Production of blind buried plate
I. Overview :
Blind-buried orifice plates are mainly used for high-density, small-microplate production. The purpose is to save circuit space, so as to reduce PCB volume, such as mobile phone boards.
a). Laser drilling,
1. Reasons for drilling with laser:
a. Customer data requires laser drilling;
b Because the blind hole aperture is very small <=6MIL, laser is required to drill.
c, special blind buried holes, such as L1 to L2 have blind holes, L2 to L3 have buried holes, they must be laser drilled.
2. Principle of laser drilling:
Laser drilling is to use the plate to absorb the heat of the laser to vaporize or dissolve the plate into holes. Therefore, the plate must have absorbance. Therefore, the RCC material is generally non-reflective because there is no fiberglass cloth in the RCC.
3. Introduction to RCC materials:
RCC material is coated with resin copper foil:
By coating a rough surface of the electrolytic copper foil with a layer of resin with unique properties.
Three commonly used suppliers: Shengyi Company, Mitsui Company, LG Company
Material: Resin thickness 50 65 70 75 80 (um), etc.
Copper foil thickness 12 18 (um), etc.
RCC material has high TG and low TG material, and the dielectric constant is smaller than normal FR4. For example, Guangdong Shengyi's S6018 dielectric constant is 3.8, so pay attention when there is impedance control.
Other specific reference materials may be asked by the PE and RD departments.
4. Laser drilling tool manufacturing requirements:
A). It is difficult for the laser to burn through the copper skin. Therefore, before the laser drilling, it is necessary to etch the blind hole and complete the Cu Clearance with the aperture.
B). The laser drilling positioning mark is added to the L2/LN-1 layer and is indicated on the MI film modification page.
C). The etched blind spot film must be made of LDI, and the LDI plate size should be used for the material.
5. Production process characteristics:
A). When the total number of lines is N, the L2—Ln-1 layer is first made according to the normal board process.
B). After pressing the board, after the peripheral is finished, the process is changed to:
--->Drilling LDI positioning hole--->Dry film--->Erosion blind hole point--->Laser drilling--->Drilling through hole
--->Sinking copper----(normal process).
6. Other notes:
A). Since the RCC materials have not passed the UL certification, such boards are not marked with UL.
B). Regarding the structure of the slab on the MI, in order to avoid the use of such RCC-containing slabs as pseudo-layer slabs (because the film room is made of film pseudo-layer boards and normal boards), we are drawing the slab structure. Attention should be paid to the separation of the RCC material from the L2 or Ln-1 layers, such as the SR2711/01 row plate:
C).IPC-6016 is the HDI board standard:
Laser blind hole hole wall copper thickness: 0.4 mil (min).
Solder ring requirements: Allow tangency
If the PAD size is 5 mils or less larger than the aperture, it is recommended to add TEARDROP.
D). Board edge >=0.8”
b). Mechanical drilling blind / buried hole:
1. Scope of application:
Mechanical drilling can be considered when the size of the nozzle is >0.20mm;
2. Electroplating method for blind buried holes (refer to RD Notice TSFMRD-113):
A). Under normal circumstances, any layer of copper surface can only be plated +1 times for pattern plating;
B). Under normal conditions, after the completion of the full platen process, the plate thickness is >=80MIL, and the through hole is required.
Plating + graphic plating, therefore, the outer surface of the blind hole plating can not be plated.
C). After satisfying the above two conditions, the plating of the blind vias is carried out as follows:
I). When the outer line width is greater than 6 MIL and the through-hole thickness is less than 80 MIL, in blind via plating
The outer surface can be plated
II). When the outer line width is greater than 6 MIL, but the through-hole thickness is greater than 80 MIL, the outer surface of the blind-hole plating needs to be coated with a protective surface;
III). When the outer line width is less than 6 MIL and the through-hole thickness is >= 80 MIL,
In the blind hole plating, the outer surface of the plate needs to be covered with a film to protect the surface;
3. Ways of filming:
1) Blind hole aspect ratio <=0.8 (L/D)
When the outer panel is covered with a dry film, the whole plate is exposed, and the inner blind hole plate is plated,
2) When the blind hole aspect ratio is >0.8 (L/D), the outer surface of the outer surface is covered with a dry film blind hole exposure, and it is necessary to make an electroplating exposure film or LDI exposure, and the inner layer blind hole plate surface is plated.
4. Blind hole exposure method:
1) When blind holes <=0.4MM (16MIL), use LDI to expose blind holes,
2) When the blind hole is >0.4MM (16MIL), use the film to expose the blind hole.
5. Buried hole filming method:
1) When the line width of the buried surface is <=4 MIL, the buried plate surface needs to be exposed.
2) When the line width of the buried hole surface is >4 mil, the buried plate surface is plated directly.
1) In the aspect ratio L/D: L = dielectric thickness + copper thickness, D = blind hole / buried hole diameter.
2) Blind hole/buried hole plating film: * The diameter of the exposure point D = D-6 (MIL).
* Exposure point film plus point, its coordinates are consistent with the peripheral reference hole.
3) Blind holes that need to be filmed generally use pulse current (AC) during plating.
3. Some special requirements for blind hole plate:
1. Resin plug blind hole: When the buried hole size is large and the number of holes is large, when filling the plate, it needs a lot of resin to fill the buried hole. In order to prevent it from affecting the thickness of the platen, it can be resinized before the platen when required by R&D. The buried hole is pre-plugged, and the plug hole method should refer to the green oil plug hole.
2. When there is a blind hole in the outer layer,a. Because the outer layer will have glue out when the plate is pressed, a de-glue process is required after the platen;
b. Because the outer layer will clean the surface before the dry film, there is a grinding process, the chemical copper is very thin, only 0.05MIL to 0.1MI, so it is easy to wear off when grinding, so we will add a plate plating process, plus Thick copper.
The related processes are as follows: pressure plate - degumming - drilling - sinking copper - plate plating - dry film - graphic plating.
3. In addition, the PIN-LAM platen may be used when making a blind hole plate with a high number of layers, but it should be noted that only when the thickness of the CORE is less than 30 MIL, our machine can only use the PIN-LAM hole, for example: PR4726010, we use It is a common platen.
4. Regarding the edge of the blind hole plate, consider having multiple pressure plates and more process holes, so try to keep the edge of the plate to 0.8” or more.
5. When writing the LOT card, about the sub-process, that is, to write the layout structure of the single sub-process, and also write the layout structure of the main process in the special requirements, in order to facilitate the following process.