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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Intended for use as technical guidance by ADHP (Aerospace, Defense, and High-Performance) electronics system customers to provide the technical structure needed to allow the designer to evaluate the options for using Pbfree BGAs in an assembly that has not converted to full Pb-free assembly

J-STD-001G Amendment 1 standard requires an OEM and EMS to qualify soldering and/or cleaning processes that result in acceptable levels of flux and other residues. Objective evidence shall be available for review. The use of the historical 1.56 μg/NaCl equivalence/cm2value for ROSE, with no other supporting objective evidence, is not considered acceptable for qualifying a manufacturing process.

The core concept for materials compatibility and residue acceptability is that of the qualified manufacturing process (QMP). In a QMP, manufacturing materials and processes used to qualify and validate production hardware confirm electrical performance in hot/humid conditions. The purpose of this research is to apply the methods documented in the standard to qualify and validate acceptable levels of flux and other residues when implementing a change in cleaning material and cleaning machine.

Findings and recommendations are reported from phase 1 of the Transient AMR(absolute maximum ratings) project, which is sponsored by the EOS/ESD Association and Industry Council on ESD Targets, and DfR Solutions. The project includes an industrywide survey about how AMRs of semiconductor products are determined and interpreted. Semiconductor manufacturers design the products to be reliable, as long as AMRs are never exceeded. Electronic system customers continue to increase their reliability expectations, especially in markets such as automotive. This project is of great importance to the electronics industry because customer returns of semiconductor parts continue to indicate that they have been overstressed, suffering electrically induced physical damage (EIPD). Transient excursions above AMR account for many failed parts, but root causes are difficult to discover as they happen unexpectedly, rendering the units unreliable. Manufacturers must ensure that published AMRs are clear and complete. Semiconductor customers and board and system designers must be educated to properly interpret AMRs on datasheets so they can take appropriate action to preserve the built-in reliability of semiconductor parts.

Project work is carried out at DfR Solutions, with some assistance by Industry Council representatives. Survey and literature search results will be summarized, including current practices regarding the determination, reporting, and interpretation of datasheet AMRs. Recommended best practices will be discussed. Case study examples from various companies will be shared anonymously.