrical testing, but were undetermined as to the location and specific devices causing the failures. The failures were suspected to be caused predominately in the BGA (ball grid array) devices located on specific sites on this 16 layer construction. Information that was provided on the nature of the failures (i.e., opens or shorts) included high resistance shorts that were occurring in those specified areas. The surface finish was a eutectic HASL (hot air solder leveling) and the solder paste used was a water soluble Sn/Pb(tin/lead)....
Advanced Packaging Technology
Oct 16, 2019 | ACI Technologies, Inc.
A major goal of the development of advanced packaging technology is to reduce the size, weight, and power consumption of electronics components using state-of-the-art commercial technologies. One of the novel concepts involves the use of all three spatial dimensions when designing and producing new systems. In the past, electronic structures tended to be two dimensional in nature. Generally speaking, individually packaged integrated circuit (IC) dies were interconnected on printed circuit boards. Techniques such as die and package stacking naturally contribute to a reduction of the spatial footprint of any given electronic system design. ...
Power Interfaces
Oct 07, 2019 | ACI Technologies, Inc.
Power interfaces are required when external power sources like solar panels, fuel cells, or batteries are used to generate power for electrical devices. There are two major power interfaces commonly used, direct current to direct current (DC/DC) converters and direct current to alternating current (DC/AC) inverters. While both interfaces are designed to convert from variable DC inputs, they output to different power standards and power levels that are used in different applications....
Cleanliness/Corrosion Mitigation
Sep 27, 2019 | ACI Technologies, Inc.
One of the most critical factors in preventing corrosion from occurring in electronics is maintaining the state of cleanliness. This is not an easy feat to achieve. Corrosion is defined as the deterioration of a material or its properties due to a reaction of that material with its chemical environment. [1] So, to prevent corrosion from occurring, either the material or the chemical environment must be adjusted. Adjusting the material usually means application of a protective coating or replacing a more reactive material with a less reactive material. Adjusting the chemical environment usually means removing ionic species through cleaning, and removing moisture, usually with a conformal coating or hermetic package. Ionic species and moisture are problematic because they form an electrolyte which is able to conduct ions and electricity. Any metal that comes into contact with the electrolyte can begin to corrode....
Non-Destructive Test Methods
Sep 23, 2019 | ACI Technologies, Inc.
Failure analysis (FA), by its very nature, is needed only when things goawry. Before any testing is performed on the sample, a decision mustbe made as to whether or not the sample is allowed to be destroyedin the process of testing. Non-destructive testing can allow for re-use of the assembly since the functionality is not altered, but there still remains the possibility that inadvertent damage can occur through the course of the analysis. If non-destructive testing is preferred, then the following types of analysis can be performed. The testing can be divided into four categories: visual, X-ray (X-ray imaging and X-ray fluorescence), cleanliness (resistivity of solvent extract, ion chromatography, and Fourier transform infrared spectroscopy), and mechanical (non-destructive wire bond pull)....
Virtual Manufacturing
Sep 16, 2019 | ACI Technologies, Inc.
“What is Virtual Manufacturing?” The simplest answer is a manufacturing simulation using a computer. The more complete answer is that virtual manufacturing is the process of designing a model of a real system and conducting experiments with this model for the purpose of understanding the behavior of the system. In today’s complex manufacturing environment, processes must be completely understood before implementation in order to “get it right the first time.” To achieve this goal, the use of a virtual environment is essential for simulating individual manufacturing processes and the total manufacturing system. By driving compatibility between the product design and the assembly plant process, these virtual tools enable the early optimization of cost, quality, and time to help achieve integrated products, process and resource design, and affordability....
Microscopy in Failure Analysis
Sep 03, 2019 | ACI Technologies, Inc.
Both optical and scanning electron microscopy (SEM) are powerful tools for failure analysis in electronics and are used for low and high magnification examination. This article will provide detailed, step by step information for examining solder joints....
Automated Testing with Boundary Scan
Aug 19, 2019 | ACI Technologies, Inc.
Boundary scan is a method for testing interconnects on printed circuit boards (PCBs) or sub-blocks inside an integrated circuit. It has rapidly become the technology of choice for building reliable high technology electronic products with a high degree of testability. Due to the low-cost and integrated circuit (IC) level access capabilities of boundary scan, its use has expanded beyond traditional board test applications into product design and service....
Selective Soldering and the Modular Approach
Aug 08, 2019 | ACI Technologies, Inc.
High mix production is the mainstay of many electronics assembly plants. Lot sizes and board complexities vary and the boards are often mixed technology, comprising a blend of both surface mount and through-hole technology. Modularizing a production line enables a clear distinction between one type of assembly process and another. This article assumes a modern factory where a job can be routed to the selective soldering machine module, the hand assembly bench, or a combination of both. The decision rules of routing a circuit board through hand assembly versus automated selective soldering are discussed. Hand assembly soldering operations require no explanation....
Attaching Fiber Optic Modules
Aug 01, 2019 | ACI Technologies, Inc.
Optical fibers transmit information in the form of pulses of light. The advantages of optical fibers over traditional copper wires include: higher throughput, greater signal distance and speed, smaller cable mass and diameter, greater pull tension limit, and resistance to electromagnetic interference (EMI) and radio frequency interference(RFI). The disadvantages of fiber optics when compared to copper wires include: end-face defects, cleanliness, and the ease of attaching connectors to electronics assemblies (Figure 1)....
Conformal Coating Processes
Jul 29, 2019 | ACI Technologies, Inc.
ACI Technologies can assist its users with process development and experimentation through the use of the conformal coating capabilities in the Demonstration Factory. Four types of coating processes are available at ACI Technologies: dip coating, manual spray coating, programmable spray coating, and manual brush application. (Manual brush application will not be discussed in this article.)...
A Systematic Approach to RoHS Analysis
Jul 19, 2019 | ACI Technologies, Inc.
One of the most frequently asked questions of ACI Technologies (ACI) is how to qualify and verify that the electronic systems shipped by their respective companies are Restriction of Hazardous Substances (RoHS) compliant. The RoHS directive has been implemented since July of 2006, and the preoccupation with what constitutes a compliant product continues to confuse the electronic industry. ACI receives countless inquiries regarding how to qualify and verify that the electronic systems shipped by the irrespective companies are RoHS compliant. The approach to proving compliancy requires a sequential analytical process that utilizes a decision flow chart....
Design of Experimentation for Affordability
Jul 11, 2019 | ACI Technologies, Inc.
Affordability is not exactly the primary word which comes to mind when discussing the use of design of experiments (DOE) principles, but is generally accepted as a necessary part of the engineering activities required in the development of a product or process. However, a number of studies have indicated that the cost savings derived from a well deliberated experimental design can be substantial in the initial stages where the conditions or parameters of a process are determined. Some studies have shown a greater than 50% cost savings compared to the more conventional means of trial and error approaches to process development. At ACI Technologies (ACI), we have found the use of DOE techniques fundamental in eliminating extraneous costs otherwise spent on unnecessary testing....
Fourier Transform Infrared Spectroscopy
Jul 05, 2019 | ACI Technologies, Inc.
Fourier Transform Infrared (FTIR) spectroscopy exists as one of the most powerful techniques for chemical identification and the most practical for “first step” analysis. Analytical instrumentation such as GC-MS and LC-MS are commonly used for identifying organic compounds. However, these techniques are costly and often require extensive set up time, method development, and sample alteration. Reliance upon FTIR as a robust and versatile tool can be based on its attributes of simplicity, speed, sensitivity, and affordability....
Computer Aided Design, Manufacturing, and Engineering
Jul 01, 2019 | ACI Technologies, Inc.
In the electronics industry of today, companies emphasize better quality, lower cost, and shorter lead time on their products in order to keep up with their competitors. ACI Technologies (ACI) has been utilizing Computer Aided Design (CAD), Computer Aided Manufacturing(CAM), and Computer Aided Engineering (CAE) in its development of advanced electronics systems. CAD utilizes computer systems to assist in the creation, modification, analysis, and optimization of a design [1]....
Manufacturing Cost Reduction through Automation
Jun 24, 2019 | ACI Technologies, Inc.
Defense systems and its manufacturers are often blamed for not embracing new and innovative technologies to manufacture products compared to its commercial counterparts. Commercial product manufacturers are known to think “outside the box” in coming up with new products which are cheaper, have fewer parts, and easier to manufacture using automation. Automation leads to consistent quality products which are reliable and reproducible. Implementing some of these producibility design practices into defense systems will greatly reduce the cost and insertion time for new products....
Investigation of Through-Hole Capacitor Parts Failures Following Vibration and Stress Testing
Jun 21, 2019 | ACI Technologies, Inc.
Recently, an ACI Technologies (ACI) customer called to discuss failures that they had observed with some through-hole capacitor parts. The components were experiencing failures following vibration and accelerated stress testing. Upon receipt of the samples, ACI performed three levels of inspection and Energy Dispersive Spectroscopy (EDS) testing to investigate the root cause of the failures. These analyses enabled ACI to verify the elements comprising the solder joints and make the following recommendations in order to prevent future occurrences. The first inspection was to investigate the capacitor leads using optical microscopy, and no anomalies were found that could indicate bad parts from the vendor or improper handling prior to assembly. However, vertical fill in the barrel of the plated through-holes was too close to the IPC-A-610 minimum specification of 75% to determine a pass/fail condition, and therefore required further investigation....
Tin Whiskers: Mitigation with Conformal Coatings | Part II
Jun 20, 2019 | ACI Technologies, Inc.
One of the two basic risks of employing the commercially accepted, Restriction of Hazardous Substances (RoHS) compliant, lead-free (Pb-free) electronics is the threat to the electronics reliability from the growth of tin whiskers. The other basic risk deals with Pb-free solder joint reliability....
Tin Whiskers: Risks with Lead Free | Part I
Jun 19, 2019 | ACI Technologies, Inc.
Tin (Sn) metal displays the characteristic of growing “tin whiskers” from pure tin coatings (most actively on relatively thin, electrodeposited or immersion tin coatings), usually months or years from the initial deposition of the tin. Tin whiskers are electrically conductive, filamentary, single crystals of white (beta phase) tin. These filaments of single crystal tin are usually one to five microns in diameter, and a few microns up to several tens of millimeters long, that grow spontaneously from the tin coatings. Alloying additions of several percent (by weight) of lead (Pb) prevents these electrically conductive tin whiskers from growing. Pb alloyed into the Sn was discovered to prevent the occurrence of tin whiskers in electronic assemblies in the 1950s as the Bell Laboratories solution to the problem of tin whiskers. The alloying of the tin with lead has thus quietly averted incalculable losses from short circuits in electronic equipment for the last 60 years....
Use of Pelseal® 2078 Viton® Caulk in Decapsulation of Electronics Components
Jun 18, 2019 | ACI Technologies, Inc.
ACI Technologies is tasked with decapsulation of electronics components for testing and investigative purposes. In the normal method of decapsulation, an analyst will drill a small indentation, with a rotary tool, in the hermetic sealant material and then apply Nitric acid to eat through the polymeric encapsulant....
Fiducial Marks
Jun 17, 2019 | ACI Technologies, Inc.
Very often pick and place machines are programmed using CAD data. This data increases the accuracy, precision, and repeatability of its component placement objectives. CAD data makes fine pitch and small component assemblies repeatable, but cannot adjust to a particular board unless it is exactly the same size and shape of the original board used for programming. The process by which printed circuit boards (PCBs) are made only allows some minor changes inboard size and shape, but these small differences are enough for parts to be misplaced. For this reason we use fiducial marks to increase the chances of precise component alignment....
BGA Placement on Rework Station
Jun 12, 2019 | ACI Technologies, Inc.
The success of ball grid array (BGA) placement on electronic assemblies is as much a matter of proper preparation and planning, as it is technique. In some designs, it is more appropriate to apply BGAs using a rework station that isolates the placement of the device, without subjecting the entire assembly to thermal reflow. This is especially beneficial in board constructions where the number of BGAs is limited, and the application of the solder paste is difficult, due to small pitch features that stretch the limitation of the stencil construction. Another application for rework stations, involves very large and thermally conductive BGAs, which will not uniformly reflow with other components on the assembly, and may require special process parameters for their proper placement. The most common use of BGA rework stations are for assemblies requiring BGA removal and replacements due to failures in the initial assembly stage....
Reflow Experiment
Jun 11, 2019 | ACI Technologies, Inc.
An experiment was recently performed ACI Technologies for a customer that was interested in comparing the wetting of lead-free solders with varying temperature profiles and atmospheric conditions. In order to deliver an objective measurement of solder wetting (in addition to subjective inspection analysis), a simple wetting indicator pattern was added to the solder stencil in an area on the test vehicle that had exposed and unused copper....
Component Failure Analysis - Hermetic Packaging
Jun 11, 2019 | ACI Technologies, Inc.
Recently ACI Technologies was asked to perform failure analysis on a hermetically sealed transistor for potential electrostatic discharge (ESD) or electrostatic overstress (EOS). ACI was asked to determine if the field-failed transistor was damaged by ESD or EOS. In order to properly assess the failure, additional samples were requested....
Surface Finish Issues Affecting Solderability and Reliability
Jun 07, 2019 | ACI Technologies, Inc.
ACI Technologies was contacted in regards to poor solder joint reliability. The customer submitted an assembly that was exhibiting intermittent opens at multiple locations on a ball grid array (BGA) component. The assembly’s functionality did not survive international shipping, essentially shock and vibration failures, immediately making the quality of the solder joints suspect. The customer was asked about the contract manufacturer and the reflow oven profile as well as the solder paste and surface finish used. The ACI engineering staff evaluated the contract manufacturer’s technique and determined that they were competent in the methods they used for placing thermocouples in the proper locations and developing the reflow oven profile. The surface finish was unusual, but not unheard of, in that it was hard gold over hard nickel, rather than electroless nickel immersion gold (ENIG). The customer was able to supply boundary scan testing data which showed a diagonal row of troublesome BGA pins....
Advanced Packaging of SMT Assemblies for Greater Cost Reduction
Jun 06, 2019 | ACI Technologies, Inc.
Legacy electronics assemblies, such as through-hole (Figure 1) and connectorized component packages, are robust and prevalent throughout industry. However, each of these assembly methods have reached their limits in terms of weight, volume, reliability, and most importantly cost. With cost reduction of assemblies now the primary focus area throughout the electronics industry, there is more of a need than ever to implement the latest advancements in surface mount technology (SMT) into electronics assembly designs. Although SMT has been utilized in the electronics industry for many years, implementation of the technology is still in the ever-evolving process of reducing component footprint size, component spacing, and component I/O pitch. Implementation of the most up-to-date SMT processes provides optimal weight, volume, and cost savings, for any type of assembly....
Ceramic to Plastic Packaging
Jun 05, 2019 | ACI Technologies, Inc.
As electronic products increase in functionality and complexity, there is an emphasis on affordability, miniaturization, and energy efficiency. The telecommunications, automotive, and commercial electronic markets are the leading drivers for these trends. These markets see high volume manufacturing with millions of units priced to the fraction of the cent. The choice of the packaging material for the electrical components for these markets can have a substantial effect on the cost of the final product. Therefore plastic encapsulated components are almost universally used in non-military applications over the conventional ceramic or metal electronic packages....
Platings for Interconnections
Jun 04, 2019 | ACI Technologies, Inc.
Interconnection technology relies very heavily on the ability of the conductors on a printed wiring assembly to maintain reliable signal integrity. Harsh environmental factors can precipitate a loss of conductivity due to oxidation and corrosion. Connections are typically soldered or inserted using pressure fitted connectors to obtain enough surface contact to meet the electrical conductivity requirements. In pressure contacts, surface integrity is especially critical where the abrasive effects of retraction and insertion can wear off the metallic finish from the contact area. This can expose the underlying copper or nickel and lead to increased resistance at the contact points. These types of conductors are frequently found in card edge connectors where the terminations are plated with a layer of nickel and gold (frequently referred to as gold fingers). A hard gold is typically used containing very small amounts of nickel and cobalt to increase the wear resistance....
Corrosion Analysis
Jun 03, 2019 | ACI Technologies, Inc.
ACI Technologies was pleased to assist a customer by conducting elemental analysis on several assemblies displaying severe corrosion. Several board assemblies had failed in the field and exhibited areas of corrosion in close proximity to onboard components. The most common source of corrosion on electronic assemblies is residual flux. Fluxes are specific chemistries applied during the soldering process which improve the wetting of the solder to both the pad and component when forming the solder joint. They can be highly reactive chemicals that, if left on the assemblies, can lead to corrosion, electrical degradation, and decreased reliability. In the presence of moisture and electrical bias, flux residue can enable dendritic growth as a result of electrochemical migration (ECM)....
The Power Packaging Laboratory at ACI Technologies
May 31, 2019 | ACI Technologies, Inc.
Microelectronics is the manufacture of systems built from extremely small electronic components. In today’s electronic world, devices must be portable, equipped with wireless technology and are driven by size, weight, power, and cost (SWaP-C). These system level drivers are crucial to all current and future electronic applications from personal computers and cellular telephones to military-fielded hardware, biomedical instrumentation, and space-flight hardware....
SMT Component Reliability for RF Applications
May 31, 2019 | ACI Technologies, Inc.
ACI Technologies (ACI) characterized the reliability of surface mount RF components. The RF frequency band of interest was the X band (10.7 to 11.7GHz). A two pronged test for reliability of circuit card assemblies (CCA) was designed for both extreme thermal cycling and vibration. The rapid thermal cycling and extreme vibration testing simulates the total stress encountered by the assembly over the life of the product but accomplishes it in a relatively short period of time. In order to perform the reliability testing, a test vehicle consisting of a printed circuit board with test structures and components, was designed, fabricated, and assembled at ACI....
COTS Cooling
May 31, 2019 | ACI Technologies, Inc.
ACI Technologies (ACI) is working on a project where one of the challenges is removing a large quantity of heat from audio amplifier circuits. This challenge is further complicated in that the heat generating circuits are located in a rack mounted box that needs to be shielded from electro-magnetic interference (EMI). Mechanically, this means that there cannot be open passages into the rack mounted box. We will first review the basic types of cooling available as commercial off-the-shelf (COTS) systems for the electronics industry, then discuss the pros and cons of each for different applications, and finally reveal the criteria and solution for the ACI project....
Thermal Interface Materials Testing
May 30, 2019 | ACI Technologies, Inc.
There exists a need to efficiently remove heat from power electronics within power systems to enhance performance. Thermal management is a critical function to that operation. Reducing the junction temperature of semiconductor power electronic devices enables them to operate at higher currents. Lowering operating temperatures reduces the thermal stress on electronic devices, which improves efficiency and reduces failures. To improve the heat removal process, the current heat transfer design of a power system has been analyzed and a variety of thermal interface materials (TIMs) and cold plate technologies have been evaluated. This paper will review some of these results....
Identifying Battery Load Qualification Test Parameters
May 30, 2019 | ACI Technologies, Inc.
In a previous Tech Tip (see Battery Selection for Electronic Systems), considerations were discussed for selecting an appropriate battery for an application. After selection, testing should be performed to confirm that the battery can provide the power required for the specific application. Some battery definitions should be understood when discussing power load qualification testing of batteries....
BGA Reballing
May 30, 2019 | ACI Technologies, Inc.
In the current economic environment, the ability to reuse ball grid array(BGA) components that have failed due to solder defects may be an efficient way for electronics manufacturers to reduce costs. Cost may not be the only driving factor in the decision to engage in this recycling practice. The increasing demands placed upon the complexity of microprocessors and integrated circuits (ICs) has decreased the availability of some components, and increased their lead time. Because of this, reballing may provide a means to meet schedule, reduce rework turn-around time, and give a manufacturer a decisive advantage over other companies in an ever increasingly competitive market. This article will discuss the process of reballing BGA components (Figure 1), examining preparation (the preform method, the screen method), and cleaning and bake-out....
Battery Selection for Electronic Systems
May 29, 2019 | ACI Technologies, Inc.
Battery selection should be considered early during the design phase of affordable electronic systems. The important choice of an appropriate battery can reduce system acquisition costs and keep logistics support costs down for the life of the system....
Design for Test
May 29, 2019 | ACI Technologies, Inc.
Design for Test or Design for Testability (DFT) can best be described as the techniques utilized to add testability features to an electronic hardware product design. These added features make it easier to develop and apply manufacturing tests to assure that the product functions correctly....
Decapsulation of Integrated Circuits
May 29, 2019 | ACI Technologies, Inc.
Decapsulation, or de-cap, is a failure analysis technique which involves the removal of material packaging from an integrated circuit (IC). After de-cap, visual inspection by optical microscopy of the internal circuitry may reveal areas where damage is most likely to have occurred. In addition, scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS) can identify the composition of any anomalies present after de-cap under higher magnification. The removal process of package material can be done either mechanically or chemically depending on the design of the integrated circuit. With ceramic packaging, de-cap is usually done mechanically by chiseling off the top with a fine razor and small hammer. For plastic packaging, de-cap requires chemical etching by strong acids. In this Tech Tips article, de-cap by chemical etching will be outlined step by step....
Decapsulation of Integrated Circuits
May 24, 2019 | ACI Technologies, Inc.
Decapsulation, or de-cap, is a failure analysis technique which involves the removal of material packaging from an integrated circuit (IC). After de-cap, visual inspection by optical microscopy of the internal circuitry may reveal areas where damage is most likely to have occurred. In addition, scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS) can identify the composition of any anomalies present after de-cap under higher magnification. The removal process of package material can be done either mechanically or chemically depending on the design of the integrated circuit. With ceramic packaging, de-cap is usually done mechanically by chiseling off the top with a fine razor and small hammer. For plastic packaging, de-cap requires chemical etching by strong acids. In this Tech Tips article, de-cap by chemical etching will be outlined step by step....
Coating Application Methods
May 24, 2019 | ACI Technologies, Inc.
Conformal coatings are applied to Printed Circuit Board Assemblies(PCBAs) using a variety of different methods. There are six main methods of applying conformal coatings: manual spraying, automated spraying, dipping, brushing, selective coating, and vacuum deposition....
Preparation for Reflow Profiling
May 24, 2019 | ACI Technologies, Inc.
There is a smaller process window and a much narrower margin of error when creating and using lead-free reflow profiles for surface mount parts on printed circuit boards (PCBs). Solder balls, dewetting, tombstones, voids, and head-on-pillow problems will occur much more frequently because lead-free alloys behave differently than eutectic pastes. Problems are compounded due to the extra heat necessary for some lead-free pastes to reach their melting points....
Identifying Flux Residues
May 23, 2019 | ACI Technologies, Inc.
Why identify flux residues? The primary purpose of flux is to reduce species of metal oxides from solderable surfaces, and to act as a mechanism for lifting and removing debris. If the assembly is not properly cleaned after manufacturing, flux may continue to reduce metals and may eventually corrode the assembly. When the assembly is powered, the metal ions may precipitate along electromagnetic field lines and form dendritic shorts. In addition, the presence of residue can alter the insulation properties of a board, affect the adhesion of the conformal coating, or interfere with the moving parts of the assembly. In radio frequency (RF) applications, flux may change the RF properties on the surface of the printed circuit board (PCB) such as the dielectric strength, surface resistance, and Q-resonance....
Cleaning
May 23, 2019 | ACI Technologies, Inc.
Solvent and co-solvent cleaning involves the use of engineered solvents in a vapor phase system. The solvents classically used were Class 1 Ozone Depleting Substances, but new types of solvents have been developed that are less environmentally harmful. In some cases, isopropyl alcohol is used with a co-solvent. In these types of cleaning systems, a cloud of boiling vapor solvent is maintained between a boil sump and a cooling coil. When the items to be cleaned are immersed in the vapor cloud, the solvent condenses on the assemblies and acts to dissolve the residues. These processes usually involve a final rinse step outside of the vapor cloud to ensure that all dissolved residues are washed off the assemblies (Figure 1)....
Wedge Bonding Tool Selection
May 23, 2019 | ACI Technologies, Inc.
Increasing I/O numbers, device complexity, and product miniaturization requires high precision bonding tools, and sophisticated equipment. Careful consideration should be given to wedge geometry while selecting the tool for a fine pitch wire bonding application. Wire bonding is a process that creates an electrical connection between a die and a substrate or lead typically using gold or aluminum wire. Wedge bonding is a specific type of wire bonding that uses a wedge shaped tool to create the welds. The design of the wedge tool has changed very little over the past decade. The wire is fed at an angle through the back of the wedge. This angle is typically 30 to 60 degrees and is application dependent. Some applications require a higher feed angle due to package clearance issues. Some deep access applications require a 90 degree feed angle. In this configuration, the wire is fed through a hole in the shank of the wedge tool. Wire feed is shown in Figure 1....
Experimentation for Success
May 23, 2019 | ACI Technologies, Inc.
The technical tips have offered valuable details and techniques into various aspects of electronics manufacturing. This has been validated by the reader responses concurring with our assessments, offering additional insight, or in some rare cases, stating divergent points of view on any particular matter. In a bit of a strategic departure from the normal range of electronic manufacturing topics, ACI Technologies,Inc. would like our readers to consider the importance of being well prepared in the arena of designed experiments in order to properly qualify a manufacturing process. This particular topic has relevance because of the associated scope of work ACI Technologies encounters in numerous projects from material R&D to manufacturing process optimization, which require appropriate experimental designs to ascertain the significant data....
Flip Chip Attach Techniques
May 21, 2019 | ACI Technologies, Inc.
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)....
Flip Chip Rework
May 21, 2019 | ACI Technologies, Inc.
Flip chip components have been gaining popularity in the electronics industry since their introduction in the 1960s. Advances in attach methods and adhesives, as well as the drive for smaller and faster electronic devices made the technology take off. The basic premise of the flip chip is that the chip (semiconductor device) is mounted flipped from the traditional position. The traditional method of mounting a die is to mount it on a lead frame with the circuit and bond pads face up. The bond pads then receive a bond wire which then connects to the proper lead on the lead frame. Flip chips are mounted face down onto a substrate using small bumps on the bond pads to make direct electrical connection to their respective pads on the substrate. Stay tuned for more information on attachment techniques next month. This article will focus on how to rework flip chips....
Conformal Coating Inspection
May 21, 2019 | ACI Technologies, Inc.
In the field of electronics manufacturing, the end use of the product will always dictate the processes, procedures, and methods, not only for building the product, but also for testing, cleaning, and protecting the assembly in order to assure the level of quality required for proper operation. The need to protect an electronic assembly from its end use environment may stem from anyone of a number of hazardous (or potentially hazardous) conditions. Choosing the type of protective material is dependent upon matching that material’s characteristics with the conditions to be overcome. Naturally, the use of a protective (conformal) coating will require some method of verification to ensure the desired level and type of protection is achieved....
Thermal Profiling for Reflow
May 21, 2019 | ACI Technologies, Inc.
Reflow temperature profiling is the most important aspect of proper control of the solder reflow process. It may appear to some to be a magical art practiced by a select experienced few, who are able to divine the proper settings for a reflow oven by reading graphs as if they were tea leaves. This does not have to be true. This article outlines a systematic method by which engineers and technicians can implement a successful reflow process from scratch....
Die Attach Dispensing Methods
May 21, 2019 | ACI Technologies, Inc.
Die attach material selection and process implementation play crucial roles in any microelectronic assembly. The chosen attach methods ultimately affect die stress, functionality, thermal management, and reliability of the assembly. Die attach applications are designed to optimize mechanical attachment of the die to the substrate, to create a thermal path from the die to the substrate, and to create an electrical path for a ground plane connection. Some of the more commonly used die attach materials in the microelectronics industry today are epoxies,polyimides, thermoplastics, silicones, solders, and special low outgassing, low stress, anisotropic adhesives. ...
