The electronics industry is still searching for alternative lead-free alloys. Selective soldering requires relatively high solder temperatures to get proper hole filling. Alternative alloys with lower melting temperatures may wet faster and open the process window. These low temperature solders (LTS) are of interest in SMT soldering because of reduced warpage and voiding risks. The question is how these alloys respond in liquid soldering applications. Lower operating temperatures reduce the risk of damaging plastic parts or secondary reflow on mixed technology boards. The preheat temperatures are close to the melting point of the alloy which will make the solder flow easily to the solder destination side of the board. Fluidity of these alloys may change at higher temperatures and it will be interesting to see the impact of the melting range on solidification of the solder.

Other alloys are designed to be compatible with extreme thermal exposure in operating environments such as under-hood automotive, avionics/aerospace and other severe operating environments. Their wetting properties are important to get hole fill at reasonable solder temperatures. This study investigates new alloys and their properties in lead-free selective soldering applications. Does their fluidity influence the wave stability on wettable and non-wettable nozzles? The impact of the solder temperature on hole fill and bridging is tested. A test-board with fine pitch components from 1.00 mm to2.54 mm pitch is used to define the bridging risk.

There are new technologies on the market that make it possible to design very odd-shaped nozzles. De-bridging can be much more efficient with this second generation of non-wettable nozzles in combination with advanced nitrogen-gas nozzles to eliminate bridges. This patented nozzle technology will be compared to the conventional nozzles.

This paper presents results from a joined R&D project between two companies; Automotive Tier-1 and Technology Provider of structural electronics. Key benefits of structural electronics are 3-dimensional shapes, reduced thickness and weight as well as simplified assembly. The purpose of this project has been to evaluate structural electronics for automotive interior use. The car interior application is back-seat-control-panel and the structural electronics solution reduces thickness by 70 % and weight by 50 %. The back-seat-control-panel has been subjected to severe testing based on automotive OEM requirements. Environmental loads have been changing of temperature, combination of high humidity and changing of temperature as well as combination of UV-light and high temperature. None of the components failed during reliability testing.

Electronic components are exposed to impact loadings and mechanical vibrations during assembly, material handling, and transportation. These loadings might affect the fatigue life of solder joints and with decreasing size of packages and solder ball dimensions, it becomes more important to evaluate the reliability of these solder joints. In automotive and harsh industry applications, BGA packages are being widely explored and the reliability of this device-type has been the critical dampening factor in employing them. As a result, there has been an influx of newly doped lead-free solder materials in the market commonly referred as “high reliability alloys”, intended to last long in harsh environments.

A thorough investigation of the influence of solder paste alloy on the fatigue life of solder joints between ball grid arrays and PCB undergoing vibration fatigue test is performed. The test matrix comprises of four different solder materials with traditional SAC305 being the control. Initially, modal analysis was performed on the test boards to identify the natural frequencies.

A sinusoidal vibration test was conducted on the test vehicles placed on electrodynamic shaker. The test boards are excited at their natural frequencies and constant amplitude of acceleration until failure of all BGA packages. A strain gauge was mounted on the board to measure and keep track of the maximum principal strain throughout the test. Weibull analysis is performed to compare the vibration fatigue life of various solder alloys, and failure analysis is performed to study the failure modes. All tests were conducted at room temperature. Keywords: Vibration testing, Modal analysis, Sine dwell, Lead-free alloys

Radio Detection and Ranging (radar) sensors require specialized materials and specific tolerances in order to optimize their function. However, although not new to many markets, such as the military and telecommunications, some of these materials and design sets are novel to the automotive industry. Their use is growing rapidly with the increase in autonomous driving and safety systems.  Nonetheless, the specific design and fabrication bring challenges to the automotive supply chain.

As the automotive industry takes steps toward fully autonomous vehicles, there is a respective progression of increased safety systems in vehicles.  The increase in quantity and function brings significant change to the electrical content and its level of sophistication.  Historically, automotive circuit board assemblies were not considered complicated as they did not require fine features or advanced components. Now these aspects are a necessity as many systems require high density interconnect (HDI) designs with advanced packaging to support the processing and function of the safety systems.  The processing speeds involved in making safety critical decisions effect design, fabrication, and reliability of the components delivered into the automotive supply chain.

Degrees of autonomy are described in levels from 0 to 5, with 5 being fully autonomous.  Today, most cars function on a level of 1-2 with rapid growth in level 3devices that provide the user conditional automation. This paper will discuss the current areas of growth that support level 3 autonomy, with a focus specifically on radar modules that bring perspectives of distance and speed to surrounding objects. The various systems used to support the automation of driving are housed under the phrase Advanced Driver Assistance Systems or ADAS.

Advanced safety systems require the car to react in response to external changes surrounding the vehicle. This takes the decision-making process away from the driver, and therefore, reliability is of greater importance than ever. This paper will investigate the chemical process changes needed to improve reliability, specific for radar module builds. It will discuss how radar designs challenge Printed Circuit Board (PCB)fabrication, what reliability requirements are needed, and review certain improvement options necessary to create a reliable system, including packaging considerations.

Commonly used integrated circuits have been increasingly moving from leaded packages that are reworkable with a soldering iron to leadless packages such as BGAs that require complex rework that cannot be visually inspected to confirm success. BGA packages have been decreasing in ball spacing (pitch) and increasing in I/O(ball count) making commonly accepted/documented time-dependent hot air local reflow profile development techniques no longer optimal. At the same time, the complex PCB interconnect structures (and resultant sensitivity to thermal cycles) needed to support these packages drive a need for tighter process control which is not attainable by using the classic time-dependent reflow profile. These factors combine to drive a need to improve the supporting processes around complex hot air rework.  This paper addresses that need by providing:

• Background on prevailing standard practice time-dependent hot air reflow profile development and practical usage

• Summary of efficiency challenges and risks to achieving strong process control using this standard practice

• Explanation of a live-feedback touchless temperature-dependent reflow profile development and usage, including efficiency improvements created during development processes

• Experimental evidence demonstrating improved process control from a temperature-dependent live-feedback profile methodology

• Reviewing real-life risks (using FMEA-based thinking) and showing the increased variability tolerance to these using a temperature-dependent profile relative to classic time-dependent profile

• Practical manufacturing efficiency improvements gained by this updated basis of profile tracking

The overall goal of this paper is to share our complex rework process improvements forour colleagues in the electronics manufacturing industry to review and consider how incorporating into their practice can provide benefit to them as well.

Multiple Electronics Markets are driving the growing need for components with higher performance in smaller form factors with higher pin count and greater reliability.

Ball Grid Array’s (BGA’s) and Chip Scale Packages (CSP’s) are two of the most widely used components for higher pin count applications, however the addition of underfill is required to provide the level of reliability that is needed when these components are subjected to high thermal and mechanical stresses.

One downside of underfilling BGA’s and CSP’s is that it makes the rework process extremely difficult or impossible based on the underfill composition that is used. Current underfilled rework practices include Neanderthal terms such as a wooden pick, small chisel, exactoknife, prying, twisting or shearing the component to separate it from the underfill bond and scraping the underfill off the site. These manual rework methods lack the Process Control that is inherent in the initial board assembly process making rework the weak link for these high reliability applications.

This paper describes an alternate process for reworking underfilled components that provides machine-based Process Control and eliminates the non-repeatable, manual processes that are currently in use.

Whilst many forward-thinking companies invest time, effort and cost into up front work to fix snags which would lead to issues with yield during production, this paper shows the efforts of a company who take things further.

With increasing pressure on cost reduction within our industry, companies are looking ever more closely at their manufacturing process. In order to remain globally competitive and even to succeed in their local market every dollar saved here helps the bottom line. However, in many areas there is a danger that lower price equals lower quality and therefore actually higher costs in the end.

The approach here involves spending a little more money than normal at the start of project but less than hundreds of dollars and the results show savings of many times more than this outlay. However, it is acknowledged that this does take a little more time to get the job onto the shop floor.

The key to this methodology is that it needs the time and effort of a skilled team and time on a production line before the job is started. But as the paper shows it really does improve yield, reduce cost, save the potential issues around repair and gives better reliability.

In essence the results of the printing process are analysed, after the components are placed, using x-ray and these results compared to the results after reflow soldering. The resultant pre reflow solder paste shapes are impossible to see with the naked eye or by lifting the components, as the paste would not release evenly. This allows the engineer to determine how differences in printed paste shape and volume react when components are placed on them and how ultimately this affects product quality.

Post reflow problems including mid chip solder balls were found to be common faults, as were issues under BGA’s including insufficient solder and shorts.

The product is run on a “real line” and the results evaluated. Improvements are then made to the stencil design and other key process parameters to ensure that when in production the board is producing acceptable yields.

If you don't measure, you don't know. These are appropriate words for the application of statistical methods for measuring machine and process capabilities in surface mount technology (SMT) manufacturing.

Only through diagnostic measurement and analysis of SMT equipment can quality performance improvement be realized. Measured mean values can be used to ‘soft’ calibrate machines to a higher level of accuracy than available through original equipment manufacturer (OEM) standard calibrations.

With the complexity of high-speed automation combined with high accuracy requirements for product miniaturization, it is necessary to dig deeper with statistically significant data collection methods to understand and solve the root cause of sub-component machine failures which impact product quality.

When machines are allowed to run in ‘maximum accuracy mode', they are more confident and capable to produce today's high reliability electronics with fewer defects. Defect contribution in each process step needs detailed analysis to reduce cost. When costs are minimized, the underlying inherent process efficiencies go way up which contributes to higher productivity and bottom line profitability. The improvement effects of process optimization have a number of intrinsic benefits that can easily maintain high manufacturing productivity.

This paper discusses individual process step validation methods with real examples of improvement that contribute to defect per million opportunities (DPMO) reduction. In stencil printing the characterization considers accuracy of the alignment system and dynamic measurement of squeegee force. During placement, accuracy and placement Z-force are looked at to calibrate head/angle offset associations and dynamically check individual spindle forces and energy dissipation. All while each process step is characterized, the underlying objective is to verify OEM specifications and prove that machines are capable for intended quality performance. This allows engineers to streamline efforts and focus on other areas of improvement.