PCB News - Understand the X-order HDI board

Understand the X-order HDI board

When a hardware engineer first comes into contact with a multilayer PCB, it is easy to see dizziness. It is usually ten and eight layers, and the lines are like spider webs.

In other words, three-dimensional graphics are used to display the internal structure of PCB diagrams of various stacked structures.

Is it simple and straightforward?

The wire processing of multi-layer PCB is no different from single-layer and double-layer. The biggest difference is the process of passing through the holes.

The circuit is etched, the hole is drilled, and then copper plated. These are all known hardware developments, so don't repeat them.

Multilayer circuit boards usually include through-hole boards, first-order boards, and secondary stacked orifice boards. For high-end circuit boards such as third-order boards, any layer of interconnection boards are usually rarely used, and theft is expensive, and there is not much discussion.

In general, 8-bit single-chip products use 2-layer through-hole boards, 32-bit single-chip-level intelligent hardware, 4-layer and 6-layer through-hole boards, linux and android-level intelligent hardware, and 6-layer through-hole to 8-layer first-level hdi boards.

Compact products such as smartphones usually use 8-layer to 10-layer second-order circuit boards. Qualcomm 624 8-layer 2-level stacking hole There is only one hole from Kongdu Building to the fourth floor.

This hole is perforated whether it is the outer line or the inner line. It is called an orifice. The number of orifice plates has nothing to do with the number of layers. Usually two layers are through the orifice plate, and many switches and military circuit boards are made of 20 layers or through holes.

Drill through the circuit board with a drill bit, and then electroplate copper in the hole to form a channel. It is important to note that the inner diameter of the through hole is usually 0.2mm, 0.25mm and 0.3mm, but on average 0.2mm is much more expensive than 0.3mm.

Because the drill bit is too thin, it is easy to break, so the drill is slower. The time and cost of the drill bit is reflected in the increase in the price of the circuit board.

The six-layer first-order HDI board has a laminated structure. The two layers on the surface are laser holes, the inner diameter is 0.1mm, and the inner layer is mechanical holes. It is equivalent to a 4-layer orifice plate, plus 2 layers, covered on the outside.

The laser can only penetrate the glass plate, not the metal copper. Therefore, drilling on the outer surface will not affect other linings. After the laser hits the hole, it enters the copper plating layer, and then the laser passes through the hole.

It is a 6-layer 2-step staggered HDI board. Usually we use 6 layers, 2 layers less, most of which are 8 layers, 2 steps. There are more layers here, the same as 6 layers.

The so-called second level has two layers of laser holes. The so-called staggered holes means that the two layers of laser holes are staggered. Why should they be staggered? Because the copper plating is not satisfactory, the hole is empty, so you can't directly punch the hole above, you have to stagger a certain distance, and then hit a layer of empty. The second step of the sixth floor is the second step of the fourth floor, and the second floor is the first step of the fourth floor.

The second order of the eighth floor is the first order of the six floors, and the first order of the sixth floor plus two floors. The two layers of laser holes on the staggered board overlap, and the lines will be more compact. The inner laser hole needs to be electroplated, and then the outer laser hole is made.

The price is more expensive than the wrong hole. In other words, each layer is a laser hole, and each layer can be connected together. How do you want to go, how do you punch holes.