Failure Analysis Cases Studies on Solder De-Wetting for Electronics Products


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Editor’s note: This article/paper was presented at IPC APEX EXPO 2021 and was published in the Proceedings.

Abstract
Over many years defect analysis has been used at the company to determine the root cause of various defects experienced in the field on electronic products from customers. Based on this work, it has been found that around 25% of all case studies have been due to de-wetting issues. 

De-wetting is an issue with the solder joint where the molten solder and the substrate/component repel each other during the soldering process. Due to this, a very weak or no intermetallic bond is formed at the interface after reflow leading to defective and unreliable solder joints. 

Case studies in this area will be reviewed based on root cause analysis and countermeasures to prevent these defects. These case studies are related to inferior component/board plating quality, contaminated plating on both the PCB as well as the component, foreign object debris (FOD) as a cause of the de-wetting of solder, damaged component plating, and improper off-set solder paste printing. The results of the failure analysis are reported. 

Introduction
Electronics products are generally reliable. On occasion, defects occur during the manufacturing process which require determination of root cause to improve manufacturing yield and reliability. These defects are sent out to failure analysis laboratories or analyzed internally at the manufacturing company.

Solder paste material suppliers are contacted on occasion to provide input into a soldering defect for root cause analysis. Over many years defect analysis has been used at the company to determine the root cause of various defects experienced in the field on electronic products from customers.

Reviewing the various defect causes, it was found that around 25% of all case studies have been due to de-wetting issues. The following sections will review a series of case studies related to de-wetting issues based on root cause analysis with input provided on countermeasures to prevent these defects based on the company’s knowledge and experience in this area. These case studies are related to inferior component/board plating quality, contaminated plating on both the PCB as well as the component, foreign object debris (FOD) as a cause of the de-wetting of solder, damaged component plating and improper off-set solder paste printing.

Experimental
Electronic product from different customers was analyzed. All five cases investigated showed solder de-wetting. The five different de-wetting case studies were classified into the following categories which are then discussed in further detail: 

  1. Inferior board plating/surface finish quality
  2. Contaminated plating
  3. Foreign object debris (FOD)
  4. Damaged plating  
  5. Improper process condition setting  

To read this entire article, which appeared in the June 2021 issue of SMT007 Magazine, click here.

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