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FCQFN (FLIP Chip QFN) power IC is abnormal.
Quad Flat No Leads (hereinafter referred to as QFN) encapsulation type, because there is no need to lead to the four sides (Leads), so it has the advantages of small size, low cost, and good heat dissipation. Therefore The chip design gradually moves towards high computing and miniaturization. From the perspective of IC categories, including high-speed transmission ICs, power management chips, and Wi-Fi chips are all used for QFN technology. It is mainly used in wearable devices, handheld devices, and even electric vehicles.
What is FCQFN? The full name is FLIP Chip QFN, which is the QFN encapsulated. The electrical path of FCQFN is shorter than the general QFN, and the high frequency attenuation is smaller and the signal rises rapidly. It provides better electrical properties, so it has become a more advanced packaging form.
▲ Figure 1: Flip Chip QFN structure diagram
However, the form of QFN packaging, because of no Leads design, is more difficult to judge the weld status from the appearance of the appearance, and will generate doubts of welding quality. Line and structure are also complicated than traditional QFN, which in turn increases the risk of reliability such as welding CRACK.
How to find it correctly What about the abnormal point of FCQFN power IC? In this issue, the Yitter Primary School will share. How to use five steps in Yitter Laboratory to strip the cocoon to make the failure position, and quickly assist customers to find the product abnormal point.
▲ Figure 2: Yite Lab uses five steps to make FCQFN fail
Step 1: I-V electro-special measurement test
Confirm whether there is electrical abnormality in IC by I-V Curve measurement (Open/Short/Leak/HR)
Step 2: 2D x-ray view
When the electrical anomaly is confirmed, the package structure is then inspected by 2D X-ray to confirm whether there is any abnormality. This package structure drawing will also be used to confirm the position of the subsequent highlight stack drawing.
Step 3: Thermal Emmi positioning highlights
Without destroying the original appearance of the sample, the phase difference of Thermal radiation conduction at the fault point in Thermal EMMI (InSb) can be used to locate the bright spot, and the 2D X-ray structure diagram taken in the second step can be superposed to confirm the abnormal position (see Figure 3).
It is worth mentioning that Thermal Emmi can also detect the depth of the failure point of IC packaging, and the device function is presented at the PHASE value. The PHASE value of the normal DIE end of this case is 77.1, while the abnormal highlight conditions PHASE value is 78.5. Because the abnormal conditions PHASE value is quite close to the normal DIE end highlight PHASE value, it can be assumed that the abnormal position may be in the copper column There is a problem with the DIE side on this side instead of the copper column to connect the Lead side.
▲ Figure 3: Use Thermal Emmi to locate the highlight position (left), and make a stacked graph with 2D X-Ray to find out the possible abnormal point position
Step 4: 3D x-ray fault analysis
In order to confirm that the hypothesis was correct, the Appropriate laboratory further analyzed the abnormal position by 3D X-ray (Figure 4). The internal structure was cut one by one to show the different depths of each layer, and the abnormal point was first found in the layer of the chip.
▲图四:By 3D x-ray 进行断层分析,找出异常点是在哪一层
▲ Figure 5: SEM review, find a crack on the DIE side of the copper column (crack)