Features Articles

Mike BuetowThe question – actually, it was more of a plea – was to the point: How are fabricators handling first article inspection requirements?

Confusion, the writer pointed out, appeared to be growing throughout the supply chain, as it attempts to sort out just how often FAI needs to be performed.

It’s a fair question. Inspection is time-consuming (and thus expensive) and considered in many quarters to be non-value-added. And that’s not just for manufacturers but also customers, which face both additional evaluations and a data avalanche. That avalanche is the result of the surge in acceptable quality limit (AQL) samples of FAI measurements as supplied to the customer, which then must enter, sort and distribute (as needed) all that data. It is one thing to impose requirements on suppliers, but in the case of AS9100D, those requirements might be backflowing.

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Will ASICs and memory be packaged side-by-side?

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Clive AshmoreA new dispensing system facilitates loading 500g containers.

Your mother always told you not to drink from the milk carton or eat from the peanut butter jar. But, as far as you were concerned, consuming directly from the container was a far more efficient approach. The germ factor notwithstanding, turns out you might have been right! Who knew your insight might lead to innovation in material management for screen printing?

All joking aside, eliminating process steps and reducing the chance for error introduced with manual operations generally results in more efficiency and higher quality output. This is most certainly the situation when supplying material for the printing process. As you are aware, my mantra of “good inputs = good outputs” is the basis for high-yield printing. In the case of paste management, ensuring proper volumes of paste in front of the squeegee blade at all times exponentially increases productivity, optimizes output and reduces defects related to insufficient material. Putting down material automatically, as opposed to manually, saves cost, reduces line downtime and eliminates errors.

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Roy AkberAn overview of the multilayer PCB fabrication process.

The actual process of PCB fabrication can begin on receipt of the necessary documentation from the designer. These data include the choice of materials for the substrate and cladding, the number of layers and stackup, the mechanical layout, and the routing. The documentation must provide individual details for each layer of the PCB.

Preparing the central panel. The fabrication process starts with obtaining the copper-clad substrate. For a multilayer board, copper will be on both sides of the substrate, which forms the innermost or central layer. Usually, such copper-clad substrates are supplied in sizes of standard dimensions, with the panel sized to match the specific mechanical layout. Otherwise, the fabricator will resize the panel the necessary dimensions by means of a shearing process. Depending on the size and total number of discrete PCBs to be made, the panel may be dimensioned to contain multiple PCBs: An 18" x 24" panel might, for instance, contain four 4" x 4" PCBs. The copper cladding is usually provided with a thin layer of protective coating to protect the surface from oxidation. This protective layer must be removed by immersing the panel in a weak acid bath.

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David BernardSimple 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.

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Martin WickhamFor 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.




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