Simple process steps for inspecting arrays. (But don’t expect them to always be the source of failures.)

After more than 15 years working with people who choose to use x-ray inspection as part of their fault-finding and quality-ensuring procedures, the most common refrain I hear is, “The board’s not working; it must be the BGA.” I do also hear this from those who do not have access to x-ray!

Arguably, as the BGA was the first commonly used component to be placed on boards with all its interconnections hidden from any possibility of post-reflow optical inspection, I suggest the BGA has been the primary driver for the increased uptake of x-ray inspection in recent years. After all, x-ray inspection is nondestructive and can see where optical systems cannot. Perhaps it is the entirely optically hidden nature of the BGA joints that has caused its infamy within electronics manufacturing. By not being able to see the joints that have been made, how can the BGA be ruled out as the cause of the failing circuit? Without some certitude in this, how can a contract manufacturer assuage its client’s belief that all non-working products have been caused by poor reflow under the BGA, rather than by some other mechanism? X-ray inspection goes a long way to help both parties resolve this, and, assuming it isn’t actually the BGA’s fault, the “first likely cause of problem” can be ruled out, and all parties can move on quickly and productively to consider other potential reasons for the issue.

For leadless parts, the magic is in the method.

Solder dip or float testing is often used in the industry as it is quick, simple and cheap. But, it can lead to incorrect solderability assessments.

As seen in FIGURE 1, the solderability of the terminations was good, but the test method for this type of a bottom termination component (BTC) is not appropriate.

Data distribution, explained.

In my December column I listed three items to watch out for when evaluating capability study results: Cp versus Pp, the distribution of data, and sample size. I hopefully cast some light on the differences between the two measures of capability, Cp and Pp.

In this column I will dive deep into the distribution of data. The thing to remember is the standard capability study assumes the data are normally distributed. This assumption of normality, while not so critical in other statistical tools, is very important in capability studies.

Cp and Pp give us predictions based on a sample of how our population will behave in the far tails of the normal curve. These measures use mean and standard deviation to create a normal distribution, and, from this, predict how many of our parts, over the entire population of parts, will fall outside the tolerance limits.

It took until the second business day of the new year for the chips to start falling in the US printed circuit laminate industry. On the same day, Isola changed hands, and Park Electrochemical announced it was reviewing options for its PCB unit – a move generally seen as a precursor to a sale.

As the East Coast braced for a winter blizzard of epic proportions, Park Electrochemical sent a cold shiver down the spines of more than a few industry observers with its announcement of a “strategic evaluation” of its core printed circuit materials business, one that could spell the end of one of the last domestic manufacturers of FR-4 in North America.

Park has been paring its PCB operations over the past few years amid declining revenues and tighter margins. Even as the firm’s aerospace revenues have grown, overall Park sales have fallen year-over-year in 10 of the past 11 quarters, more than half the time by double digits. And said PCB revenues have been falling despite a rebound in the overall bare board market.