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The Impact of AL Surface Treatment on the Peel Strength between Rigid-Flex PCB

by: Dec 25,2018 593 Views 0 Comments Posted in Flexible PCB

Introduction:

Rigid-flex PCB is a new type of PCB which has both the durability of rigid PCB and the adaptability of flexible PCB. Of all types of printed circuit boards, rigid-flex PCBs are the most resistant to harsh application environments and are favored by manufacturers of medical and military equipment.

Compared with the common FR-4 rigid-flex substrates, the aluminum rigid-flex substrates have better heat dissipation performance and higher service life. The binding force of the PCB has a crucial impact on the reliability of the product, so it is necessary to study the surface treatment method of aluminum substrate, and then selecting a better binding force treatment method for production, which can improve the reliability of PCB, in order to meet the requirements of high reliability of electronic products.

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Some Common Surface Treatment Methods of Aluminum Substrates:

The surface treatment methods of aluminum substrates can be divided into physical grinding & brushing methods and chemical etching methods. The purpose of both methods is to form a certain roughness on the surface of aluminum substrate so as to increase the adhesion between the surface of aluminum substrate and the medium.

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Physical Grinding & Brushing Methods:

Physical grinding brush method is through grinding brush, sand belt or ash powder and plate contact, and apply a certain pressure, so that the plate surface with a certain roughness of the surface.

Common physical grinding brush methods are: nonwoven cloth grinding brush, volcanic ash grinding brush, sand belt grinding and other methods.

Chemical Etching Methods:

Chemical etching is through the reaction of solution and aluminum, which means that etching surface of aluminum substrate, so that the surface of aluminum substrate has a certain degree of roughness of the surface. Generally use alkaline solution, but because the aluminum itself is not resistant to strong alkali, so the need for operators in the actual operation of the process of strict control of the concentration of solution and reaction time.

Measurement of Surface Roughness of Aluminum Substrate:

The measurement methods of surface roughness can be divided into contact measurement and non-contact measurement.

The contact measurement method is mainly the contact needle method, which is the use of small diameter probe with larger reference plane slide gauge head, by applying small power, let the probe along the surface of the sample length of the object under test, resulting in a micro move up and down, and then through the transformation of magnetic sensor to get the corresponding shift data, can get all kinds of required roughness data.

Non-contact measurement is a method that indirectly reflects the information of the measured surface by means that has no influence on the surface topography. The biggest advantage of this kind of method is that the detection part of the measuring device does not contact directly with the measured surface, which protects the measuring device and avoids the measurement error caused by direct contact with the measuring device.

Conclusion:

(1) The roughness of aluminum plate surface treatment is not the larger the better, but also need to consider the surface treatment morphology and uniformity. The alkali etching surface treatment is the best, which can provide a uniform micro rough surface.

(2) Based on the above tests, the plate with alkali etching surface treatment technology before compression has high anti-aging performance and can provide the best adhesion force to ensure the high reliability of the end product.

(3) There are various surface treatment methods for aluminum plates. High-yielding, high-efficiency and low-cost surface treatment technologies are preferred in production, and composite surface treatment can be adopted when necessary to meet the requirements of high reliability of products.


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