Discussion on the industry trend of circuit board PCB substrate

A, FR-4 sheet of continuous innovation
In short, the circuit board substrate including copper foil, resin and reinforcing material such as the three major raw materials. However, if further in-depth study of the existing substrate and look at the changes over the years, it will find the complexity of the content of the substrate is indeed difficult to imagine. Due to the increasingly stringent requirements of the circuit board manufacturers for the lead-free era of substrate quality, resulting in the performance and specifications of the resin and the substrate, will undoubtedly become more complex. The challenges encountered by the substrate supplier, is to find the best balance between the various needs of customers, in order to obtain the most economic production efficiency, and its product data provided to the overall supply chain as a reference.
Two, leading the industry trend of substrate specifications
A number of industry trends in the process, which will lead to the re formulation of the city and the use of these trends, these trends include multi laminate design trends, environmental regulations, as well as the demand for electricity, etc.:
1, the design trend of multi wide plate
Currently one of PCB design trends is to improve the wiring density, desire of this goal has three: first, cut the line width and distance, the unit area can accommodate more more intensive wiring; followed by an increase in the number of layers of the circuit board; finally, reducing the aperture and pad size.
However, when the unit area of the line more and more time, the working temperature is bound to rise. In addition, increasing the number of circuit boards, it is bound to make the completion of the synchronous plate thickness. Otherwise, it can only be matched with a thin dielectric layer to maintain the original thickness. PCB is thick, the hole wall caused by heat accumulation heat stress will increasingly increase, thus making the Z direction becomes larger thermal expansion effect. Selection of the thinner dielectric layer, it means that the rubber content more substrate and film must be used; but gum content of more, will cause through aperture Z direction of thermal expansion and stress to increase. Furthermore, reducing the through hole aperture, unavoidable and the aspect ratio becomes large; therefore, in order to ensure the plated through hole of reliability, the substrate must have lower thermal expansion and better thermal stability, not only lost by the wayside.
In addition to the above factors, when the circuit board assembly component density increased, then the layout of the guide holes will also be arranged more closely. But the move will make the situation more tense glass beam leakage, even in the hole wall between the glass fiber bridging phenomenon occurs, resulting in a short circuit. This anode of filamentous leakage phenomenon (CAF) is one of the lead-free era focused on board the theme, of course, a new generation of substrate must have better anti CAF ability, not only to a lead-free soldering in PinChu condition.
2, environmental protection laws and regulations
Environmental protection regulations for the substrate, in the political intervention has added a lot of additional requirements, such as the EU's RoHS and WEEE, and a number of directives, will affect the formulation of sheet specifications.
In numerous regulations, RoHS limits the lead content in welding. Tin lead solder in the assembly plant has been for many years, the melting point of alloy is 183 DEG C, and the welding process temperature is about 220 degrees celsius.
The mainstream of the lead-free solder tin silver copper alloy (such as the melting point of SAC305 is about 217 degrees Celsius, the peak temperature usually when welding will be as high as 245 degrees celsius. Welding temperature rise, represents the substrate must have better thermal stability to endure multiple welding caused by thermal shock.
The RoHS directive also disables some of the halogen containing flame retardant, including PBB and PBDE, etc.. However, PCB substrate in the most commonly used flame retardant of four TBBA two phenol, in fact, is not in the black list of RoHS. Nevertheless, due to containing TBBA plate in heating will produce inappropriate ashing reaction, resulting in some machine brands still consider changes to adopt halogen-free materials.
3, electrical requirements
High speed, broadband and wireless RF applications, force plate also has better electrical performance, i.e. dielectric constant DK and dissipation factor DF, not only must be suppressed and must be full board is stable, and should be properly prepared can be controlled. In accordance with these electrical requirements, but also had to be in the thermal stability of the inferior, the only way, its market demand and the share of the party to increase.
If you have  PCB to produce, please send Gerber to sales@pcbsky.com.cn .Thank you.


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