Oct03
What Causes Wave-Like Wrinkles or Cracks in Solder Joints After Reflow?

post on October 3, 2024

What Causes Wave-Like Wrinkles or Cracks in Solder Joints After Reflow?

These soldering wrinkles appeared quite a while ago, but Workingbear recently came across a similar situation on an online forum. Thinking others might encounter the same issue, I decided to document it for both personal reference and to share with everyone.

Workingbear had previously noticed that some data transmission cable samples from a supplier had solder joints on the internal PCBA with wave-like wrinkles and what looked like cracks. At first, it was assumed that these were caused by cracked flux residue. However, even after cleaning the flux with alcohol, the same wave-like wrinkles were still visible, indicating that the issue was actually with the solder itself.

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Process, Quality, SMT, Soldering, Uncategorized     WorkingBear    Views (134)     comment (0)
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Sep26
The Role of Immersion Gold and Electroplated Gold in PCB Soldering

post on September 26, 2024

The Role of Immersion Gold and Electroplated Gold in PCB Soldering

Workingbear previously wrote an article about how insufficient gold thickness in the ENIG surface treatment of a PCB led to the oxidation of Electroless Nickel, weakening solder joints and causing components detachment during plug and unplug. However, many sources explain that gold’s primary role in PCB surface finishes is to prevent nickel oxidation by acting as a barrier. Gold (Au) doesn’t strengthen  solder joints and may form brittle intermetallic compounds (IMCs) like AuSn and AuSn2, leading to gold embrittlement.

Recommended reading: Two Major Potential Problems with ENIG PCB Pads (Black Nickel and Phosphorus-rich Layers) and Preventive Measures

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PCB/FPC/PTF, Quality, SMT, Soldering, Uncategorized     WorkingBear    Views (386)     comment (0)
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Sep19
Does the Gold Thickness in ENIG PCBs Affect Component Detachment?

post on September 19, 2024

Does the Gold Thickness in ENIG PCBs Affect Component Detachment?

The solder pads at the site where the component fell off show signs of black pad discoloration, and most of the pads were pulled off with the component and are still attached to the component leads. It is speculated that the detachment occurred at the Electroless Nickel (EN) layer or the phosphorus-rich (P-rich) layer."

Do you know how the thickness of the gold layer in ENIG surface-finished PCBs impacts soldering quality? What role does the gold layer play in PCBA soldering? How could the detachment of electronic components from a PCB be related to the gold thickness in ENIG? Should the gold layer be as thick as possible?

For a while, the SMT contractor managed by Workingbear got into a dispute with the PCB manufacturer. Both parties were debating the gold thickness specifications for ENIG (Electroless Nickel Immersion Gold) surface-finished PCBs. The issue arose because the EMS (Electronic Manufacturing Services) factory recently used a batch of ENIG PCBs, and during the final assembly after surface mount and board-level testing, components were found detaching from the PCB. Initially, the SMT factory strongly believed that the detachment was caused by the “black pad” issue commonly associated with ENIG. From the appearance, the pads where the components had detached showed the characteristic black pad color. Most of the pads had come off the board entirely, sticking to the component leads. The theory was that the solder fracture might have occurred at the Electroless Nickel (EN) layer or the phosphorus-rich (P-rich) layer.

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PCB/FPC/PTF, Quality, Reliability, SMT, Soldering     WorkingBear    Views (159)     comment (0)
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Sep12
What Are Hard Gold, Soft Gold, Plated Gold, ENIG, and Flash Gold in PCBs?

post on September 12, 2024

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In the electronics industry, “gold” is often used on the surface of products. But do you know what hard gold, soft gold, electroplated gold, ENIG (Electroless Nickel Immersion Gold), and flash gold are in printed circuit boards? What are the differences between them, and what should be considered in their applications?

Workingbear wants to clarify that the information shared in this article is based solely on personal experience and knowledge. Since I haven’t worked directly in the PCB manufacturing industry, my understanding of hard gold, soft gold, and flash gold comes from years of interacting with PCB manufacturers and asking questions. If you notice any mistakes, please feel free to point them out.

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PCB/FPC/PTF     WorkingBear    Views (772)     comment (0)
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Sep05
Using 2D X-Ray to Diagnose BGA Solder Void Issues

post on September 5, 2024

Using 2D X-Ray to Diagnose BGA Solder Void Issues

This is an X-ray inspection image of an MCU’s BGA soldering that failed after reflow. The owner mentioned that the BGA package was not functioning, but when pressing on the MCU, it would temporarily work again. Since Workingbear didn’t have the chance to see the faulty product in person, the assessment is based on this image alone. However, from the overall description given, this appears to be a typical case of BGA non-wetted. Can you spot the problem with the solder balls from the X-ray image above?

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Quality, SMT, Soldering, Test/Inspection     WorkingBear    Views (555)     comment (0)
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