PCB News - HDI circuit board first-order and second-order production process

HDI circuit board first-order and second-order production process

1. HDI circuit board//////After pressing once, drill holes == "Press the copper foil again on the outside == "Laser again --- "First order
2. The HDI circuit board is pressed once and then drilled == "The copper foil is pressed again on the outside == "Laser again, and the hole is drilled == "The copper foil is pressed again on the outer layer == "Laser again ---" Second order.
It mainly depends on how many times your laser has been shot, that is, how many orders.
Here is a brief introduction to the HDI circuit board process of the PCB board. Basic knowledge and production process With the rapid changes in the electronics industry, electronic products are developing towards lightness, thinness, shortness, and miniaturization. The corresponding printed circuit boards are also facing the challenges of high precision, thinning and high density. The trend of printed boards in the global market is to introduce blind and buried vias into high-density interconnect products, thereby saving space more effectively and making the line width and line spacing finer and narrower.
One. HDI defines HDI: short for highDensityinterconnection, high density interconnection, non-mechanical drilling, micro-blind hole ring is less than 6mil, inner and outer layer wiring line width/line gap is less than 4mil, and the pad diameter is not greater than 0.35mm. The multilayer HDI circuit board manufacturing method is called HDI circuit board.
Blind via: short for Blindvia, which realizes the connection between the inner layer and the outer layer. Buried via: short for Buriedvia, which realizes the connection between the inner layer and the inner layer. The blind hole is mostly 0.05mm~0.15mm in diameter. The small holes and buried blind holes are formed by laser drilling, plasma etching and photo-induced drilling. Laser drilling is usually used, and laser drilling is divided into CO2 and YAG ultraviolet laser (UV).

Two. HDI circuit board sheet

1. HDI circuit board materials have RCC, LDPE, FR41) RCC: short for Resincoatedcopper, resin-coated copper foil. RCC is composed of copper foil and resin whose surface has been roughened, heat-resistant, anti-oxidation, etc., and its structure is shown in the following figure: (Used when thickness> 4mil) RCC resin layer, with FR-4 bonding sheet (Prepreg) Same processability. In addition, it is necessary to meet the relevant performance requirements of the multilayer HDI circuit board of the build-up method.
(1) High glass transition temperature (Tg);
(2) Low dielectric constant and low water absorption;
(3) It has higher adhesion and strength to copper foil;
(4) High insulation reliability and microvia reliability;
(5) The thickness of the insulating layer after curing is uniform and at the same time, because RCC is a new product without glass fiber, it is conducive to laser and plasma etching treatment, and it is conducive to the lightweight and thinning of the multilayer board.
In addition, the resin-coated copper foil has thin copper foils such as 12pm and 18pm, which is easy to process. 2) LDPE: 3) FR4 sheet material: used when thickness <=4mil. When using PP, generally use 1080, try not to use 2116 PP2. Copper foil requirements: when the customer has no requirements, the copper foil on the substrate is preferred to use 1OZ in the traditional PCB inner layer, the HDI board is preferred to use HOZ, and the inner and outer electroplated copper foil is preferred. Use 1/3OZ.
Three. HDI circuit board laser hole formation: CO2 and YAGUV laser hole formation The principle of laser hole formation: laser light is a powerful light beam excited by increasing energy when the "ray" is stimulated by external sources, among which infrared light or visible light With heat energy, ultraviolet light also has chemical energy. When it hits the surface of the work, there will be three phenomena: reflection (Refliction), absorption (Absorption) and penetration (Transmission), of which only the absorbed will have an effect. And its effect on the plate is divided into two different reactions: photothermal ablation and photochemical cracking.
1. YAG's UV laser hole formation: It can gather tiny beams, and the copper foil has a relatively high absorption rate. It can remove the copper foil and can be burned to micro blind holes below 4mil. When forming holes with CO2 lasers, resin will remain at the bottom of the hole. There is basically no resin remaining than the bottom of the hole, but it is easy to damage the copper foil at the bottom of the hole. The energy of a single pulse is small and the processing efficiency is low. (YAG, UV: Wavelength: 355, the wavelength is quite short, it can process very small holes, which can be absorbed by resin and copper at the same time) No special windowing process is required. 2. CO2 laser hole formation: using infrared CO2 laser machine, CO2 cannot be absorbed by copper, but it can absorb resin and glass fiber, generally 4-6mil blind holes.
The hole forming method of HDI circuit board is as follows:
A. Conformal Mask is to open the copper window method by pressing the RCC on the inner core board and then opening the copper window, and then using laser light to burn out the substrate in the window to complete the micro blind hole. The details are to first make the inner core board of FR-4, make it have blackened circuits and targets (TargetPad) on both sides, and then press it, and then remove the corresponding copper skin according to the copper etching film to remove the blind hole position and then use CO2 laser The resin in the window can be burned out, and the bottom pad can be hollowed out to form a micro blind hole. (The size of the copper window is the same as the blind hole.) This method was originally a patent of "Hitachi," and the general industry may have to be careful of legal issues when shipping to the Japanese market.
B. Large copper window method LargeConformalmask The so-called "large window method" is to enlarge the copper window to about 1 mil larger than the blind hole on one side. Generally, if the aperture is 6 mils, the large window can be opened to 8 mils. Our company uses this method for operation.
Four. The laser drilling blind buried hole operation process is explained with 1+2+1 as an example
Production process: cutting material - opening large copper windows - drilling L2~L3 buried holes - removing slag - electroplating buried holes - resin plug holes - - inner layer graphics - pressing - L1-2&L4-3 Layer LargeWindows (copper window is 1 mil larger than the blind hole diameter on one side) (etching)-L1-2 & L4-3 layer laser drilling blind holes-removing slag twice-plating blind holes (pulse plating)- Resin plug hole-grinding plate + copper reduction-mechanical drilling through hole-normal process 2+4+2 process opening - L3~6 layer graphics - pressing - opening large copper window - L23&L76 layer Laser buried hole - L26 Mechanical Drilling-Desmear-Plating Buried Hole-Resin Plug Hole-L2, L7 Layer Pattern-Pressing-Opening Large Copper Window-L12&L87 Layer Laser-Desmear---Plating Blind Hole---Resin Plug Hole- -Grinding board + copper reduction-mechanical drilling-normal process