CN108511360B

CN108511360B - Test structure and method for PCB back drilling alignment

Info

Publication number: CN108511360B
Application number: CN201810315611.3A
Authority: CN
Inventors: 万里鹏; 刘梦茹; 纪成光
Original assignee: Shengyi Electronics Co Ltd
Current assignee: Shengyi Electronics Co Ltd
Priority date: 2018-04-10
Filing date: 2018-04-10
Publication date: 2021-05-25
Anticipated expiration: 2038-04-10
Also published as: CN108511360A

Abstract

The invention discloses a test structure and a test method for PCB back drilling alignment degree, and relates to the PCB manufacturing technology. The method comprises the following steps: arranging a test structure on the PCB; drilling a borehole and a reference hole in the test structure; back drilling the drill hole to obtain a back drill hole; and determining the alignment degree of the back drilling through the position relation of the back drilling hole and the reference hole. Before back drilling on the circuit pattern, the back drilling on the test structure is taken as a reference, and whether the back drilling deviates holes is judged according to the position relation between the back drilling holes and a plurality of reference holes, so that whether normal production can be carried out is determined. On one hand, whether the hole deviates or not can be directly judged from the surface of the module without enlarging and observing the hole wall; and on the other hand, back drilling is carried out on the module in advance and the back drilling is checked, so that waste caused by unqualified back drilling on the circuit pattern can be avoided.

Description

Test structure and method for PCB back drilling alignment

Technical Field

The invention relates to a PCB manufacturing technology, in particular to a PCB back drilling alignment test structure and a method.

Background

In the manufacturing of the PCB, the back drilling is used for drilling a through hole section which does not have any connection or transmission function, so that the phenomena of reflection, scattering, delay and the like of high-speed signal transmission are avoided, and the signal is prevented from being distorted. In the back drilling manufacturing process, if back drilling and one drilling of an existing deviated hole are carried out, copper on the hole wall of the back drilling part can not be completely drilled, and therefore signal transmission distortion is caused.

In the prior art, in order to judge whether back drilling is deviated or not, the fact that whether back drilling is deviated or not in a board is observed by naked eyes through a ten-fold mirror directly after back drilling is generally adopted. However, this method has a drawback that observation is easy when the back drill hole is shallow, and observation is difficult with the naked eye when the back drill depth is deep, and erroneous judgment is likely to be caused by unclear observation or a long time is required.

Disclosure of Invention

The invention aims to provide a test structure and a method for alignment of a PCB back drill, which can judge whether the alignment of the back drill meets the production requirement or not through the test structure.

In order to achieve the purpose, the invention adopts the following technical scheme:

in one aspect, the present invention provides a test structure for PCB backdrill alignment, including: a plurality of test units each comprising a bore and a plurality of reference holes;

in the test unit, a plurality of reference holes are arranged around the drill hole, and the distance between the center of the drill hole and the center of each reference hole is equal;

the method comprises the following steps that a back drilling hole is obtained by the back drilling of the drill hole, and when the circle center of the back drilling hole is coincident with the circle center of the drill hole, the minimum distance from the hole wall of the back drilling hole to the hole wall of the reference hole is a set hole spacing;

the plurality of test units correspond to values of the hole intervals.

The test structure is arranged on the periphery of the circuit pattern unit of the PCB.

Wherein the pitch of the holes is 1mil to 10 mils; between the test unit of multiunit, the difference of hole interval is 0.1mil to 1 mil.

Further, two adjacent test units have the reference hole in common.

In another aspect, the present invention provides a method for testing alignment of PCB backdrilling, comprising:

arranging the test structure on a PCB;

drilling a borehole and a reference hole in the test structure;

back drilling the drill hole to obtain a back drill hole;

and determining the alignment degree of the back drilling through the position relation of the back drilling hole and the reference hole.

Wherein determining backdrilling alignment through the positional relationship of the backdrilled hole and the reference hole comprises:

a determination is made for each test cell on a test structure,

and if the back drilling hole is separated from each reference hole in the test unit, the minimum value of the hole spacing between the back drilling hole and the reference hole in the test unit corresponding to the test structure is the back drilling alignment degree.

Wherein, set up above-mentioned test structure on PCB, include:

respectively arranging a test structure around the circuit pattern unit on the PCB as a group of test structures;

and respectively arranging at least one group of test structures for back drilling holes with different diameters on the PCB.

Further, after determining the alignment degree of the back drilling by the positional relationship between the back drilling hole and the reference hole, the method further includes:

and determining whether to carry out production according to the back drilling alignment degree.

Specifically, determining whether to perform production according to the back drill alignment degree comprises:

if the alignment degree of the back drill is larger than the preset required alignment degree, determining that the alignment degree of the back drill is insufficient, not producing, adjusting the drilling parameters of the back drill, and carrying out the alignment degree test of the back drill again;

if the back drilling alignment is less than or equal to the preset required alignment, the production can be carried out.

The invention has the beneficial effects that:

before back drilling on the circuit pattern, the back drilling on the test structure is taken as a reference, and whether the alignment degree of the back drilling meets the production requirement or not is judged according to the position relation between the back drilling hole and a plurality of reference holes. On one hand, whether the hole deviates or not can be directly judged from the surface of the module without enlarging and observing the hole wall; and on the other hand, back drilling is carried out on the module in advance and the back drilling is checked, so that waste caused by unqualified back drilling on the circuit pattern can be avoided.

Drawings

FIG. 1 is a schematic diagram of a PCB backdrill alignment test structure according to an embodiment of the present invention;

FIG. 2 is a flowchart of a PCB backdrill alignment testing method according to a second embodiment of the present invention;

FIG. 3 is a schematic diagram of determining alignment of backdrilling in a second embodiment of the present invention;

fig. 4 is a schematic diagram of a position of a test structure on a PCB according to a second embodiment of the present invention.

In the figure: 1. drilling a hole; 2. a reference hole; 3. back drilling; 4. a line pattern unit; 5. testing the structure; 6. and a test unit.

Detailed Description

In order to make the technical problems solved, technical solutions adopted and technical effects achieved by the present invention clearer, the technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments.

Example one

This embodiment provides a test structure of PCB back drilling alignment degree, is applicable to the PCB that needs the back drilling, can judge whether the back drilling that will go on PCB is inclined to one side the hole, is convenient for decide whether to carry out production on next step, perhaps adjusts the back drilling position.

Fig. 1 is a schematic diagram of a test structure for PCB backdrill alignment provided in this embodiment. As shown in fig. 1, the test structure 5 includes: a plurality of test units 6, the test units 6 consisting of a borehole 1 and a plurality of reference holes 2, the borehole 1 being backdrilled to obtain a backdrilled hole 3.

In one test unit 6, a plurality of reference holes 2 are arranged around the drill hole 1, and can be arranged in different directions around the drill hole 1, the distance between the center of the drill hole 1 and each reference hole 2 is equal, and when the center of the back drill hole 3 coincides with the center of the drill hole 1, the minimum distance from the hole wall of the back drill hole 3 to the hole wall of the reference hole 2 is a set hole spacing S. In order to ensure the accuracy of the determination, it is preferable that each of the drill holes 1 corresponds to at least four reference holes 2, and the reference holes 2 are not limited in radius and are generally drilled simultaneously with one of the drill holes 1 at a radius equal to that of one of the drill holes 1.

The plurality of test units 6 correspond to a plurality of values of the hole spacing S, such as S1, S2, S3 … … Sn, and the like in fig. 1. The hole spacing S takes the value of 1mil to 10 mils; among the multiple groups of test units 6, the difference of the hole spacing S is 0.1-1 mil, and the difference of the hole spacing S in general production is 1 mil.

The test structure is arranged around the circuit pattern unit of the PCB. The plurality of test units 6 can be arranged and arranged arbitrarily, and the reference holes 2 can be shared among the test units 6 in order to reduce the occupied area of the test structure.

The test structure provided by the embodiment can be designed according to the requirement of alignment of the back drilling hole in production, if the back drilling hole is intersected or circumscribed with the reference hole, the alignment of the back drilling hole is insufficient, and production is not required; if the back drilling hole is away from the reference hole, the minimum value of the hole spacing between the back drilling hole and the reference hole in the corresponding test unit is the alignment degree of the back drilling; further, if the back drill alignment meets the production requirements, actual production can be performed on the circuit pattern. The result can be directly observed from the surface of the PCB, the inside of the hole wall is not required to be observed in an enlarged mode, and the time is saved.

Example two

In this embodiment, the test structure provided by the above embodiment is used, and before back drilling is performed on the circuit pattern, the alignment of the back drilling is checked by performing back drilling on the test structure.

Fig. 2 is a flowchart of a method for testing PCB backdrilling alignment according to a second embodiment of the present invention. As shown in fig. 2, the test method includes the steps of:

and S11, arranging a test structure on the PCB.

Fig. 4 is a schematic diagram of a position of a test structure on a PCB according to a second embodiment of the present invention. As explained with reference to fig. 4, one test structure 5 is disposed around the circuit pattern unit 4, respectively, as a group of test structures. In a preferred embodiment, one test structure 5 is disposed at each of the four corners of the line pattern unit 4.

And respectively arranging at least one group of test structures for back drilling holes with different diameters on the circuit graphic unit of the PCB.

And S12, drilling a drilling hole and a reference hole on the test structure.

A drill hole and reference hole in the test structure need to be drilled together with a drill hole in the circuit pattern unit on the PCB using the same drilling parameters.

And S13, back drilling the drill hole to obtain a back drill hole.

Setting back drilling parameters according to production requirements, and drilling a back drilling hole on the back of a drilling hole. The back drilling depth is not limited.

And S14, determining the alignment degree of the back drilling according to the position relation of the back drilling hole and the reference hole.

And judging each test unit on one test structure, and if the back drilling hole is separated from each reference hole in the test unit, the minimum value of the hole spacing between the back drilling hole and the reference hole in the test unit meeting the condition on the test structure is the back drilling alignment.

FIG. 3 is a schematic diagram of determining backdrill alignment in the present embodiment. As shown in fig. 3, the test structure 5 is disposed on the PCB, and on each test unit 6 of the test structure 5, a back drill corresponding to one drill hole 1 is used to obtain a back drill hole 3, when the hole spacing is S1, the back drill hole 3 intersects with the reference hole 2, when the hole spacing is S2, the back drill hole 3 is tangent to the reference hole 2, and the back drills are all offset holes; when the hole pitch is S3, S4, the back drill hole 3 is separated from the reference hole 2, and the back drill alignment degree takes the minimum value of S3, S4, i.e., S3.

Further, step S14 is followed by:

and S15, determining whether to carry out production according to the back drilling alignment degree.

If the back drilling deviation hole or the back drilling alignment degree is larger than the preset required alignment degree, determining that the back drilling alignment degree is insufficient, not performing production, adjusting the drilling parameters of the back drilling, and performing the back drilling alignment degree test again; if the back drilling alignment is less than the preset required alignment, the production can be carried out.

For example, if the alignment degree of the back drill is 5mil and the preset required alignment degree is 6mil, the alignment degree of the back drill meets the production requirement, and the production can be performed; the alignment of the back drill is 5mil, and the alignment of the preset requirement is 4mil, which indicates that the alignment capability of the back drill is insufficient and needs to be adjusted.

The test method provided by the embodiment can realize the judgment of the alignment degree through mechanical measurement or image recognition. Even human observation can easily see whether the holes are deviated from the surface of the module. The testing method can know whether the back drill meets the precision requirement of production or not before actual production, and conveniently determines whether to carry out next production or not or correspondingly adjusts the drilling parameters of the back drill.

The technical principle of the present invention is described above in connection with specific embodiments. The description is made for the purpose of illustrating the principles of the invention and should not be construed in any way as limiting the scope of the invention. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without inventive effort, which would fall within the scope of the present invention.

Claims

1. A PCB back drilling alignment test structure, comprising: a plurality of test units each comprising a bore and a plurality of reference holes;

the plurality of test units correspond to the values of the hole intervals, and two adjacent test units have the common reference hole.

2. The test structure of claim 1, wherein:

the test structure is arranged around the circuit pattern unit of the PCB.

3. The test structure of claim 1, wherein:

the distance between the holes is 1mil to 10 mils;

between the test unit of multiunit, the difference of hole interval is 0.1mil to 1 mil.

4. A method for testing PCB back drilling alignment degree is characterized in that:

providing the test structure of any one of claims 1 to 3 on a PCB;

5. The testing method of claim 4, wherein determining backdrilling alignment from the positional relationship of the backdrilled hole to the reference hole comprises:

and judging each test unit on one test structure, and if the back drilling hole is separated from each reference hole in the test unit, taking the minimum value of the hole spacing between the back drilling hole and the reference hole in the corresponding test unit on the test structure as the back drilling alignment degree.

6. The method of claim 4 or 5, wherein providing the test structure on the PCB comprises:

7. The testing method of claim 5, after determining backdrilling alignment by the positional relationship of the backdrilled hole and the reference hole, further comprising:

8. The method of testing of claim 7, wherein determining whether to produce based on the backdrill alignment comprises:

if the alignment degree of the back drill is greater than the preset required alignment degree, the alignment degree of the back drill is insufficient, production is not carried out, and drilling parameters of the back drill are adjusted;