When hardware engineers first touch multilayer PCB, it is easy to look dizzy. Often ten layers or eight layers, the line like a spider web.
Another way to think about it is to use three-dimensional graphics to show the internal structure of various stacked PCB diagrams. That's easy to understand.
The most important part of the HDI board is the Vias.
Multilayer PCB line processing, and single-layer and more-layer no difference, the biggest difference in the process of hole.
Lines are etched out, through the hole is drilled and then copper plating out, these do hardware development everyone understand, do not go into details.
Multilayer circuit board, usually through the hole plate, the first order plate, the second order plate, the second order stacked hole plate.Higher order such as the third order board, any layer of interconnection board is usually used very expensive, not much discussion.
In general, 8 bit microcontroller products with 2 layers of through-hole plate;32-bit MCU level intelligent hardware, using 4 layers and 6 layers of through-hole plate;Intelligent hardware of Linux and android level, using 6 layer through-hole to 8 layer 1-order HDI board;Compact products like smartphones typically use 8 layer to 10 layer 2-order HDI board.
8 layer 2-order HDI ，Qualcomm snapdragon624
The most common through hole
There is only one type of hole, from the first to the last.No matter the external line or the internal line, the hole is perforated.It's called a through-hole plate.
Through the hole plate and the number of layers does not matter, usually everyone use 2 layers are through the hole plate, and many switches and military circuit board, do 20 layers, but it is still through the hole.Learn more Pls inquiry RayMing Technology at www.raypcb.com
The circuit board is drilled through with a bit and copper plated into the hole to form a path.
It should be noted here that the inner diameter of the through-hole is usually 0.2mm, 0.25mm and 0.3mm, but generally the 0.2mm is much more expensive than the 0.3mm.Because the drill bit is too thin and easy to break, the drilling is slower.More time and the cost of the drill bit, reflected in the price of the circuit board on the rise.
The laser hole of HDI board
This picture is the laminated structure diagram of the 6 layer 1-order HDI board. Both layers on the surface are laser holes with an inner diameter of 0.1mm.The inner layer is a mechanical hole equivalent to a 4-layer through-hole plate, and the outer layer is covered with 2 layers. The laser can only penetrate the glass fiber plate, but not the metal copper. So the perforation of the outer surface does not affect the other internal wiring.Laser perforation, and then to copper plating, the formation of laser through the hole.
2-order HDI board, Two sets of laser holes.
This is a 6 layer 2 - order staggered HDI plate.At ordinary times, people use 6 layers and 2 levels less, most of them are 8 layers and 2 levels.In this case, the number of more layers is the same as the number of layers. The so-called 2-order laser hole means that there are two sets of laser holes.Why stagger them?Because plating copper plating dissatisfaction, the hole is empty, so can not directly above the hole, to stagger a certain distance, Then make a layer of laser holes.
6 layer 2-order HDI=4 layer 1-order HDI+2 layer
8 layer 2-order HDI=6 layer 1-order HDI+2 layer
Stack hole plate, the technology is complex and the price is higher.
The two laser holes of the staggered orifice plate are overlapped to make the circuit more compact.The inner laser hole needs to be electroplated and filled, and then the outer laser hole needs to be made.The price is more expensive than staggered holes.
Super expensive any layer interconnect board, multi-layer laser stack.
Each layer is a laser hole, and each layer can be connected together.You can run a wire as you want, and you can drill a hole as you want.
but more than 10 times more expensive than the common through-hole plate!
Therefore, only the iphone is willing to use.Other mobile phone brands, who has not heard of any layer of interconnect board.
Let's put a picture at the end and compare it again. Please pay attention to the size of the hole and whether the welding pad of the hole is closed or open.
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