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.

With the growth of Surface Mount Technology (SMT) driven by new technological innovations and next generation products, machine feeder density becomes extremely important in electronics manufacturing. 

As products become more intelligent, diverse and efficient, the associated product BOM (Bill of Materials) and parts diversity increases in scope. This increase in parts count and diversity per product drives the necessity for higher feeder density per Pick-and-Place (P&P) machine.

This per machine feeder density also becomes critical when constructing and accurately determining the potential SMT production lines to fulfill customer needs without resulting in an excess or ‘over capacity’ situation. Constructing a SMT production line based on the requirement of feeder input vs. CPH (components per hour) increases the capital equipment cost of the P&P segment of the line. With a larger percentage of the P&P equipment cost associated to CPH rather than the amount of feeder inputs available at the machine level, in essence end users pay more for CPH vs. feeder inputs. With current and future consumer demands for ever increasing product intelligence this creates an under achieving or underutilized capacity production line for manufacturers.

A balance between machine feeder inputs needed for product diversity and CPH to meet customer required volumes is essential for the highest efficiency production lines.  One way to increase the feeder machine density is to utilize the thinnest feeder possible or to combine feeder positions, forexample, 2 for 1 or 2 for 3. A disadvantage of a combined feeder input solution is reduced ease of use and flexibility. Utilizing a single input feeder increases ease of use and adds the highest level of flexibility to accommodate the most diverse products now and in the future.

Feeder per machine density can be measured in 2 ways, either by total amount of 8mm inputs per linear meter or total amount of 8mm inputs per m². Of course a higher number results in higher production flexibility to address product diversity without creating an over capacity production line.

In order to keep up with the fast moving consumer products technology and diversity, P&P machine suppliers must increase feeder density in traditional ways or by means of new creative innovations to better serve the end user.

Customer demands for smaller form factor electronic devices are driving the use of thinner electronic components and thinner printed circuit boards (PCB) in the assembly process. The use of thinner components and thinner multi-up panel PCBs (≤ 1 mm) has led to PCB warpage issues in the surface mount (SMT) assembly process, which in turn impacts the PCB assembly yield. PCBs with excessive warpage impact paste print quality in the print process, and solder joint formation during reflow soldering leading to SMT assembly defects. Lack of industry standard for PCB warpage at reflow temperature further compounds the PCB warpage risk to SMT assembly yield. This paper will use high temperature warpage metrology to evaluate the impact that PCB manufacturing, design, and material has on ball grid arrays (BGA) and panel area PCB warpage by varying the PCB post processing (Bake vs. No-Bake), panel location (corner vs. center), PCB thickness (0.8 mm vs. 0.6 mm), Material (Mid Tg vs. High Tg), and processing (i.e. lamination at condition A vs. B).

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