International Edition

  • The art or science of BGA inspection and the pitfalls of cost to performance 

    BGA Picture1

    By Joe Booth, CEO, Altus Limited

    Ball Grid Arrays (BGAs) are one of the most talked about components in the electronics industry today. Whether it is shortages in the supply chain, increased traceability requirements, or yield issues of these high value parts, you are not alone in experiencing problems. Fear not as there are a number of checks and innovative strategies that can be adopted to mitigate risk. 

    These next paragraphs will lay out the differing options for a variety of budgets that can be introduced depending on your appetite for upskilling, or your desire to deskill and automate the tricky element of quality assurance on the production line. 

    Are you Maximising the Tests from AOI?

    The first option is in part reserved for SMT manufacturers that have purchased fully 3D metrology based AOIs. Light measurement platforms are the first option to look as they are an easy to implement quality check post reflow using BGA coplanarity analysis and positioning. This is a superficial check as the internal solder balls are not inspected. However, overall height and levelness of the BGA offers the first insight into the reflow performance and if the BGA was successfully soldered when compared to test measurements set with suitable tolerances. If a BGA fails to meet the test thresholds set for good performance, operators recognise that they should pay special attention to the downstream inspection ahead. Furthermore, historic production data can be used to tighten tolerances. This becomes more and more accurate over time using predictive data. 2D, top down or non-measuring AOIs cannot offer this insight. 

    Optical BGA Inspection Devices 

    There are a few BGA inspection systems on the market including those from Swedish company Optilia, the originator in the BGA inspection field. BGA inspection devices offer an excellent entry point for a facility looking to increase their capacity to inspect and review BGAs but with a limited budget. 

    The inspection device in its simplest form is a handheld optical microscope. It can use a variety of lenses, depending on pitch and the magnification required, to provide an image of the internal rows of solder balls. 

    Moving up the commercial scale, the next option is to add fixed mounts, extra lighting, additional lenses, movable X-Y tables and Optipix software. These additions give manufacturers the ability to reduce the skill level required to achieve a good image of the solder balls. 

    BGA inspection systems require some skill and learning of what parameters provide the very best image. However, with suitable lighting and magnification the system provides top quality subjective assessments of BGA soldering performance for up to 20 rows of solder balls. When Optipix software is added, you bring in more quantifiable capabilities to capture and measure the shape and size of balls. This process would be more suited to low volumes or batch inspection. Systems can range from 5K Euros to 15K Euros depending on configuration. 

    X-ray Inspection Providing Options for Automation 

    Sites can be put off by X-ray platforms because they are anchored by the traditional incumbents system costs that use open source technology and expensive hardware. Many companies are unaware that a suitable X-ray for single sided PCB inspection costs as little as $70K (65k euros) with a fully loaded system coming in at under $120K (110k euros). Clearly there is a jump up in price from optical devices but with the increased investment comes a significant reduction in skill level and an uplift in automation and throughput potential. 

    Simple single sided PCBA inspection can be reliably completed with 90kV of power. However,  depending on the board design, for example, if it is double or single sided, or if the application has cans or shields, the requirement for more X-ray power could increase to 110kV or even 130kV. 

    With double sided products and BGAs which are commonly the sandwich bread of the PCB, an oblique angle tilt and rotation could be a welcome addition to enhance inspection abilities. Once a suitable machine has been selected the rest is pure automatic bliss. 

    Most X-ray systems these days come with automatic void calculation software and algorithms removing the skill required once the program has been created. The system will pass or fail products based on IPC 3, 2 or 1 criteria of void percentage and the largest void. It will also create automatic reports which can be stored against product barcodes for effective traceability. For NPI and process development, the same automatic software can be used as engineers assess first offs and process tweaks to quantifiably assess if a correction is in the right direction to improve the yield. 

    The latest X-ray systems can be batch which may be very affective for a lower volume producing manufacturer or inline. Clearly with batch systems there is a significant ROI when it comes to boosting throughput, increasing traceability and reducing risk around the requirement for a skilled inspector in comparison to other more rudimentary process equivalents. In many instances these pain points or a prior escape to a customer are enough to justify an investment. One consideration is that with any batch system, there is the cost of an operator to factor in who will need to be present when the machine is in use. 

    Those looking for more automation could consider an inline X-ray system at increased cost but with higher long term product profitability. Inline systems have the same software capacity as the batch versions but with other significant throughput benefits that can be useful for those with large volume production or ambitions to get closer to a lights out factory of the future. Certainly, the initial investment can be considered larger due to the increased hardware required to conveyorize the system. Additionally, there is also the required handling both upstream and downstream to support an automated X-ray island that separates NG/GD with enough capacity to be hands off. However, there is a significant saving in operator involvement. The cost of a hands-on worker is removed for the time the unit is running except to periodically take off the full magazine racks and consistency of inspection is dramatically reduced. 

    Summary

    As already highlighted, there are several options to consider when upgrading your current BGA inspection processes, checks and balances. Some provide predictive results, others offer subject results with more skills needed to qualify. The gold standard option automates the whole task and intuitively provides outputs. Knowing the best option for a specific BGA production line can be a minefield. At Altus we can act as a sound board and support samples validation, demos and trials to establish which solution would best fit a company’s needs and budget. 

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