阅读说明：本技术 一种多层印刷线路板相邻层之间对位的检测方法 (Method for detecting alignment between adjacent layers of multilayer printed circuit board ) 是由 张伟连 于 2019-08-30 设计创作，主要内容包括：本发明公开了一种多层印刷线路板相邻层之间对位的检测方法,包括以下步骤：每个内层板设有x向检测模块,x向检测模块上设有第一Pad,每个第一Pad设有第一内层导线；将内层板压合成多层印刷线路板；多层印刷线路板上设有左通孔和右通孔,第一Pad对应设在左通孔与右通孔之间,沿从后到前的方向,第一Pad与左通孔的间距逐渐变大,第一Pad与右通孔的间距逐渐变小,第一内层导线连至外层板；零偏移状态下,第一Pad与对应的左通孔、右通孔均不导通,使用电阻仪测量每层内层板的第一Pad与左通孔或右通孔,确认第一Pad的偏移方向,并记录对应第一Pad导通的最大间距；计算出每层内层板的对位数据△x。本发明相对于微切片方法,具有效率高、不破坏线路板的特点。(The invention discloses a method for detecting the alignment between adjacent layers of a multilayer printed circuit board, which comprises the following steps: each inner layer board is provided with an x-direction detection module, the x-direction detection module is provided with a first Pad, and each first Pad is provided with a first inner layer lead; laminating the inner layer board to form a multilayer printed circuit board; the multilayer printed circuit board is provided with a left through hole and a right through hole, the first Pad is correspondingly arranged between the left through hole and the right through hole, the distance between the first Pad and the left through hole is gradually increased along the direction from back to front, the distance between the first Pad and the right through hole is gradually decreased, and the first inner layer lead is connected to the outer layer board; in a zero offset state, the first Pad is not conducted with the corresponding left through hole and the right through hole, a resistance meter is used for measuring the first Pad of the interlayer plate in each layer and the left through hole or the right through hole, the offset direction of the first Pad is confirmed, and the maximum distance corresponding to the conduction of the first Pad is recorded; and calculating the alignment data delta x of the laminates in each layer. Compared with a micro-slicing method, the method has the characteristics of high efficiency and no damage to a circuit board.)

1. A method for detecting the alignment between adjacent layers of a multilayer printed circuit board is characterized by comprising the following steps:

Step A: an x-direction detection module (210) is arranged at the same position of each inner layer board (100) forming the multilayer printed circuit board; each x-direction detection module (210) is provided with a plurality of first pads (213), the first pads (213) are arranged in a single row along the front-back direction and gradually move to the right in a step shape, and each first Pad (213) is provided with a first inner layer lead (214);

And B: pressing a plurality of inner layer boards (100), and respectively pressing a first outer layer board and a second outer layer board (500) on the end surfaces of the upper end and the lower end to form a multilayer printed circuit board;

and C: a plurality of left through holes (211) and right through holes (212) are formed in the multilayer printed circuit board, the left through holes (211) correspond to the right through holes (212) one by one, the left through holes (211) are vertically arranged in a row along the front-back direction, each left through hole (211) in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer plate (500), the right through holes (212) are vertically arranged in a row along the front-back direction, and each right through hole (212) in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer plate (500); the number of the first pads (213) of the x-direction detection module (210) corresponds to that of the left through holes (211) one by one, the first pads (213) are arranged between the left through holes (211) and the right through holes (212), and along the direction from back to front, the distance between the first pads (213) and the left through holes (211) is increasingly larger, and the distance between the first pads (213) and the right through holes (212) is increasingly smaller; a plurality of columns of third through holes (215) are arranged on the second outer layer plate (500), one column of the third through holes (215) corresponds to one inner layer plate (100), and the numbers are marked to identify the number of layers of the corresponding inner layer plate (100); the first inner layer lead (214) of each inner layer board (100) is connected to the second outer layer board (500) through the corresponding third row of through holes (215);

Step D: in a zero offset state, the first Pad (213) is not conducted with the corresponding left through hole (211) and right through hole (212), a resistance meter is used for measuring the first Pad (213) of each interlayer plate (100) and the corresponding left through hole (211) or right through hole (212), along the direction from back to front, the nth left through hole (211) which can be conducted at the foremost end is marked as '-n', the right through hole (212) which can be conducted at the rearmost end is marked as '+ n', and the offset distance of the adjacent two first pads (213) multiplied by n is the alignment data delta x of each interlayer plate (100) in the left-right direction.

2. The method for detecting the alignment between adjacent layers of a multilayer printed wiring board according to claim 1, wherein in the step a: the detection device is characterized by further comprising y-direction detection modules (230) which are perpendicular to the x-direction detection modules (210), wherein each y-direction detection module (210) is provided with a plurality of second pads (233), the second pads (233) are arranged in a single row along the left-right direction and gradually lean backwards in a stepped manner, and each second Pad (233) is provided with a second inner layer lead (234); in the step C: a plurality of front through holes (231) and rear through holes (232) are formed in the multilayer printed circuit board, the front through holes (231) correspond to the rear through holes (232) one by one, the front through holes (231) are horizontally arranged in a row along the left-right direction, each front through hole (231) in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer plate (500), the rear through holes (232) are horizontally arranged in a row along the left-right direction, and each rear through hole (232) in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer plate (500); the number of the second pads (233) of the y-direction detection module (230) corresponds to the number of the front through holes (231) one by one, the second pads (233) are arranged between the front through holes (231) and the rear through holes (232), and along the left-to-right direction, the distance between the second pads (233) and the front through holes (231) is gradually increased, the distance between the second pads (233) and the rear through holes (232) is gradually decreased, a plurality of rows of fourth rows of through holes (235) are arranged on the second outer layer plate (500), one row of the fourth rows of through holes (235) corresponds to one inner layer plate (100), and the numbers are marked to identify the number of layers of the corresponding inner layer plate (100); the second inner layer conductor (234) of each inner layer board (100) is connected to the second outer layer board (500) through a fourth column of through holes (235).

3. the method for detecting the alignment between adjacent layers of a multilayer printed wiring board according to claim 2, wherein the step D further comprises the steps of:

Step F: measuring the alignment data Deltay of the adjacent inner-layer boards (100) in the front-back direction according to the step of measuring the alignment data Deltax of the adjacent inner-layer boards (100) in the left-right direction;

step F: and calculating the alignment data of the adjacent inner plates (100) in the radial direction by using SQRT (delta x ^2 plus delta y ^ 2).

4. The method for detecting the alignment between adjacent layers of a multilayer printed wiring board according to claim 2, wherein in the step C: the front through hole (231) is a minus direction test point, and the rear through hole (232) is a plus direction test point.

5. The method for detecting the alignment between adjacent layers of a multilayer printed wiring board according to claim 2, wherein in the step a: the y-direction detection modules (230) are arranged in two groups, and the two groups of y-direction detection modules (230) are respectively arranged at the diagonal positions of each inner layer board (100).

6. the method for detecting the alignment between adjacent layers of a multilayer printed wiring board according to claim 2, wherein in the step a: the x-direction detection module (210), the y-direction detection module (230) and the inner plate (100) are integrally processed and formed.

7. The method for detecting the alignment between adjacent layers of a multilayer printed wiring board according to claim 1, wherein in the step a: the x-direction detection modules (210) are arranged in two groups, and the two groups of x-direction detection modules (210) are respectively arranged at the diagonal positions of each inner-layer plate (100).

8. The method for detecting the alignment between adjacent layers of a multilayer printed wiring board according to claim 1, wherein in the step C: the left through hole (211) is a minus direction test point, and the right through hole (212) is a plus direction test point.

Technical Field

The invention relates to the technical field of circuit board manufacturing, in particular to a method for detecting alignment between adjacent layers of a multilayer printed circuit board.

Background

with the continuous progress of the internet, electronic information and signals are developing towards large capacity, diversification and rapidness. The signal amount per wavelength is increased from 10Gbps to 40Gbps, and even the signal capacity of Tbps can be achieved due to the increase of the multiplexing. The multilayer printed circuit board is designed and applied more and more widely, and has strict requirements on the reliability and quality of products, especially the requirements on the stability and integrity of signal transmission. Alignment between adjacent layers is one of factors affecting signal transmission, and some high-end printed wiring boards have strict alignment requirements between adjacent layers. At present, a microtome measurement method is usually adopted for measuring the alignment between adjacent layers, but the method is long in time consumption, has local destructiveness on a printed circuit board, and is not suitable for batch alignment detection.

Disclosure of Invention

the present invention is directed to solving, at least to some extent, one of the above-mentioned problems in the related art. Therefore, the invention provides a method for detecting the alignment between adjacent layers of the multilayer printed circuit board, which can simplify the alignment detection process and improve the detection efficiency.

the invention provides a method for detecting the alignment between adjacent layers of a multilayer printed circuit board, which comprises the following steps:

Step A: an x-direction detection module is arranged at the same position of each inner layer board forming the multilayer printed circuit board; each x-direction detection module is provided with a plurality of first pads, the first pads are arranged in a single row along the front-back direction and gradually approach to the right in a step shape, and each first Pad is provided with a first inner-layer lead;

And B: pressing a plurality of inner layer boards, and respectively pressing a first outer layer board and a second outer layer board on the end faces of the upper end and the lower end to form a multilayer printed circuit board;

And C: a plurality of left through holes and right through holes are formed in the multilayer printed circuit board, the left through holes correspond to the right through holes one by one, the left through holes are vertically arranged in a row along the front-back direction, each left through hole in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer board, the right through holes are vertically arranged in a row along the front-back direction, and each right through hole in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer board; the number of the first pads of the x-direction detection module corresponds to that of the left through holes one to one, the first pads are arranged between the left through holes and the right through holes, the distance between the first pads and the left through holes is increasingly larger along the direction from back to front, and the distance between the first pads and the right through holes is increasingly smaller; a plurality of columns of third through holes are arranged on the second outer layer plate, one column of the third through holes corresponds to one inner layer plate, and the third through holes are labeled to identify the number of layers of the corresponding inner layer plate; the first inner layer lead of each inner layer plate is connected to the second outer layer plate through the corresponding third row of through holes;

Step D: in a zero offset state, the first Pad is not conducted with the corresponding left through hole and the right through hole, a resistance meter is used for measuring the first Pad of the interlayer plate in each layer and the corresponding left through hole or right through hole, the nth left through hole which can be conducted at the foremost end is marked as '-n' along the direction from back to front, the right through hole which can be conducted at the rearmost end is marked as '+ n', and the offset distance of n multiplied by two adjacent first pads is the alignment data Deltax of the interlayer plate in each layer in the left-right direction.

the method for detecting the alignment between the adjacent layers of the multilayer printed circuit board at least has the following beneficial effects: through being provided with x on the same position at each inner plate to detection module, x is provided with the first Pad with left through-hole and right through-hole one-to-one to detection module, along the direction from back to front, the interval grow gradually of first Pad and left through-hole, just the interval of first Pad and right through-hole diminishes gradually, each first Pad is provided with first inlayer wire respectively and draws forth, just first inlayer wire is connected to through the third row through-hole that corresponds the second outer plate, and the third row through-hole that is in the corresponding of the inlayer of different layers sets up the different positions on the outer plate to carry out corresponding reference numeral. During detection, a resistance meter is used for measuring the conduction condition of the first Pad of the corresponding inner layer plate and the corresponding left through hole and right through hole, firstly, the conduction of the first Pad and the left through hole or the right through hole is confirmed, the offset direction ("+" or "-") of the first Pad is confirmed, and the maximum distance between the first Pad of the corresponding inner layer plate and the corresponding left through hole or right through hole in the conduction state is respectively recorded; and subtracting the measured values of the adjacent inner-layer plates to obtain the contraposition data delta x of the adjacent inner-layer plates in the left and right directions, judging whether the delta x falls in the required detection range, and further judging whether the product is qualified. The invention has scientific and reasonable arrangement, and can measure the alignment data of adjacent layers by arranging the x-direction detection module on each inner layer plate and using a resistance meter measuring method. Compared with a micro-slicing method, the method has the characteristics of high efficiency, suitability for batch detection and no damage to the multilayer printed circuit board.

According to the method for detecting the alignment between the adjacent layers of the multilayer printed circuit board, the step A comprises the following steps: the device also comprises y-direction detection modules which are perpendicular to the x-direction detection modules, each y-direction detection module is provided with a plurality of second pads, the second pads are arranged in a single row along the left-right direction and gradually lean backwards in a step shape, and each second Pad is provided with a second inner layer lead; in the step C: a plurality of front through holes and rear through holes are formed in the multilayer printed circuit board, the front through holes correspond to the rear through holes one by one, the front through holes are horizontally arranged in a row along the left-right direction, each front through hole in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer plate, the rear through holes are horizontally arranged in a row along the left-right direction, and each rear through hole in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer plate; the number of the second pads of the y-direction detection module corresponds to the number of the front through holes one by one, the second pads are arranged between the front through holes and the rear through holes, the distance between the second pads and the front through holes is larger and larger along the left-to-right direction, the distance between the second pads and the rear through holes is smaller and smaller, a plurality of rows of fourth rows of through holes are arranged on the second outer layer plate, one row of the fourth rows of through holes corresponds to one inner layer plate, and the inner layer plates are numbered to identify the number of layers of the corresponding inner layer plate; the second inner layer lead of each inner layer board is connected to the second outer layer board through the corresponding fourth row of through holes.

according to the method for detecting the alignment between the adjacent layers of the multilayer printed circuit board, the step D further comprises the following steps:

Step E: measuring the alignment data Deltay of the adjacent inner-layer plates in the front and back directions according to the step of measuring the alignment data Deltax of the adjacent inner-layer plates in the left and right directions;

step F: and calculating the alignment data of the adjacent inner plates in the radial direction by using SQRT (delta x ^2 plus delta y ^ 2).

According to the method for detecting the alignment between the adjacent layers of the multilayer printed circuit board, in the step C: the front through hole is a minus direction test point, and the rear through hole is a plus direction test point.

According to the detection method for the alignment between the adjacent layers of the multilayer printed circuit board, two groups of y-direction detection modules are arranged, and the two groups of y-direction detection modules are respectively arranged at the diagonal positions of each inner layer board.

according to the method for detecting the alignment between the adjacent layers of the multilayer printed circuit board, the step A comprises the following steps: the x-direction detection module, the y-direction detection module and the inner layer plate are integrally processed and formed.

according to the method for detecting the alignment between the adjacent layers of the multilayer printed circuit board, the step A comprises the following steps: the x-direction detection modules are arranged in two groups, and the two groups of x-direction detection modules are respectively arranged at the diagonal positions of each inner-layer plate.

According to the method for detecting the alignment between the adjacent layers of the multilayer printed circuit board, in the step C: the left row of through holes are used as the < - > direction test points, and the right row of through holes are used as the < + > direction test points.

Drawings

the invention is further illustrated with reference to the following figures and examples.

FIG. 1 is a schematic front view of a second outer layer of an embodiment of the present invention;

FIG. 2 is an enlarged view taken at A in FIG. 1;

FIG. 3 is a schematic front view of each inner panel according to the embodiment of the present invention;

FIG. 4 is a schematic structural diagram of an x-direction detection module according to an embodiment of the present invention;

Fig. 5 is a schematic structural diagram of a y-direction detection module in the embodiment of the present invention.

Detailed Description

reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

Referring to fig. 1 to 5, a method for detecting alignment between adjacent layers of a multi-layer printed circuit board according to an embodiment of the present invention includes the following steps:

Step A: an x-direction detection module 210 is arranged at the same position of each inner plate 100 forming the multilayer printed circuit board; each x-direction detection module 210 is provided with a plurality of first pads 213, the plurality of first pads 213 are arranged in a single row along the front-back direction and gradually approach to the right in a step shape, and each first Pad213 is provided with a first inner-layer lead 214;

And B: laminating a plurality of inner layer boards 100, and laminating a first outer layer board and a second outer layer board 500 on the end faces of the upper end and the lower end respectively to form a multilayer printed circuit board;

and C: a plurality of left through holes 211 and right through holes 212 are formed in the multilayer printed circuit board, the left through holes 211 correspond to the right through holes 212 one by one, the left through holes 211 are arranged in a vertical row along the front-back direction, each left through hole 211 in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer plate 500, the right through holes 212 are arranged in a vertical row along the front-back direction, and each right through hole 212 in the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer plate 500; the number of the first pads 213 of the x-direction detection module 210 corresponds to that of the left through holes 211 one by one, the first pads 213 are disposed between the left through holes 211 and the right through holes 212, and along the direction from back to front, the distance between the first pads 213 and the left through holes 211 is increasingly larger, and the distance between the first pads 213 and the right through holes 212 is increasingly smaller; a plurality of columns of third through holes 215 are arranged on the second outer layer plate 500, the column of third through holes 215 corresponds to one inner layer plate 100, and the numbers are used for identifying the number of layers of the corresponding inner layer plate 100; the first inner layer wire 214 of each inner layer board 100 is connected to the second outer layer board 500 through the corresponding third row via 215;

step D: in a zero offset state, the first Pad213 is not in conduction with the corresponding left through hole 211 and right through hole 212, a resistance meter is used for measuring the first Pad213 of the interlayer plate 100 in each layer and the corresponding left through hole 211 or right through hole 212, along the direction from back to front, the nth left through hole 211 which can be conducted at the foremost end is marked as "-n", the right through hole 212 which can be conducted at the rearmost end is marked as "+ n", and the offset distance of n multiplied by two adjacent first pads 213 is the alignment data Δ x of the interlayer plate 100 in each layer in the left-right direction.

Compared with the prior art, in the embodiment of the invention, the x-direction detection module 210 is arranged at the same position of each inner layer board 100, the x-direction detection module 210 is provided with the first pads 213 which are in one-to-one correspondence with the left through holes 211 and the right through holes 212, the distance between the first pads 213 and the left through holes 211 is gradually increased along the direction from back to front, the distance between the first pads and the right through holes 212 is gradually decreased, each first Pad213 is respectively provided with the first inner layer lead 214 to be led out, the first inner layer lead 214 is connected to the second outer layer board 500 through the corresponding third row of through holes 215, and the third rows of through holes 215 corresponding to the inner layer boards 100 in different layers are arranged at different positions on the outer layer board 500 and are correspondingly numbered. During detection, a resistance meter is used for measuring the conduction condition of the first Pad213 of the corresponding inner-layer plate 100 and the corresponding left through hole 211 or right through hole 212, firstly, the conduction of the first Pad213 and the left through hole 211 or right through hole 212 is confirmed, the deviation direction "+" or "-" of the first Pad213 is confirmed, and the maximum distance between the first Pad213 of the corresponding inner-layer plate 100 and the corresponding left through hole 211 or right through hole 212 in the conduction state is respectively recorded; subtracting the numerical values of the adjacent inner-layer boards 100 to obtain the contraposition data delta x of the adjacent inner-layer boards 100 in the left and right directions, judging whether the delta x falls within the required detection range, and further judging whether the product is qualified. The embodiment of the invention has scientific and reasonable arrangement, and the alignment data of adjacent layers can be measured by arranging the x-direction detection module 210 on the interlayer plate 100 in each layer and using a resistance measuring method. Compared with a micro-slicing method, the method has the characteristics of high efficiency, suitability for batch detection and no damage to the multilayer printed circuit board.

Specifically, as shown in fig. 4, in step D: using a second outer layer board 500 without generating left-right deviation as a reference board, measuring the conduction condition of a first Pad213 of the inner layer board 100 of each layer and a corresponding left through hole 211 and a corresponding right through hole 212 by using a resistance meter, if the inner layer board 100 of the nth layer is left-shifted, measuring that the first Pad213 of the nth layer is conducted with the corresponding left through hole 211 and is recorded as "-", and along the direction from back to front, conducting a 3 rd left through hole 211 with the corresponding first Pad213, not conducting a 4 th left through hole 211 with the corresponding first Pad213, and setting the distance between the 3 rd left through hole 211 and the corresponding first Pad213 as x3, recording the measured alignment data value delta x of the inner layer board 100 of the nth layer relative to the reference board in the left-right direction as-x 3; if the inner layer board 100 of the nth layer is shifted to the right, the resistance meter measures that the first Pad213 of the nth layer is conducted with the corresponding right through hole 212, and is recorded as "+", along the front-to-back direction, the 4 th right through hole 212 is conducted with the corresponding first Pad213, the 5 th right through hole 212 is not conducted with the corresponding first Pad213, and the distance between the 4 th right through hole 212 and the corresponding first Pad213 is x4, and then records that the measured alignment data value Δ x of the inner layer board 100 of the nth layer relative to the reference board in the left-to-right direction is + x 4.

The alignment data of two adjacent inner boards 100 may also be measured, the alignment data of the inner board 100 of the nth layer with respect to the reference board is preset to be-x 3, if the inner board 100 of the (n + 1) th layer has a left offset with respect to the inner board 100 of the nth layer, the first Pad213 of the inner board 100 of the (n + 1) th layer is communicated with the corresponding left through hole 211 and is recorded as "-", the 5 th left through hole 211 located further forward than the 3 rd left through hole 211 is communicated with the corresponding first Pad213, the first Pad213 corresponding to the 6 th left through hole 211 is not communicated, the distance between the 5 th left through hole 211 and the corresponding first Pad213 is x5, the measured alignment data value Δ x of the inner board 100 of the (n + 1) th layer with respect to the reference board in the left-right direction is recorded as-x 5, and the alignment data Δ x of the inner boards 100 of the (n + 1) th layer and the n +1 th layer in the left-right direction is preset to be-x 5-x 3), the delta x is smaller than zero, namely the inner layer board 100 of the (n + 1) th layer is leftwards offset relative to the inner layer board 100 of the nth layer, and the offset is the absolute value of the alignment data delta x; if the inner panel 100 of the (n + 1) th layer is shifted to the right with respect to the inner panel 100 of the (n) th layer, two possibilities arise: in a first possibility, the first Pad213 of the inner layer board 100 of the (n + 1) th layer is communicated with the corresponding left through hole 211, and is recorded as "-", the 1 st left through hole 211, which is further back than the 3 rd left through hole 211, is communicated with the corresponding first Pad213, the 2 nd left through hole 211 is not communicated with the corresponding first Pad213, the distance between the 1 st left through hole 211 and the corresponding first Pad213 is x1, the measured alignment data value Δ x of the inner layer board 100 of the (n + 1) th layer relative to the reference board in the left-right direction is-x 1, the alignment data Δ x of the inner layer board 100 of the (n + 1) th layer in the left-right direction is-x 1- (-x3), and Δ x is greater than zero; in a second possibility, the first Pad213 of the inner layer board 100 of the (n + 1) th layer is communicated with the corresponding right via 212, which is recorded as "+", the 2 nd right via 212 is in conduction with the corresponding first Pad213, the 3 rd right via 212 is not in conduction with the corresponding first Pad213, the distance between the 2 nd right via 212 and the corresponding first Pad213 is x2, the measured alignment data value Δ x of the inner layer board 100 of the (n + 1) th layer in the left-right direction relative to the reference board is + x2, the alignment data Δ x of the inner layer board 100 of the (n + 1) th layer in the left-right direction relative to the reference board is + x2- (-x3), and Δ x is greater than zero, that is, the inner layer board 100 of the (n + 1) th layer is shifted to the right relative to the inner layer board 100 of the (n) th layer, and the shift amount is the absolute value of the alignment data Δ x.

In some embodiments, preferably, in step a: the detection device also comprises y-direction detection modules 230 which are perpendicular to the x-direction detection modules 210, wherein each y-direction detection module 210 is provided with a plurality of second pads 233, the plurality of second pads 233 are arranged in a single row along the left-right direction and gradually lean backwards in a stepped manner, and each second Pad233 is provided with a second inner layer lead 234; in step C: a plurality of front through holes 231 and rear through holes 232 are formed in the multilayer printed circuit board, the front through holes 231 correspond to the rear through holes 232 one by one, the front through holes 231 are arranged in a horizontal row along the left-right direction, each front through hole 231 on the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer board 500, the rear through holes 232 are arranged in a horizontal row along the left-right direction, and each rear through hole 232 on the multilayer printed circuit board is provided with an outer layer lead communicated to the second outer layer board 500; the number of the second pads 233 of the y-direction detection module 230 corresponds to the number of the front through holes 231 one by one, the second pads 233 are arranged between the front through holes 231 and the rear through holes 232, and along the left-to-right direction, the distance between the second pads 233 and the front through holes 231 is increasingly larger, the distance between the second pads 233 and the rear through holes 232 is increasingly smaller, a plurality of rows of fourth rows of through holes 235 are arranged on the second outer layer plate 500, one row of the fourth rows of through holes 235 corresponds to one inner layer plate 100, and the numbers are marked to identify the number of layers of the corresponding inner layer plate 100; the second inner layer wire 234 of each inner layer board 100 is connected to the second outer layer board 500 through the corresponding fourth column of via holes 235. Specifically, as shown in fig. 5, the alignment data Δ y in the front-rear direction of the inner layer board 100 is measured by measuring the alignment data Δ x in the left-right direction of the inner layer board 100, the alignment data Δ y in the front-rear direction of the inner layer board 100 with respect to the reference plate is sequentially measured using the second outer layer board 500, which does not generate the front-rear deviation, as the reference plate, and then the alignment data Δ y in the front-rear direction of the inner layer board 100 with respect to the reference plate is subtracted from the alignment data Δ y in the front-rear direction of the inner layer board 100 in the n +1 th layer, so as to obtain a difference value as the alignment data between the adjacent two inner layer boards 100. Specifically, as shown in fig. 5, if the alignment data of the inner layer plate 100 of the nth layer with respect to the reference plate in the front-back direction is-y 3, and the alignment data of the inner layer plate 100 of the (n + 1) th layer with respect to the reference plate in the front-back direction is-y 4, the alignment data of the inner layer plate 100 of the (n + 1) th layer with respect to the inner layer plate 100 of the nth layer in the front-back direction is-y 4- (-y3), and Δ y is greater than zero, which indicates that the inner layer plate 100 of the (n + 1) th layer is shifted forward with respect to the inner layer plate 100 of the nth layer, and if the alignment data of the inner layer plate 100 of the (n + 1) th layer with respect to the inner layer plate 100 of the nth layer in the front-back direction is measured as Δ y smaller than.

preferably, step D further comprises the following steps:

step E: subtracting the alignment data of the inner plate 100 in the nth layer from the alignment data of the inner plate 100 in the (n + 1) th layer to calculate the alignment data delta x of the adjacent inner plate 100 in the left-right direction, and measuring the alignment data delta y of the adjacent inner plate 100 in the front-back direction according to the steps;

Step F: utilizing SQRT (delta x ^2 plus delta y ^2) to calculate the alignment data of the adjacent inner-layer plates 100 in the radial direction;

Measuring the alignment data delta x and delta y of the adjacent inner-layer plates 100 in the x direction and the y direction respectively, calculating the alignment data of the adjacent inner-layer plates 100 in the radial direction by using a formula SQRT (delta x ^2 plus delta y ^2), judging whether the alignment data of the adjacent inner-layer plates 100 in the radial direction fall within a required detection range, and further judging whether the product is qualified. This can further improve the detection accuracy.

As shown in fig. 5, preferably, in step C: the front via 231 is the "-" direction test point and the back via 232 is the "+" direction test point. Therefore, after detecting the alignment data Deltay of the adjacent inner-layer boards 100 in the front-back direction, an operator can accurately judge the offset direction of the inner-layer board 100 on the nth layer relative to the inner-layer board 100 on the (n + 1) th layer.

to further enhance the detection accuracy, in another embodiment, in step a: the x-direction detection module 210 and the y-direction detection module 230 are provided in two sets, and the two sets of the x-direction detection module 210 and the y-direction detection module 230 are respectively arranged at diagonal positions of each inner-layer board 100. This makes it possible to perform relatively accurate detection of the alignment accuracy of the inner sheet 100 in the longitudinal direction or the width direction in all aspects. The longitudinal direction means the left-right direction, and the width direction means the front-back direction.

In the step A: in order to reduce the assembly processes and improve the assembly accuracy, the x-direction detection module 210, the y-direction detection module 230 and the inner plate 100 are integrally manufactured and molded.

as shown in fig. 4, preferably, in step C: the left column of vias 211 are "-" direction test points and the right column of vias 212 are "+" direction test points. Therefore, after the alignment data Deltax of the adjacent inner-layer boards 100 in the x direction is detected, an operator can accurately judge the offset direction of the inner-layer board 100 of the nth layer relative to the inner-layer board 100 of the (n + 1) th layer.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and those skilled in the art can make various modifications and variations; any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.