How to distinguish HDI circuit board is several levels of blind buried?

1. Press one time after drilling == "outside again press copper foil ==" and then laser -------- "first order

2. Press one time after drilling == "outside again pressed copper foil ==" then laser, drilling == "outer layer again pressed copper foil ==" then laser ------- "second order.

The first is to see how many times you are laser, is a few steps. The following is a brief introduction of the PCB board HDI circuit board process. As the electronic profession changes with each passing day, electronic products towards light, thin, short, miniaturized open, the corresponding printed board is also facing high precision, fine line, high density. The trend of printing board in global shopping malls is to introduce blind and buried holes in high-density interconnected products, and then more useful space saving, so that the line width and line spacing are thinner and narrower.

one, HDI definition

HDI: Short for high Density interconnection, high density interconnection, non-mechanical drilling, micro blind hole ring less than 6mil, internal and external layer wiring width/gap less than 4mil, pad diameter is not greater than 0.35mm of the increased layer method of multilayer plate manufacturer is called HDI board. Short for Blind via, a buried hole that completes the connection between the inner and outer layers: Buried via is short for Buried via. Blind access holes are mostly 0.05mm~0.15mm in diameter to complete the connection between the inner and inner layers. Laser hole formation is generally used for blind hole formation, including laser hole formation, plasma etching hole and photoinduced hole formation, which can be divided into CO2 and YAG ultraviolet laser machine (UV).

two, HDI circuit board

1.HDI circuit board material includes RCC,LDPE,FR41)RCC:Resin coated copper. RCC is composed of copper foils and resins that have been roughened, heat-resistant and oxidation-resistant on the outside, (thickness > 4mil) RCC resin layer, has the same process as FR 4 adhesive sheet (Prepreg).

In addition, it is also necessary to satisfy the functional requirements of the laminated multilayer, such as: (1) high insulation reliability and micro-through hole reliability; (2) high glass transition temperature (Tg); (3) Low dielectric constant and low water absorption; (4) Higher viscosity and strength of copper foil; (5) The insulating layer thickness is uniform after curing, because RCC is a new product without glass fiber, which is conducive to laser and plasma etching treatment, and is conducive to lightweight and thinning of multilayer board. In addition, resin coated copper foil with 12pm, 18pm and other thin copper foil, simple processing.

2, FR4 sheet material: thickness < =4mil. 1080 is generally used when using PP, and try not to use PP2 of 2116. Copper foil requirements: When the customer has no requirements, copper foil on the substrate is preferred to use 1 OZ in the inner layer of the transmission PCB circuit board, HDI circuit board is preferred to use HOZ, internal and external electroplated copper foil is preferred to use 1/3 OZ.

Three. Laser pore-forming :CO2 and YAG UV laser pore-forming principle of laser pore-forming: laser light is a powerful beam of light stirred up by the increase of energy when the "ray" is affected by the outside, in which infrared light or visible light has thermal energy, and ultraviolet light has chemical energy. The ejection onto the surface of the plant will entail reflection-absorption and Transmission, the effects of which will occur only to those who are being absorbed. And its effect on the plate can be divided into two different reactions: photothermal ablation and photochemical cracking.

1.YAG's UV laser pore-forming: it can set a fine light beam, and the copper foil absorption rate is relatively high, it can remove the copper foil and burn the micro blind hole below 4mil. Compared with CO2 laser pore-forming, there will be no resin residue in the bottom of the hole, but it will simply damage the copper foil at the bottom of the hole, the energy of a single pulse is little, and the processing power is low. (YAG, UV: wavelength: 355, wavelength is appropriate short, can process very small holes, can be resin and copper together) do not need special window technology 2.CO2 laser hole: choose infrared CO2 laser machine, CO2 can not be absorbed by copper, but can absorb resin and glass fiber, generally 4~6mil micro blind hole.

The hole formation method is as follows:

1. The Conformal Mask of copper window opening is to press RCC on the inner Core plate, then open the copper window, and laser light to remove the substrate inside the window to complete the micro-blind holes. Details are to make the inner center plate of FR-4 first, so that both sides have blackened lines and Target Pad, and then press together, and then according to the corrosion of copper window film to remove the orientation of the blind hole corresponding copper skin and then CO2 laser light burned the resin in the window, can be hollowed out to the bottom pad and micro blind holes. (Copper window and blind hole size) This method was originally the "Hitachi Manufacturing" patent, general operators if they want to ship to the Japanese market, may have to be careful of legal issues.

2. The so-called "Large Conformal mask" is to expand the copper window to about 1mil larger than the blind hole. When the aperture of a prajna is 6mil, its large window can be opened to 8mil. 

Four. 1+2+1 is taken as an example to illustrate the manufacturing process: Cutting, Large copper Windows open, L2 ~ L3 buried holes -- -- -- -- -- in addition to the glue residue -- -- -- -- -- -- -- -- -- - plating buried hole - resin plug hole -- -- -- -- -- the inner graphics - pressing -- -- -- -- -- - L1-2 & Large L4-3 layer Windows (Copper window 1mil larger than blind hole aperture each side) (etching) ----- -- L1-2&L4-3 layers Laser drilling blind holes -- -- -- -- -- -- -- in addition to the glue residue twice -- -- -- -- -- -- -- electroplating blind hole (pulse electroplating) -- -- -- -- -- - resin plug hole -- -- -- -- -- -- -- grinding plate + reduce copper -- -- -- -- -- - mechanical drill hole is -- -- -- -- -- normal 2 + 4 + 2 processes and cutting L3 ~ 6 layer graphics - pressing - large copper Windows open →L23&L76 Laser buried hole →L26 mechanical drilling → rubber slag removal → electroplating buried hole → resin plug hole -----L2, About the big copper open window layer graphics - pressing - - L12 & L87 layer Laser - in addition to the glue residue - plating blind hole - resin plug hole - grinding plate + copper reduction - mechanical drilling - normal process