Interlayer alignment method for five-layer LCP circuit board and five-layer LCP circuit board

Abstract

The invention relates to the field of circuit board manufacturing, and particularly discloses an interlayer alignment method for a five-layer LCP circuit board and the five-layer LCP circuit board. A first LCP base material, a second LCP base material, a third LCP base material and a fourth LCP base material are stacked in sequence; each second sight hole in the second piece of LCP base material and each alignment ring on the third piece of LCP base material are positioned in each first sight hole of the first piece of LCP base material, and when the hole edge of the second sight hole in each corner of the second piece of LCP base material is positioned in the corresponding alignment ring of the third piece of LCP base material from each first sight hole of the first piece of LCP base material, the hole edge of the second sight hole in each corner of the second piece of LCP base material is positioned in the corresponding alignment ring of the third piece of LCP base material; and judging that the alignment fitting precision of the second piece of LCP substrate and the third piece of LCP substrate meets the requirement, and through the method, the alignment precision of the circuits between the inner layers of the five-layer LCP circuit board can be visually and accurately identified, the material waste is reduced, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of circuit board manufacturing, and in particular to an interlayer alignment method for a five-layer LCP circuit board and a five-layer LCP circuit board. Background Art

[0002] The inner layers of multi-layer flexible circuit boards have interlayer alignment accuracy requirements. First, the interlayer alignment accuracy of the inner layers directly affects the stability and reliability of the circuit. Any slight deviation may cause a circuit short circuit or functional failure. Especially in a multi-layer structure, accurate alignment between layers is the basis for ensuring the normal operation of the circuit; secondly, the interlayer alignment accuracy of the inner layers has an important impact on the quality of signal transmission. If the interlayer alignment is inaccurate, it may cause signal attenuation, interference and other problems, affecting the overall performance of the circuit; finally, accurate interlayer alignment can reduce subsequent correction work and improve production efficiency. At the same time, accurate alignment can reduce material waste and reduce production costs.

[0003] As disclosed in Chinese patent CN118574338A, a method for measuring interlayer alignment of a multilayer FPC includes steps S1, providing a plurality of circuit boards, each having a first window and a target ring, wherein the target ring is located in the first window area when viewed from above, and the diameters of the target rings of the plurality of circuit boards are different; S2, stacking the plurality of circuit boards to obtain a multilayer FPC board, so that the target rings are arranged in order from approximately small to large according to the diameter, so that after stacking, the target rings of each layer of the circuit board can be observed through the first window of the upper layer of the circuit board; S3, placing the prepared multilayer FPC board on a test bench, using an impact measurement instrument to measure the alignment data of the target ring, obtaining the spacing data between two target rings on adjacent stacked circuit boards, and judging the alignment between the stacked circuit boards based on the obtained spacing data. Through the above method, the alignment data between two adjacent layers of the multi-layer FPC circuit board can be accurately measured, reducing the complexity of production. Since there is no need to judge the alignment by whether the two concentric circles between adjacent layers are tangent, multiple steps of determining the alignment by setting the spacing are omitted, and the alignment data of the circuit board can be measured accurately, quickly and conveniently.

[0004] However, the above method is only applicable to the inter-layer alignment of multi-layer flexible circuit boards made of FPC materials. When the multi-layer flexible circuit boards are made of LCP materials, the above method is not applicable to the inter-layer alignment of multi-layer flexible circuit boards made of LCP materials due to the opaque nature of LCP materials. At present, the industry usually adopts the blind pasting method for multi-layer flexible circuit boards made of LCP materials. After the blind pasting is completed, the product yield is tested through electrical testing. Products that fail the test will be directly scrapped. Since the blind pasting method cannot ensure that the inter-layer wiring accuracy of the inner layer meets the requirements, it results in a high product scrap rate, which increases material waste and production costs. Summary of the invention

[0005] The present invention aims to solve the technical problems existing in the above-mentioned prior art, and provides an interlayer alignment method for a five-layer LCP circuit board and a five-layer LCP circuit board, which can visually and accurately identify the alignment accuracy of the inner layer interlayer lines of the five-layer LCP circuit board, reduce material waste and reduce production costs.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] The interlayer alignment method for a five-layer LCP circuit board described in the present invention comprises the following steps:

[0008] 1) preparing four LCP substrates, which are arranged in sequence as a first LCP substrate, a second LCP substrate, a third LCP substrate and a fourth LCP substrate, wherein the upper side of the first LCP substrate, the upper side of the second LCP substrate and the lower side of the fourth LCP substrate are respectively covered with a copper layer, and both sides of the third LCP substrate are covered with a copper layer;

[0009] 2) First viewing holes penetrating the copper layer and the first LCP substrate are respectively provided at the four corners of the first LCP substrate, second viewing holes penetrating the copper layer and the second LCP substrate are respectively provided at the four corners of the second LCP substrate, and alignment rings penetrating the copper layer are respectively provided at the four corners of the upper surface of the third LCP substrate, the diameter of the second viewing hole and the outer diameter of the alignment ring are both smaller than the diameter of the first viewing hole, and the diameter of the second viewing hole is larger than the inner diameter of the alignment ring and smaller than the outer diameter;

[0010] 3) stacking the first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate in sequence, so that each second viewing hole on the second LCP substrate and each alignment ring on the third LCP substrate are located in each first viewing hole of the first LCP substrate, and when the hole edges of the second viewing holes at each corner of the second LCP substrate are located in the corresponding alignment ring of the third LCP substrate as viewed from each first viewing hole of the first LCP substrate, it is judged that the alignment and bonding accuracy of the second LCP substrate and the third LCP substrate meets the requirements;

[0011] 4) The first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate stacked in sequence are pressed together to form a five-layer LCP circuit board.

[0012] The interlayer alignment method for a five-layer LCP circuit board described in the present invention, since the multi-layer circuit board has high requirements for the alignment accuracy of the interlayer circuits of the inner layer, in the five-layer LCP circuit board, it is only necessary to align the interlayer circuits on the middle two LCP substrates. According to the above method, the alignment and lamination accuracy of the inner layer interlayer circuits of the circuit board made of LCP material can be visually judged, which effectively improves the yield of the five-layer LCP circuit board, improves the efficiency of the circuit board assembly process, reduces material waste and reduces production costs. In addition, part of the copper is removed from the upper surface of the third LCP substrate to form an alignment ring, and an annular groove is formed at the position of the alignment ring relative to the remaining portion of the third LCP substrate that is still covered with a copper layer. When the second LCP substrate is stacked on the third LCP substrate, when looking through the first viewing hole from the top view direction, a color difference is formed between the hole edge of the second viewing hole and the annular groove, which is convenient for rapid and accurate identification and judgment of the alignment and lamination accuracy, and improves the judgment efficiency of the alignment and lamination accuracy.

[0013] Furthermore, in step 2), the four first viewing holes on the first LCP substrate are arranged adjacent to the short side of the first LCP substrate, and the distance between the hole edge of each first viewing hole and the adjacent short side is 2 mm-3 mm.

[0014] Furthermore, in step 2), the alignment ring on the third LCP substrate is formed by an etching process.

[0015] Furthermore, in step 3), when the hole edges of the second viewing holes at each corner of the second LCP substrate are located in the corresponding alignment ring of the third LCP substrate, the hole edges of the second viewing holes are respectively at equal distances from the outer circle of the alignment ring and the inner circle of the alignment ring.

[0016] Furthermore, the distance between the hole edge of the second viewing hole and the outer circle of the alignment ring and the inner circle of the alignment ring are 0.1 mm respectively.

[0017] Furthermore, before step 4), a thermosetting adhesive layer is arranged between the first LCP substrate and the second LCP substrate, between the second LCP substrate and the third LCP substrate, and between the third LCP substrate and the fourth LCP substrate, and heated by a false lamination machine to bond the first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate into one, and the heating temperature is 60°C-80°C.

[0018] Furthermore, before step 4), the stacked first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate are placed on a riveting machine, and riveted at four corners to connect the first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate into one.

[0019] Furthermore, in step 2), the diameter of the first viewing hole is 3 mm-3.5 mm.

[0020] Furthermore, in step 2), the diameter of the second viewing hole is 1.2 mm, the outer diameter of the alignment ring is 1.4 mm, and the inner diameter of the alignment ring is 1 mm.

[0021] A five-layer LCP circuit board described in the present invention comprises a first LCP substrate, a second LCP substrate, a third LCP substrate and a fourth LCP substrate which are connected as one from top to bottom in sequence, first viewing holes penetrating the copper layer and the first LCP substrate are respectively opened at the four corners of the first LCP substrate, second viewing holes penetrating the copper layer and the second LCP substrate are respectively opened at the four corners of the second LCP substrate, alignment rings penetrating the copper layer are respectively opened at the four corners of the upper surface of the third LCP substrate, the diameter of the second viewing hole and the outer diameter of the alignment ring are both smaller than the diameter of the first viewing hole, the diameter of the second viewing hole is larger than the inner diameter of the alignment ring and smaller than the outer diameter; each second viewing hole on the second LCP substrate and each alignment ring on the third LCP substrate are exposed in each first viewing hole of the first LCP substrate, and the hole edges of the second viewing holes at each corner of the second LCP substrate are all located in the corresponding alignment ring of the third LCP substrate.

[0022] The five-layer LCP circuit board described in the present invention can visually judge the alignment and fitting accuracy of the inner layer interlayer circuits of the LCP circuit board through the above structure when the first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate are only in a stacked state but not in a connected state, effectively improving the yield of the molded product, improving the efficiency of the circuit board assembly process, reducing material waste and reducing production costs. In addition, part of the copper is removed from the upper surface of the third LCP substrate to form an alignment ring, and an annular groove is formed at the position of the alignment ring relative to the remaining portion of the third LCP substrate that is still covered with a copper layer. When the second LCP substrate is stacked on the third LCP substrate, when looking through the first viewing hole from a top view direction, a color difference is formed between the hole edge of the second viewing hole and the annular groove, which is convenient for rapid and accurate identification and judgment of the alignment and fitting accuracy, and improves the judgment efficiency of the alignment and fitting accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other purposes, features and advantages of the present invention will become more clear by more specific description of the preferred embodiments of the present invention shown in the accompanying drawings. The same reference numerals indicate the same parts in all the accompanying drawings, and the accompanying drawings are not deliberately scaled to the actual size, and the focus is on illustrating the main purpose of the present invention.

[0024] Figure 1 It is a top view of the present invention.

[0025] Figure 2 for Figure 1 A partial enlarged view of part A.

[0026] Figure 3 for Figure 1 Partial cross-sectional view along the BB direction (LCP substrates are not bonded together).

[0027] Among them, there are a first LCP substrate 1 ; a second LCP substrate 2 ; a third LCP substrate 3 ; a fourth LCP substrate 4 ; a first viewing hole 5 ; a second viewing hole 6 ; and an alignment ring 7 . DETAILED DESCRIPTION

[0028] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below with reference to the relevant drawings.

[0029] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to another element and integrated therewith, or there may be an intermediate element at the same time. The terms "installed", "one end", "the other end" and similar expressions used herein are for illustrative purposes only.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art. The terms used in the specification herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0031] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0032] In the description of this specification, the description with reference to the terms "preferred embodiment", "further embodiment", "other embodiments" or "specific example" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0033] The present invention specifically provides an embodiment of an interlayer alignment method for a five-layer LCP circuit board, comprising the following steps: Step (1), preparing four LCP substrates, which are arranged in sequence as a first LCP substrate 1, a second LCP substrate 2, a third LCP substrate 3 and a fourth LCP substrate 4, wherein a copper layer (i.e., a Cu layer) is respectively coated on an upward side of the first LCP substrate 1, an upward side of the second LCP substrate 2 and a downward side of the fourth LCP substrate 4, and a copper layer is coated on both sides of the third LCP substrate 3; the copper layer of the second LCP substrate 2 and the copper layer of the third LCP substrate 4 are coated on the copper layer of the third LCP substrate 3; Circuit layers are etched on the copper layers on both sides of 3, respectively. Since circuit layers are etched on the two, respectively, there is a requirement for interlayer bonding accuracy between the second LCP substrate 2 and the third LCP substrate 3 to ensure that the formed circuit board can be used normally; in addition, the five-layer LCP circuit board referred to in the present invention is mainly determined by the number of copper layers. The total number of copper layers on the first LCP substrate 1, the second LCP substrate 2, the third LCP substrate 3 and the fourth LCP substrate 4 is five layers, so the circuit board finally formed is a five-layer circuit board; in addition, the "upward" and "downward" mentioned in the present invention are both based on Figure 1 The view state is used as a reference. When the view direction changes, the orientation also changes accordingly.

[0034] Step (2), first viewing holes 5 penetrating the copper layer and the first LCP substrate 1 are respectively opened at the four corners of the first LCP substrate 1, and the first viewing holes 5 are used to provide a premise for visual judgment, that is, to expose the second viewing holes 6 of the second LCP substrate 2 and the alignment ring 7 of the third LCP substrate 3; second viewing holes 6 penetrating the copper layer and the second LCP substrate 2 are respectively opened at the four corners of the second LCP substrate 2, and alignment rings 7 penetrating the copper layer are respectively opened at the four corners of the upper surface of the third LCP substrate 3, and the diameter of the second viewing hole 6 and the outer diameter of the alignment ring 7 are both smaller than the diameter of the first viewing hole 5, so as to ensure that the second viewing hole 6 and the alignment ring 7 can be exposed in the first viewing hole 5; the diameter of the second viewing hole 6 is larger than the inner diameter of the alignment ring 7 and smaller than the outer diameter; in addition, the first viewing hole 5 on the first LCP substrate 1 The second viewing hole 6 on the second LCP substrate can be obtained by mechanical punching, and the position accuracy of the first viewing hole 5 and the second viewing hole 6 at each corner is automatically determined by the punching machine, that is, the CAD drawing of the circuit board can be imported into the punching machine, so that the punching machine can automatically confirm the precise positions of the first viewing hole 5 and the second viewing hole 6 on the corresponding LCP substrate board according to the CAD drawing, and automatically punch, and by confirming the positions of the first viewing hole 5 and the second viewing hole 6, preliminary preparations are made for the recognition and judgment of the alignment accuracy when the substrates are subsequently stacked; the alignment ring 7 formed on the third LCP substrate 3 is mainly realized by etching equipment, and by importing the CAD drawing into the etching equipment, the etching equipment can automatically confirm the precise position of the alignment ring 7 on the third LCP substrate 3 according to the CAD drawing, and automatically etch to form the alignment ring 7.

[0035] Step (3), stacking the first LCP substrate 1, the second LCP substrate 2, the third LCP substrate 3 and the fourth LCP substrate 4 in sequence, so that each second viewing hole 6 on the second LCP substrate 2 and each alignment ring 7 on the third LCP substrate 3 are located in each first viewing hole 5 of the first LCP substrate 1. When the hole edges of the second viewing holes 6 at each corner of the second LCP substrate 2 are all located in the corresponding alignment ring 7 of the third LCP substrate 3, it is judged that the alignment and bonding accuracy of the second LCP substrate 2 and the third LCP substrate 3 meets the requirements. It can be understood that the hole edges of the second viewing holes 6 are located between the inner circle and the outer circle of the corresponding alignment ring 7 of the third LCP substrate 3, and it is judged that the alignment and bonding accuracy of the second LCP substrate 2 and the third LCP substrate 3 meets the requirements; if it does not meet the alignment and bonding accuracy requirements, it can be readjusted to improve the product yield. The relative position of the second viewing hole 6 and the corresponding alignment ring 7 can be judged manually, but this method is too inefficient. It can also be judged by visual equipment such as CCD, which has high judgment efficiency and high accuracy. Figure 2 Make an explanation, Figure 2Since the alignment ring on the third LCP substrate 3 is only an annular groove with part of the copper etched away, when looking through the first viewing hole 5 and the second viewing hole 6, what is exposed is the upper surface of the third LCP substrate 3 covered with the copper layer. Since the diameter of the second viewing hole 6 on the second LCP substrate is larger than the inner diameter of the alignment ring on the third LCP substrate but smaller than the outer diameter of the alignment ring on the third LCP substrate, when looking from the second viewing hole 6 to the third LCP substrate 3, a part of the alignment ring is blocked by the second LCP substrate 2, and is therefore represented by a dotted circle. At the same time, in order to highlight the position of the alignment ring, the unblocked part is highlighted with dense lines.

[0036] Step (4) is to press the first LCP substrate 1, the second LCP substrate 2, the third LCP substrate 3 and the fourth LCP substrate 4 stacked in sequence to form a five-layer LCP circuit board. The so-called pressing is to press all the LCP substrates into a whole at a high temperature by a pressing device so that adjacent LCP substrates are closely attached.

[0037] Since the dotted lines of the multi-layer circuit board are first etched on the inner substrate board, the alignment accuracy of the inner layer interlayer circuits is required to be high. In the five-layer LCP circuit board, it is only necessary to align the interlayer circuits on the middle two LCP substrates. According to the above method, the alignment and bonding accuracy of the inner layer interlayer circuits of the LCP material circuit board can be visually judged, which effectively improves the yield of the five-layer LCP circuit board, improves the efficiency of the circuit board assembly process, reduces material waste and reduces production costs. In addition, part of the copper is removed from the upper surface of the third LCP substrate 3 to form an alignment ring 7, and an annular groove is formed at the position of the alignment ring 7 relative to the remaining portion of the third LCP substrate 3 that is still covered with the copper layer, that is, the alignment ring 7 can be understood as an annular groove, that is, a part of the copper is removed by etching on the copper layer on the upper surface of the third LCP substrate 3, thereby forming an annular groove, that is, the alignment ring 7; when the second LCP substrate 2 is stacked on the third LCP substrate 3, when viewed from the top direction through the first viewing hole 5, a color difference is formed between the hole edge of the second viewing hole 6 and the annular groove. When viewed from the top direction, the upper surface of the second LCP substrate 2 is covered with a copper layer and has a copper color, and since the copper layer is removed at the annular groove of the third LCP substrate 3, the color thereat is the color of the LCP substrate, thereby forming a color difference, which is convenient for quickly and accurately identifying and judging the alignment and bonding accuracy, thereby improving the judgment efficiency of the alignment and bonding accuracy.

[0038] In a preferred embodiment, in step (2), four first viewing holes 5 on the first LCP substrate 1 are arranged adjacent to the short side of the first LCP substrate 1, and the distance between the hole edge of each first viewing hole 5 and the adjacent short side is 2mm-3mm, such as 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm or 3mm, etc. It can be understood that the distance between the first viewing hole 5 and the short side of the first LCP substrate 1 is smaller than the distance between the first viewing hole 5 and the field edge of the first LCP substrate 1. Since the LCP substrate has more waste areas on the short side, it can provide space for the first viewing hole 5, and also avoid the problem of bursting when punching.

[0039] In a preferred embodiment, in step (3), when the hole edges of the second viewing holes 6 at each corner of the second LCP substrate 2 are located in the corresponding alignment ring 7 of the third LCP substrate 3, the hole edges of the second viewing holes 6 are respectively at equal distances from the outer circle of the alignment ring 7 and the inner circle of the alignment ring 7. Specifically, the diameter of the second viewing hole 6 is 1.2 mm, the outer circle diameter of the alignment ring 7 is 1.4 mm, the inner circle diameter of the alignment ring 7 is 1 mm, and the hole edges of the second viewing holes 6 are respectively at equal distances from the outer circle of the alignment ring 7 and the inner circle of the alignment ring 7, so that it can be confirmed that the interlayer circuit bonding alignment accuracy of the second LCP substrate 2 and the third LCP substrate 3 is within 0.1 mm. Of course, the spacing between the inner circle and the outer circle of the alignment ring 7 on the third LCP substrate 3 can also be adjusted according to the bonding accuracy requirements of the actual product.

[0040] In a preferred embodiment, before step (4), it is necessary to preliminarily fix multiple LCP substrates whose alignment and bonding accuracy is judged to meet the requirements to avoid displacement between adjacent LCP substrates. In view of the fact that the LCP material itself has no stickiness, two specific methods of preliminary fixing are provided in the present invention. The first method is: a thermosetting adhesive layer is provided between the first LCP substrate 1 and the second LCP substrate 2, between the second LCP substrate 2 and the third LCP substrate 3, and between the third LCP substrate 3 and the fourth LCP substrate 4, and heated by a false bonding machine to bond the first LCP substrate 1, the second LCP substrate 2, the third LCP substrate 3 and the fourth LCP substrate 4 together, and the heating temperature is 60°C-80°C. Since the LCP material itself has a high melting point, the method of using a soldering iron for preliminary fixing is not suitable for LCP material. The second method: Place the stacked first LCP substrate 1, the second LCP substrate 2, the third LCP substrate 3 and the fourth LCP substrate 4 on a riveting machine, and rivet them at the four corners to fix them, so as to preliminarily fix and connect the first LCP substrate 1, the second LCP substrate 2, the third LCP substrate 3 and the fourth LCP substrate 4 as a whole. The riveted area is also the waste area. The above method can be used to prepare for the lamination process in step (4) to ensure that the lamination of the multi-layer flexible circuit board is normal. In the method of fixing with rivets, the plastic rivets will soften and deform due to the high temperature during the subsequent lamination. For this reason, the waste area of ​​the five-layer flexible circuit board that has been lamination is trimmed to remove the rivets. When the first method is used, the thermosetting adhesive layer needs to be coated on the surface of the corresponding LCP substrate in step (1). Since the thermosetting adhesive has color, in order to avoid affecting the judgment in step (3), in step (2), through holes should be opened on the thermosetting adhesive layer between the first LCP substrate 1 and the second LCP substrate 2 and on the thermosetting adhesive layer between the second LCP substrate 2 and the third LCP substrate 3 to expose the second viewing hole 6 and the alignment ring 7. There is no requirement for the size of the through hole on the thermosetting adhesive layer, which only needs to be able to expose the second viewing hole 6 and the alignment ring 7.

[0041] In a preferred embodiment, in step (2), the diameter of the first viewing hole 5 is 3 mm-3.5 mm, which can ensure that the second viewing hole 6 and the alignment ring 7 thereunder are fully exposed, providing a good basis for determining the relative positions of the second viewing hole 6 and the alignment ring 7.

[0042] The present invention also provides a specific embodiment of a five-layer LCP circuit board, see Figure 1-3The five-layer LCP circuit board can use the above-mentioned interlayer alignment method to realize the judgment and detection of the alignment and lamination accuracy of the inner layer interlayer circuit; the five-layer LCP circuit board includes a first LCP substrate 1, a second LCP substrate 2, a third LCP substrate 3 and a fourth LCP substrate 4 which are connected as a whole from top to bottom in sequence, and first viewing holes 5 penetrating the copper layer and the first LCP substrate 1 are respectively opened at the four corners of the first LCP substrate 1, and second viewing holes 6 penetrating the copper layer and the second LCP substrate 2 are respectively opened at the four corners of the second LCP substrate 2, and the third LCP substrate 4 is provided with a plurality of first viewing holes 5 penetrating the copper layer and the first LCP substrate 1. The four corners of the upper surface of the LCP substrate 3 are respectively provided with alignment rings 7 penetrating the copper layer, the diameter of the second viewing hole 6 and the outer diameter of the alignment ring 7 are both smaller than the diameter of the first viewing hole 5, the diameter of the second viewing hole 6 is larger than the inner diameter of the alignment ring 7 and smaller than the outer diameter; each second viewing hole 6 on the second LCP substrate 2 and each alignment ring 7 on the third LCP substrate 3 are exposed in each first viewing hole 5 of the first LCP substrate 1, and the hole edges of the second viewing holes 6 on each corner of the second LCP substrate 2 are all located in the corresponding alignment ring 7 of the third LCP substrate 3. Through the above structure, the alignment and bonding accuracy of the inner layer interlayer circuits of the LCP material circuit board can be visually judged, which effectively improves the yield of the five-layer LCP circuit board, improves the efficiency of the circuit board assembly process, reduces material waste and reduces production costs. In addition, part of the copper is removed from the upper surface of the third LCP substrate 3 to form an alignment ring 7, and an annular groove is formed at the position of the alignment ring 7 relative to the remaining portion of the third LCP substrate 3 that is still covered with the copper layer. When the second LCP substrate 2 is stacked on the third LCP substrate 3, when viewed from a top view, the upper surface of the second LCP substrate 2 is covered with a copper layer and has a copper color, and since the copper layer is removed from the annular groove of the third LCP substrate 3, the color therein is the color of the LCP substrate, thereby forming a color difference, which is convenient for quickly and accurately identifying and judging the alignment and bonding accuracy, thereby improving the efficiency of judging the alignment and bonding accuracy.

[0043] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for interlayer alignment of a five-layer LCP circuit board, characterized in that: The steps include: 1) preparing four LCP substrates, which are arranged in sequence as a first LCP substrate, a second LCP substrate, a third LCP substrate and a fourth LCP substrate, wherein the upper side of the first LCP substrate, the upper side of the second LCP substrate and the lower side of the fourth LCP substrate are respectively covered with a copper layer, and both sides of the third LCP substrate are covered with a copper layer; 2) First viewing holes penetrating the copper layer and the first LCP substrate are respectively provided at the four corners of the first LCP substrate, second viewing holes penetrating the copper layer and the second LCP substrate are respectively provided at the four corners of the second LCP substrate, and alignment rings penetrating the copper layer are respectively provided at the four corners of the upper surface of the third LCP substrate, the diameter of the second viewing hole and the outer diameter of the alignment ring are both smaller than the diameter of the first viewing hole, and the diameter of the second viewing hole is larger than the inner diameter of the alignment ring and smaller than the outer diameter; 3) stacking the first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate in sequence, so that each second viewing hole on the second LCP substrate and each alignment ring on the third LCP substrate are located in each first viewing hole of the first LCP substrate, and when the hole edges of the second viewing holes at each corner of the second LCP substrate are located in the corresponding alignment ring of the third LCP substrate as viewed from each first viewing hole of the first LCP substrate, it is judged that the alignment and bonding accuracy of the second LCP substrate and the third LCP substrate meets the requirements; 4) The first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate stacked in sequence are pressed together to form a five-layer LCP circuit board.

2. The interlayer alignment method for a five-layer LCP circuit board according to claim 1, characterized in that: In step 2), the four first viewing holes on the first LCP substrate are arranged adjacent to the short side of the first LCP substrate, and the distance between the hole edge of each first viewing hole and the adjacent short side is 2 mm-3 mm.

3. The interlayer alignment method for a five-layer LCP circuit board according to claim 1, characterized in that: In step 2), the alignment ring on the third LCP substrate is formed by an etching process.

4. The interlayer alignment method for a five-layer LCP circuit board according to claim 1, characterized in that: In step 3), when the hole edges of the second viewing holes at each corner of the second LCP substrate are located in the corresponding alignment rings of the third LCP substrate, the hole edges of the second viewing holes are respectively at equal distances from the outer circle and the inner circle of the alignment ring.

5. The interlayer alignment method for a five-layer LCP circuit board according to claim 4 is characterized in that: The distance between the hole edge of the second viewing hole and the outer circle of the alignment ring and the inner circle of the alignment ring are 0.1 mm respectively.

6. The interlayer alignment method for a five-layer LCP circuit board according to claim 1, characterized in that: Before step 4), a thermosetting adhesive layer is arranged between the first LCP substrate and the second LCP substrate, between the second LCP substrate and the third LCP substrate, and between the third LCP substrate and the fourth LCP substrate, and heated by a false lamination machine to bond the first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate together, and the heating temperature is 60°C-80°C.

7. The interlayer alignment method for a five-layer LCP circuit board according to claim 1, characterized in that: Before step 4), the stacked first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate are placed on a riveting machine and riveted at four corners to connect the first LCP substrate, the second LCP substrate, the third LCP substrate and the fourth LCP substrate into one.

8. The interlayer alignment method for a five-layer LCP circuit board according to claim 1, characterized in that: In step 2), the diameter of the first viewing hole is 3 mm-3.5 mm.

9. The interlayer alignment method for a five-layer LCP circuit board according to claim 1, characterized in that: In step 2), the diameter of the second viewing hole is 1.2 mm, the outer diameter of the alignment ring is 1.4 mm, and the inner diameter of the alignment ring is 1 mm.

10. A five-layer LCP circuit board, characterized in that: The invention comprises a first LCP substrate, a second LCP substrate, a third LCP substrate and a fourth LCP substrate which are connected as a whole from top to bottom in sequence, wherein first viewing holes penetrating the copper layer and the first LCP substrate are respectively provided at the four corners of the first LCP substrate, second viewing holes penetrating the copper layer and the second LCP substrate are respectively provided at the four corners of the second LCP substrate, and alignment rings penetrating the copper layer are respectively provided at the four corners of the upper surface of the third LCP substrate, wherein the diameter of the second viewing hole and the outer diameter of the alignment ring are both smaller than the diameter of the first viewing hole, and the diameter of the second viewing hole is larger than the inner diameter of the alignment ring and smaller than the outer diameter; each second viewing hole on the second LCP substrate and each alignment ring on the third LCP substrate are exposed in each first viewing hole of the first LCP substrate, and the hole edges of the second viewing holes at each corner of the second LCP substrate are all located in the corresponding alignment ring of the third LCP substrate.

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