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Soldering in assembly might not be required

Friday, December 2, 2022

It seems that just about every year, the PCB assemblers encounter a new solder challenge as it moves to smaller, much more capable products with increased performance requirements. Ever smaller components, finer pitches, smaller pads, finer traces, and spaces on the PCB continue to challenge those companies tasked with building complex products with high yields and solid reliability. Although doable to a degree, we’re reaching the limit of what can be done efficiently and economically. An objective observer would quickly conclude that the industry cannot, and should not, continue down this path.

When we look at some of the most common causes of failure in an electronic product, solder is at the core.

In a traditional component assembly, a PCB is designed and fabricated, then components are attached using a solder paste. At that point, the entire assembly is subjected to intense heat as the PCB and components are thermally soldered to complete the assembly. Lots can go wrong during this process, such as: opens, insufficient solder, excessive solder, solder cracking, tin whiskers, poor wetting/dewetting, voids, blowholes, cold solder joints, brittle solder joints, head-on-pillow, graping, tombstoning, popcorning, solder balling, misregistration, insufficient cleaning under devices, incomplete solder joints, shorted solder joints, solder ball voids, solder ball shorts, overheated solder joints, cold solder joints, damaged solder pads, insufficient solder on joints, or through-holes.

Solder also has a spillover effect on PCB laminate material during the assembly process. These include: corner cracking, barrel cracking, post separation, hole-wall pullaway, resin recession, delamination, pad cratering, and decomposition.

Although solder defects are well known and fairly well managed, solder’s constraints on the industry have not been well understood.

Joe Fjelstad, a partner in the Occam Group and founder of Verdant Electronics, sums up the issue with an analogy: “There’s a reason why the Tour de France is not competed with training wheels on racing bikes. They would slow them down and make them less maneuverable. Inspection, test, and rework are the assembly industry’s training wheels.”

With all of solder’s constraints and limitations—which limit industry progress—it is time to ask: What would a world without solder be like?

If we didn’t have the restrictions that solder places on just about every aspect of an electronic product, what could we do? What are the possibilities—if we were to see solder’s days as numbered?

First, in that scenario, we would need one or more solutions that would remove it entirely.

At Occam, we have developed a process that supplants solder—and PCBs—with a new methodology for component assembly. We sometimes describe it as reverse order processing.

Our vision is to first attach components to a “component board” and test that assembly before encapsulation and circuitization. This ensures that all assemblies are known to be good at the outset. There are several methods for adding component connections, including traditional plating techniques and additive printed circuits (printed electronics).

By removing solder, thermal excursions are greatly diminished.

This solderless technology unlocks a lot of bottled-up product potential, removing the many constraints that product designers have had to work around for decades.

New opportunities include: lower overall product cost, higher reliability, smaller size and reduced weight, simpler designs with fewer layers using less expensive software with fewer re-spins, improved first-pass yield, improved environmental footprints, integral thermal management, EMI and ESD mitigation, new and improved architectural design potentials in the third dimension, and faster time to market.

Let’s take the training wheels off—and go solderless.

By: DocMemory
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