It’s cheaper and faster to inspect by machine over microsection.

Most of my columns have attempted to discuss the “typical,” and often more obvious, solder joint failures that can be seen using x-ray inspection. This is usually the main and most important function of this type of analysis.

Nondestructive inspection of cracks within solder joints or components is also desirous, however, but this is much more difficult to evaluate optically or by x-ray. Even for those joints that are not optically hidden, optical inspection for cracks is likely limited to the very end of the termination and requires a mostly edge-on view at a reasonable magnification (FIGURE 1) to have the best chance of seeing a crack failure. When inspecting fully populated boards, achieving this level of magnification and orientation may be difficult to do optically, and any cracks present will need to be distinct by showing a separation in the joint. If the two halves of the cracked solder are still touching, then analysis may be almost impossible to make. Furthermore, such a crack will be at the end of the termination and not necessarily extending further back into the joint – for example, into the heel fillet of a QFP, which is more crucial to joint integrity. This may mean a cosmetic issue is seen on one joint, and the actual fault may remain hidden elsewhere.

Changes in purchasing and line practices can save big dollars.

The benefits of implementing Lean manufacturing philosophy are higher throughput and elimination of the variation that can introduce defects into a process. In a static environment, implementing Lean philosophy creates significant efficiencies that stay in place with little oversight. Most electronics manufacturing services (EMS) providers have very dynamic environments, however, where supply chain, customers, project technologies, volumes, production personnel and factory floor layout change frequently. In that environment, inefficiencies can creep in. Six Sigma training provides employees with a formalized product-solving methodology that allows these inefficiencies to be corrected. SigmaTron in Tijuana, Mexico, uses Six Sigma as a tool to keep its team focused on eliminating inefficiencies. The facility faced three major challenges over the past year: changing dynamics in the materials market; more projects moving to Mexico for tariff mitigation; and spikes in demand at existing customers for their products. This column looks at four Green Belt projects that cumulatively have eliminated nearly $300,000 in unnecessary costs in the first five months of improvement implementation.

Are you vacuuming the right way?

This month we see a solder paste print deposit with what appears to be migration of paste particles away from the main pad. If this is just a one-off, a careful wipe with acotton bud would avoid an unnecessary wash-off and reprint. Ensure the PCB surface finish can withstand a wash-off process; some surface finishes don’t like it. Wash-off can affect wetting and final solderability.

A few reasons for this defect, each of which could be the root cause:

• Double printing or excess squeegee pressure
• Solder paste contamination on the bottom of the stencil from a previous print
• Misplaced or missing component
• Vacuum hold-down of PCBs during printing with exposed vias under BGAs.
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And does your purchasing department know what to send, and what not to?

Many commercial EMS and OEM companies have a gaping hole in the system to protect the intellectual property (IP) of their customers.

I can’t count the number of emails from customers requesting a quote for a printed circuit board that include not only the Gerber file(s) for that PCB, but also the assembly drawing, the bill of materials, and the schematic drawing for the entire product.

Companies in our industry take a number of steps to protect customer IP. They require signed nondisclosure agreements for all involved in the manufacture of their PCBs. They verify the identity of any visitors to their secured US manufacturing facilities and assign outsiders mandatory escorts. They may ban cellphones or any other devices that could be used to record inside those facilities.

However, with a press of the Send button, all that IP protection goes out the door.