FPC failure analysis, PCB stress and strain testing standards!

FPC is the abbreviation of Flexible Printed Circuit, also known as Flex, which is flexible printed circuit board.

Refers to a flexible printed circuit board that forms lines on copper foil based on PET or PI. It can properly carry a variety of active and passive components and accessories. Through proper assembly design, it is widely used. Interconnected in various modules of electronic products.

PCBA and FCP failure analysis, stress and strain testing solution provider: Xiangsheng 18588661846 (same number on WeChat).

Advantages of PC

(1) It can be freely bent, rolled, folded, laid out according to space, and moved and expanded in three-dimensional space to achieve the integration of component assembly and wire connection.

(2) The use of FPC can reduce the size and weight of electronic products, which is suitable for the development of electronic products in the direction of high density, thinness, miniaturization, and high reliability. Therefore, FPC is widely used in aerospace, military, mobile communications, notebook computers, and PDAs. , it has been widely used in product fields such as digital cameras.

(3) FPC also has the advantages of good heat dissipation, weldability, easy assembly, and low overall cost. The soft and hard combination design also makes up for the slight lack of the soft base material in the component load-bearing capacity to a certain extent.

Disadvantages of FPC

(1) High one-time initial cost

Since FPC is designed and manufactured for special applications, the cost of initial circuit design, wiring, film, and molds is relatively high.

(2) It is difficult to change and repair FPC

Once the FPC is made, changes must start from the negative drawing, so it is not easy to change. Functionally, short circuit defects cannot be repaired compared to the PCB hard board. 

(3) Easily damaged by improper operation 

Improper operation by assembly personnel can easily cause damage to the FPC, and its soldering and rework require trained personnel.

The main manifestations of FPC failure are mechanical stress causing cracking and failure of the soft board solder balls, and poor contact between the internal FPC board connecting boards.

Test methods and steps:

1. Select and paste the strain gauge: The strain gauge is a sensor that can linearly change the resistance value according to the magnitude of the stress. When the strain gauge deforms, the resistance value will change accordingly. Paste the strain gauge on the circuit that needs to be tested. on the board.

2. Connect the instrument: Connect the strain gauge lead to the test instrument of the test system, adjust the sampling frequency, filter value, gain setting, number of channels, configure the main channel and other parameters, and run the test program to check whether each channel is connected .

3. Measure strain: Place the circuit board on the process that needs to be tested, click Start, collect data, and then perform the actions of the corresponding process of the circuit board (screwing, splitting, ICT, etc.). After the action is completed, click to stop collection. Phone 18588661846=VX.

4. Issue a report: Import the collected data into the software, fill in the plate thickness and strain rate, and click on the production report to produce a stress test report (automatically generate a report with one click according to the IPC/JEDEC-9704 standard).

Any mechanical stress present during the board manufacturing process can be detected.