For BGAs it is best to start with a top-down view to look for obvious shorts and over-large voids, and then go to oblique views.
X-ray inspection, at present, requires mainly human analysis to see the flaws. This will be true perhaps unless, or until, artificial intelligence (AI) algorithms provide some alternative solution. However, with so many variables in the x-ray images of assembled boards – the shapes, sizes and density of bumps and joints, the differences in pad solder coverage, the presence of internal copper traces, the overlapping internal and bottom-side components and features, etc. – obtaining an initial training set of exemplars for a ubiquitous AI solution may be tricky.
I suggest this is particularly the case when looking for opens in BGAs. By looking only at a top-down x-ray view, you may miss the fault. In previous columns, I have recommended oblique x-ray views should also be taken to separate the pad and device interfaces from each other and thus give the (human) operator the best chance to spot the open joint or other problem(s). Consider using not only an oblique angle view, but also decide what angle, or angles, are necessary and in which direction(s) around the joint those angle views should be taken.
The balancing of “intelligence” and “smart” is an age-old conundrum.
The rage these days is something called “Industry 4.0.” I have been invited to scores of presentations designed to show how Industry 4.0 is not just the next generation of manufacturing, but a must-do next step to produce higher quality product, faster, on-time, and at far less cost. Industry 4.0 sounds exciting and novel, so I have participated in webinars, attended seminars and read up on this must-do phenomenon.
Spoiler alert: It’s not all that new!
Last month, a California jury awarded a resident $289 million, finding he had developed cancer from exposure to a popular brand of herbicide.
What, you may ask, does a guy who used Roundup to kill weeds around school buildings in the San Francisco Bay area have to do with me in the printed circuit board industry?
A lot, potentially.
I had the pleasure in August of interviewing Brenda Baney for our PCB Chat podcast. As some readers may remember, Baney previously was a regular in these pages. She was an excellent columnist: knowledgeable, opinionated and articulate. After two decades at Delco, she now runs B Cubed Consulting, where she provides expert guidance on conflict minerals, RoHS and REACH product stewardship, and the International Material Data System.
There are times increasing inventories and AVLs makes sense.
A constrained supply chain represents a challenge to Lean manufacturing processes, but in the electronics manufacturing services (EMS) market, the bigger challenge is often OEM misperceptions about strategies to address this. From a Lean perspective, navigating a constrained supply chain often requires taking one step back to move two steps forward.
Our November 2017 column discussed several areas where the best strategy was “at odds” with Lean manufacturing principles, including:
Microvias have a domino effect, increasing available copper and lowering resistance.
Today electronic devices typically use designs with complex requirements that only high-density interconnect (HDI) technology can meet. Component manufacturers support the move by making components with smaller pitches. Because they are using more I/O connections, larger FPGAs and ASICs operate at higher frequencies, and the sharper rise times require smaller PCB features. The HDI PCB process supports these requirements exceptionally.
HDI PCB designs use microvias that offer a number of electrical benefits, and they also improve the power integrity of the assembly. This enhanced integrity comes from such sources and enhancements as decoupling capacitors, presenting a smaller mounted inductance, and chip pinouts requiring fewer perforations, thus delivering better performance from planes. The HDI PCB process also uses dielectrics of different thicknesses that reduce plane capacitance compared to conventional design.
Too much heat during reflow can force solder out of a BTC.
FIGURE 1 shows examples of solder beads after reflowing bottom termination components (BTC). The beads are related to placement force prior to reflow, where the solder paste deposit is displaced away from the pads before reflow soldering. It is uncommon, but solder beads have also been seen coming from the package itself due to excessive heat during reflow. Solder beads or balls on the side of packages and close to the board surface are related to paste printing, paste volume, stencil design, PCB pad size, placement force or reflow, and can easily be demonstrated.