CN112165781B - Method for controlling back drilling stub of stepped hole of PCB - Google Patents
Method for controlling back drilling stub of stepped hole of PCB Download PDFInfo
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- CN112165781B CN112165781B CN202011173903.1A CN202011173903A CN112165781B CN 112165781 B CN112165781 B CN 112165781B CN 202011173903 A CN202011173903 A CN 202011173903A CN 112165781 B CN112165781 B CN 112165781B
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- drilling
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/0011—Working of insulating substrates or insulating layers
- H05K3/0044—Mechanical working of the substrate, e.g. drilling or punching
- H05K3/0047—Drilling of holes
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/09—Shape and layout
- H05K2201/09818—Shape or layout details not covered by a single group of H05K2201/09009 - H05K2201/09809
- H05K2201/09845—Stepped hole, via, edge, bump or conductor
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/02—Details related to mechanical or acoustic processing, e.g. drilling, punching, cutting, using ultrasound
- H05K2203/0207—Partly drilling through substrate until a controlled depth, e.g. with end-point detection
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Printing Elements For Providing Electric Connections Between Printed Circuits (AREA)
- Production Of Multi-Layered Print Wiring Board (AREA)
Abstract
The invention discloses a method for controlling a back drilling stub of a stepped hole of a PCB (printed circuit board), which comprises the following steps of: firstly, mechanically drilling a through hole in a PCB, wherein the diameter of the through hole is r; the sharp angle of a drill knife for drilling the through hole is as follows; step two, performing depth control drilling coaxially with the through hole, wherein the diameter of a depth control drilling cutter is R, and R is larger than R; step three, depositing copper; step four, electroplating; and fifthly, back drilling is carried out coaxially with the through hole. The invention determines the range of the back drilling depth through the limitation of all relevant conditions so as to ensure the length of the stub of the back drilling and not to damage the copper column connected with the inner layer at the depth control section.
Description
Technical Field
The invention belongs to the field of PCB (printed circuit board) manufacturing, and particularly relates to a PCB stepped hole back drilling stub control method.
Background
With the development of 5G high-speed products, PCBs move forward towards a high-density and high-integration direction, and particularly, the requirements on a high layer number, high wiring density and low stub (stub) are more and more, and one method for improving the wiring density is to perform step back drilling, depth control drilling through small holes, and back drilling diameter processing with the large diameter of the depth control drilling hole and the like; compared with the conventional back drilling hole, the back drilling hole has larger diameter than the through hole, thereby causing the waste of space.
For example, a through hole of 0.4mm is taken as an example, a drill of 0.4mm is conventionally used, and a layer of copper is plated on the hole wall through copper deposition and electroplating; to control stub, a drill bit (0.6 mm) 0.2mm larger than the through hole is generally used to back drill from the back surface to ensure that the excess copper wall of the hole is drilled. And a form of a step hole and a back drill is adopted; firstly, drilling a through hole of 0.2mm, then, controlling depth drilling by a drill bit of 0.4mm, drilling through a target conduction layer, and then, copper deposition and electroplating; carrying out back drilling after electroplating, wherein a drill bit (0.4 mm) which is 0.2mm larger than the small hole is only needed; this allows the back-drilled hole diameter to be reduced significantly, routing closer to the hole.
When the step-hole cloth is processed, the precision of the drilling is influenced, the alignment degree of the internal drilling machine is calculated according to six sigma (+/-3 sigma), and the precision of the hole position is +/-0.075 mm. Therefore, the depth control hole and the back drilling hole are 0.075-0.125mm larger than the single side of the through hole. Although the diameter of the back drilling tool is larger than that of the through hole, the copper in the small hole can be completely removed, when the back drilling tool is larger than the deep hole, the following defects exist, when the back drilling tool deviates relative to the deep hole, according to the conventional back drilling stub control, a customer requires that the stub is less than 0.254mm in length, and the common board edge test coupon controls the stub to be about 0.127mm in median value; according to conventional control, when the plate edge back drill and the depth control drill do not deviate, and a certain part of a pattern deviates, reliability risks such as open circuit of a welding ring and the like may occur.
To circumvent this risk of step back drilling, more precise depth control is required. The conventional back drilling cutter can cover the influence of hole position deviation of a drilling hole, the influenced factors mainly include plate thickness range, and the risk of not opening a circuit can be ensured when the stub is confirmed to be larger than the plate thickness range in a test coupoun slice; however, for step back drilling, in addition to the extreme difference in plate thickness, there is also the risk of hole deviation causing local open circuits.
A stub control method for back drilling of a stepped hole is realized by the flow of mechanical drilling of a through hole, depth control drilling, copper deposition, electroplating and back drilling. The same set of positioning hole can be selected by mechanically drilling the through hole and the deep hole, the deep hole is continuously controlled after the through hole is drilled, the tool diameter of the general deep hole control drill is increased by 0.075-0.1 mm larger than the through hole, and the deep hole control drill and the through hole are guaranteed to be aligned. During back drilling, the back drill is 0.075-0.125mm larger than the single side of the through hole and is influenced by the drilling precision of the back drill, the back drill can completely cover the through hole, but the back drill and the deep control hole have alignment deviation; when the back drill is used for drilling from the back of the deep control hole, dislocation can occur, the conventional stub first plate is confirmed to cause the risk of drilling a local hole wall, and the residual end of the hole wall on the other side is too long.
Disclosure of Invention
The invention aims to provide a method for controlling the back drilling stub of a stepped hole of a PCB (printed circuit board). The invention determines the range of the back drilling depth by limiting all relevant conditions so as to ensure the length of a stub of the back drilling and not to damage a copper column at a depth control section.
In order to solve the problems, the technical scheme of the invention is as follows:
a method for controlling a PCB stepped hole back drilling stub comprises the following steps:
firstly, mechanically drilling a through hole in a PCB, wherein the diameter of the through hole is r; the sharp angle of the drill knife for drilling the through hole is ϴ;
step two, performing depth control drilling coaxially with the through hole, wherein the diameter of a depth control drilling cutter is R, and R is larger than R;
step three, copper deposition;
step four, electroplating;
fifthly, back drilling is carried out coaxially with the through hole; the diameter of a drill bit of the back drill is R, the distance from a target layer of the back drill to the plate surface is H1+ sutb, the depth of the back drill is H, and the distance from the target layer of the depth drill to the plate surface is L = H-H1-sutb; h represents the thickness of the PCB; the depth of the depth control drill is h2;
wherein, when the depth control drilling is carried out, the depth of the depth control drilling is h2> L + R/2 × cot (ϴ/2) + the maximum stub value + b, and b represents a safe distance;
under the condition of non-deviation of alignment, the back drilling depth h>h1+r/2*cot(ϴ/2)+ σ 2 H1/H + c, c represents the back-drilling safety distance; sigma 2 The plate thickness range is shown;
the length of b + stub is required to be not less than sigma 2 L/H + c; σ represents the back drill deviation distance;
the length of the stub is more than or equal to sigma 2 × L/H + c + b, and the length of the stub is in a preset requirement range;
control 0.025-sigma 2 *L/H≤b≤0.15-σ 2 *L/H；
Limiting the back drilling depth h when the back drilling deviates sigma relative to the depth control drilling>h1+（r/2-σ）*cot(ϴ/2)+ σ 2 *h1/H+c。
In a further improvement, the preset required range of the length of the stub is 0.05 mm-0.25 mm.
In a further improvement, b is between 0.05mm and 0.25 mm.
The invention has the advantages that:
the invention determines the range of the back drilling depth through the limitation of all relevant conditions so as to ensure the stub length of the back drilling and not to damage the copper column at the depth control section.
Description of the drawings:
FIG. 1 is a schematic view of a back drill without deviation;
fig. 2 is a schematic diagram of back drill offset.
The specific implementation mode is as follows:
the drilling process of the invention is as follows:
as shown in the figures 1 and 2, the thickness of the plate H, the diameter of a back-drilling and depth-control drilling cutter is R, the diameter of a small hole is R, the sharp angle of the drilling cutter is ϴ, the target layer to plate surface of the back-drilling is H1+ stub, and the depth of the back-drilling is H;the depth control drill target layer to the plate surface is L = H-H1-stub, the depth control drill depth is H2, and the stub is required to be 0.05 mm-0.25 mm. The deviation distance of the back drilling tool is sigma; the plate thickness has a range of σ 2 。
Main control requirement (1): the depth control depth is h2> L + R/2 & gtcot (ϴ/2) + maximum stub value + b (safety distance);
(2): under the condition of non-deviation of alignment, the back drilling depth h>h1+r/2*cot(ϴ/2)+ σ 2 H1/H + c (backdrilling safety distance);
(3) the method comprises the following steps: b + stub is not less than sigma 2 *L/H+c
(4) The c value is generally 0.025-0.1 mm; stub is greater than or equal to sigma 2 L/H + c + b is between 0.05mm and 0.25mm,
so that b is between 0.025-sigma 2 *L/H ~ 0.15-σ 2 *L/H。
(5) When the backdrill is offset sigma relative to the backdrill, the backdrill depth H > H1+ (r/2-sigma) × ot (ϴ/2) + sigma 2 × H1/H + c (backdrill safe distance).
The back drilling can be protected from damaging the hole copper of the depth control section and the bonding pad of the target layer through the steps.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (3)
1. A method for controlling a back drilling stub of a stepped hole of a PCB (printed circuit board) is characterized by comprising the following steps of:
firstly, mechanically drilling a through hole in a PCB, wherein the diameter of the through hole is r; the sharp angle of the drill knife for drilling the through hole is ϴ;
step two, performing depth control drilling coaxially with the through hole, wherein the diameter of a depth control drilling cutter is R, and R is larger than R;
step three, copper deposition;
step four, electroplating;
fifthly, back drilling is carried out coaxially with the through hole; the diameter of a drill bit of the back drill is R, the distance from a back drill target layer to a plate surface is H1+ stub, the depth of the back drill is H, and the distance from a depth control drill target layer to the plate surface is L = H-H1-stub; h represents the thickness of the PCB; the depth of the depth control drill is h2;
wherein, when the depth control drilling is carried out, the depth of the depth control drilling is h2> L + R/2 × cot (ϴ/2) + the maximum stub value + b, and b represents a safe distance;
under the condition of non-deviation of alignment, the back drilling depth h>h1+r/2*cot(ϴ/2)+ σ 2 H1/H + c, c represents the back-drilling safety distance; sigma 2 Showing the plate thickness range;
the length of b + stub is required to be not less than sigma 2 *L/H+c；
Control 0.025-sigma 2 *L/H≤b≤0.15-σ 2 *L/H；
Limiting the back drilling depth h when the back drilling is deviated from the depth control drilling>h1+（r/2-σ）*cot(ϴ/2)+σ 2 *h1/H+c。
2. The method for controlling the stepped hole back-drilling stub of the PCB of claim 1, wherein the preset required range of the length of the stub is 0.05 mm-0.25 mm.
3. The method for controlling the stepped hole back drilling stub of the PCB of claim 1, wherein b is between 0.025mm and 0.25 mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011173903.1A CN112165781B (en) | 2020-10-28 | 2020-10-28 | Method for controlling back drilling stub of stepped hole of PCB |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011173903.1A CN112165781B (en) | 2020-10-28 | 2020-10-28 | Method for controlling back drilling stub of stepped hole of PCB |
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| Publication Number | Publication Date |
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| CN112165781A CN112165781A (en) | 2021-01-01 |
| CN112165781B true CN112165781B (en) | 2022-09-13 |
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| CN202011173903.1A Active CN112165781B (en) | 2020-10-28 | 2020-10-28 | Method for controlling back drilling stub of stepped hole of PCB |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113111292B (en) * | 2021-03-01 | 2023-05-26 | 广州广合科技股份有限公司 | Method for automatically calculating back drilling depth, electronic equipment and storage medium |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012222187A (en) * | 2011-04-11 | 2012-11-12 | Nec Corp | Manufacturing method of printed circuit board and printed circuit board |
| CN104354189A (en) * | 2014-08-21 | 2015-02-18 | 深圳市大族激光科技股份有限公司 | Method for improving accuracy of back drilling holes of PCB |
| CN106134301A (en) * | 2014-01-22 | 2016-11-16 | 桑米纳公司 | Form high aspect ratio plated through holes and the method for high accuracy stub removal in the printed circuit boards |
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2020
- 2020-10-28 CN CN202011173903.1A patent/CN112165781B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012222187A (en) * | 2011-04-11 | 2012-11-12 | Nec Corp | Manufacturing method of printed circuit board and printed circuit board |
| CN106134301A (en) * | 2014-01-22 | 2016-11-16 | 桑米纳公司 | Form high aspect ratio plated through holes and the method for high accuracy stub removal in the printed circuit boards |
| CN104354189A (en) * | 2014-08-21 | 2015-02-18 | 深圳市大族激光科技股份有限公司 | Method for improving accuracy of back drilling holes of PCB |
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| CN112165781A (en) | 2021-01-01 |
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