Whether round or rectangle, HDI will be required to meet the needs of next-generation semiconductor nodes.

Can the electronics industry influence global trade pacts with China? And should it? The word from many major trade groups appears to be “yes” and “maybe not.”

IPC, SEMI, the Semiconductor Industry Association and National Association of Manufacturers have each commented of late on the proposed tax hikes to be levied by the US on Chinese imports in response to concerns over China’s technology transfer policies and the massive trade imbalance between the world’s two largest economies.

As most readers know, statistical tests calculate a mean and confidence intervals on the mean. We are all familiar with the fact that as our sample size decreases, our knowledge of the “true” mean becomes less and less certain. This is important for tests that use the mean, such as the t-test and ANOVA.

FIGURE 1 is an example of two data sets: “apples” and “oranges.” In the first experiment we had 15 samples of apples and 15 samples of oranges. Plotting the means with their calculated confidence intervals shows we cannot differentiate between apples and oranges. (Since the confidence intervals overlap, we cannot be certain both means are not equal.)

Why print offsets occur and how to correct them.

Printing offsets – the degree to which a material deposit is off center from the pad – can occur due to three primary elements of printing: the printed circuit board (substrate), the stencil and the printer. Each has to be manufactured and is surrounded by a process bandwidth, each with its own tolerances that can accumulate. Add to this the variables from different manufacturing methods, sites and base materials and, well, offset inevitability becomes obvious.

Let’s begin with the board and stencil. Gerber data is king; it’s where the designs begin and is the blueprint for PCB and stencil manufacture. Simply put, Gerber is an x, y coordinate and angle for a certain feature size and shape. When an offset occurs, it is the difference between what the Gerber says and what is actually produced. At the PCB level, the offsets derive from the artwork, the subtractive chemical process and the FR-4 laminate. Each of these has the potential for variability, as in the case of FR-4 that can stretch and move during temperature processing, because the coefficient of thermal expansion (CTE) is relatively poor, especially considering today’s dimensions. Given these realities, the board could be off in one corner, or it could be a gradual movement from the left corner to the right, from the center outward or just focused in one area of the board.