Soldering Process Technology

A Multinational Networking OEM was in the process of launching a new product, which was dissimilar to their standard products. The design was fast-tracked through an incomplete manufacturing review process, which excluded review by the Global Manufacturing Team, which resulted in the product utilizing a non-standard, non-recommended PCB surface finish. During pre-production builds, a test phenomena was identified that illustrated an inconsistent pass/fail pattern, whereby an assembly would pass test and subsequently fail the same test some period of time later.

Destructive failure analysis highlighted a fracture in close proximity to the PCB surface finish.

The EMS Provider and the OEM Manufacturing Support Team could not identify the root cause, concentrating their efforts on process improvements to try to optimize their electronic manufacturing processes to accommodate the PCB surface finish. After several weeks without resolution, and with the product launch deadline fast approaching, the Global Manufacturing Team was consulted.

As Global Equipment Engineer for Soldering Process Technology, I correctly identified the failure mechanism as “Black Pad” or Brittle Intermetallic Failure, whereby a PCB surface finish hyper-corrosion leads to a catastrophic interconnect failure.

Within hours, a resolution action was recommended and implementation had begun, with an additional rework option suggested that could be used to recover PCB stock of up to $3m value. Implementation of the recommended resolution eliminated the surface finish in question and all subsequent builds were found to exhibit no incidents of the catastrophic failure mechanism.

The New Product Introduction of this groundbreaking networking device was launched to consumers on time with zero surface finish related defects.

The history of the Black Pad or Brittle Intermetallic Failure mechanism is littered with claim and counter claim as to the root cause, how PCB processing impacts the occurrence of the failure mechanism and processing equipment and process chemistry conditions that contribute to the occurrence frequency. However, what is known is that the failure mechanism is almost exclusively attributed to a single surface finish and is mutually exclusive to certain surface finish choices.

Rather than tackle the complexities of the failure mechanism, the surface finish change was instigated to successfully exclude the occurrence of the failure mechanism.

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