PCB for back drilling alignment detection and manufacturing method thereof

Abstract

The application discloses a PCB for back-drilling alignment degree detection and a manufacturing method thereof, and belongs to the technical field of PCB manufacturing, which comprises the following steps: etching inner layer patterns on an inner layer substrate and laminating to obtain a base plate; drilling holes on the base plate and depositing copper on the drilled holes; deep drilling is performed on the holes after the copper deposition to drill out alignment degree coupons; holes that need to be plugged are plugged with resin; copper is deposited on the hole walls of the unplugged holes; outer layer patterns and a solder mask layer are manufactured; and the back-drilling alignment degree detection precision is improved.

Description

TECHNICAL FIELD

[0001] The application relates to a PCB for back drilling alignment degree detection and a manufacturing method thereof, and belongs to the technical field of PCB manufacturing. BACKGROUND

[0002] With the application and popularization of sever product technology, the size design of a communication product BGA (Ball Grid Array Package) is smaller and smaller, and the distance design from a hole to copper and from a back drilling hole to copper is smaller and smaller. In order to monitor the safe distance from the back drilling to the copper at the BGA, currently, the industry mostly detects through process monitoring or destructive slicing. The whole quality monitoring reaction arc is long, the coverage is low, the cost is high, and the loss rate is high. Therefore, a back drilling alignment degree precision coupon is designed at the four corners of a PCB working panel. The back drilling alignment degree in the PCB can be monitored through electrical measurement of the open / short of the semi-finished product and the finished product, and the back drilling alignment degree capability can also be monitored. The coupon is added to the PCB to facilitate positioning in the PCB production process.

[0003] Currently, the industry adopts a back drilling winding coupon design to achieve the design, that is, a concentric pad (solder pad) larger than the back drilling hole diameter is designed at each layer drilled at the back drilling position. Meanwhile, the pad forms a link with a test hole. After the back drilling is completed, a winding is formed at the hole edge. The principle is to determine the alignment degree and capability of the back drilling through the size design of the pad and whether the winding formed after the back drilling is completed is broken or the link is open / short. If the link is open, it means that the winding is broken, which represents that the back drilling alignment degree has deviated from the set value. If the link is short and the winding is not broken, it means that the back drilling alignment degree is normal. However, the winding design has the following problems in the process, which can cause the actual coupon performance to not truly reflect the back drilling performance at the BGA, and the capability evaluation cannot obtain the actual effect.

[0004] 1. The inner layer design of the PCB at the BGA is different from that of the back drilling winding coupon. The DFM (design for manufacturing) of the winding and the copper residue rate design of the winding coupon can all affect the performance of the winding during the back drilling. Usually, the problems are that the winding of the coupon is larger or smaller than the target value, and the line slip occurs.

[0005] 2. Currently, the open phenomenon can occur during the ET test, but the slicing analysis shows that the back drilling hole is very normal, but the line is missing. In fact, the line is etched. Therefore, the selection of the PCB back drilling time needs to be set according to the product process, so that the winding coupon is locally limited in the application.

[0006] In summary, the accuracy of back-drilling alignment detection needs to be improved. SUMMARY

[0007] The present application aims to provide a PCB for back-drilling alignment detection and a manufacturing method thereof, and solve the problem of low accuracy of back-drilling alignment detection in the prior art.

[0008] To achieve the above object, the present application is implemented by using the following technical solutions:

[0009] In a first aspect, the present application provides a manufacturing method of a PCB for back-drilling alignment detection, comprising:

[0010] Etching inner layer patterns on inner layer substrates and laminating to obtain a base plate;

[0011] Drilling holes on the base plate and depositing copper on the drilled holes;

[0012] Deep drilling on the holes after depositing copper to drill out alignment coupons;

[0013] Plugging the holes that need to be plugged with resin;

[0014] Depositing copper on the hole walls of the unplugged holes;

[0015] Manufacturing outer layer patterns and solder mask layers.

[0016] In combination with the first aspect, further, the laminating comprises: according to a preset structure sequence of the inner layer substrates, using adhesive sheets to paste between each inner layer substrate, and using a hot press to laminate the inner layer substrates together after stacking.

[0017] In combination with the first aspect, further, the drilling comprises drilling through holes for electroplating and press contact / plug-in components by using a numerical control drilling machine.

[0018] In combination with the first aspect, further, the deep drilling comprises deep drilling on the through holes for press contact / plug-in components by using deep plating control drilling.

[0019] In combination with the first aspect, further, the depositing copper comprises depositing >20um of copper on the hole walls by using chemical copper deposition and electroplating copper.

[0020] In combination with the first aspect, further, the manufacturing outer layer patterns and solder mask layers comprises:

[0021] Manufacturing outer layer patterns by using full-plate images or pattern electroplating image transfer;

[0022] Forming solder mask layers according to data by ink coverage.

[0023] In a second aspect, the present application also provides a PCB for back-drilling alignment detection, which is prepared according to any one of the methods in the first aspect.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The present application provides a PCB for back-drilling alignment detection and a manufacturing method thereof. The PCB is prepared by the method of not plugging the hole after drilling and then depositing copper. When the back-drilling alignment detection is performed, the PCB can avoid wire winding slippage, and the back-drilling alignment can be judged and detected by testing the link open / short, so that the alignment level is more effectively and truly reflected. In the manufacturing process, the antipad is better than the traditional wire winding inner layer in terms of size and offset control. The present application overcomes the problem of large or small wire winding of the wire winding coupon design product, and overcomes the problem of wire winding drift caused by slippage during pressing due to the inability to accurately grasp the residual copper rate of the wire winding coupon inner layer. The present application expands the process of the PCB with back-winding coupon design. When the back-drilled via hole is not plugged, or the back-drilling is semi-plugged, the back-drilling timing should be avoided before etching. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a flowchart of a manufacturing method of a PCB for back-drilling alignment detection provided by an embodiment of the present application;

[0027] Figure 2 is a top view of a PCB provided by an embodiment of the present application;

[0028] Figure 3 is a sectional view of a PCB provided by an embodiment of the present application;

[0029] Figure 4 is a schematic diagram of inner layer substrate manufacturing provided by an embodiment of the present application;

[0030] Figure 5 is a schematic diagram of antipad manufacturing provided by an embodiment of the present application;

[0031] Figure 6 is a schematic diagram of back-drilling bottom hole provided by an embodiment of the present application;

[0032] Figure 7 is a schematic diagram of back-drilling bottom hole electroplating provided by an embodiment of the present application;

[0033] Figure 8 is a schematic diagram of back-drilling hole provided by an embodiment of the present application;

[0034] Figure 9 is a schematic diagram of back-drilling hole electroplating provided by an embodiment of the present application;

[0035] Figure 10 is a schematic diagram of outer layer pattern making provided by an embodiment of the present application;

[0036] Figure 11 is a schematic diagram of anti-weld layer making provided by an embodiment of the present application. DETAILED DESCRIPTION

[0037] The present application will be further described below in conjunction with the accompanying drawings, and the following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0038] As shown in Figure 1 , the present application provides a manufacturing method of PCB for back-drilling alignment detection, comprising the following steps:

[0039] (1) Inner layer substrate making: as shown in Figure 4 , according to the structure of the circuit board, the corresponding inner layer board is made, the inner layer pattern 1 is etched on each inner layer substrate by using acid etching through the image transfer of inner layer dry film and inner layer exposure machine.

[0040] (1.1) Data design part, antipad size design D+0.5 / D+1 / D+1.5 / D+2 / D+2.5 / D+3… (Note: considering the copper bite amount of brown oxidation, D is the back-drilling hole diameter, and D+0.5 represents that the antipad is larger than the back-drilling hole diameter by 0.5 mil on one side), and the back-drilling alignment and antipad size are shown in Table 1:

[0041] Table 1-Back-drilling alignment and antipad size comparison table

[0042] Back drill alignment 1 mil 2 mil 3 mil 4 mil 5 mil 6 mil Antipad size D+0.5 D+1 D+1.5 D+2 D+2.5 D+3

[0043] (1.2) Back-drilling alignment coupon inner layer full copper setting, that is, ensuring the network and ensuring the copper residue rate.

[0044] (1.3) The antipad size design can be designed according to the actual ability, such as step (1.1), if the performance of the monitoring product board is monitored, the antipad size can be designed synchronously with the PCB inner CBD2M, and if the capacity test board is designed, it can be designed from small to large in turn, as shown in Figure 5 .

[0045] (2) Inner layer substrate pressing: according to the sequence of the circuit board structure, the circuit board is pressed together by using a hot press, and attention should be paid to the local expansion and contraction of the coupon.

[0046] (3) Outer layer drilling and plating: using a numerical control drilling machine to drill the through holes that need to be plated, and then using chemical copper deposition and electroplating to deposit a certain amount of copper on the hole wall, as shown in Figure 6 and Figure 7 .

[0047] The via hole precision drilled by the numerical control drilling machine needs to be controlled, and the Cpk is controlled to be greater than or equal to 1.33 (the tolerance is set according to the requirement), and the performance of the antipad and the hole is checked by X-ray.

[0048] (4) Deep drilling of holes: the deep drilling of holes is performed on the back drilling coupon and the via hole in the PCB that needs to be back drilled, the corresponding deep-plated hole wall copper is drilled, and the residual copper is detected by the AOI detection equipment, as shown in Figure 8 .

[0049] (5) Resin hole plugging: the resin hole plugging is performed on the via hole and the back drilling hole that needs to be plugged, the via hole in the coupon is not plugged, and the selected plugging can be completed.

[0050] (6) Electroplating capping: the POFV hole is electroplated capping, and the back drilling hole wall of the back drilling coupon is electroplated, so that the bottom hole + back drilling part is conductive to form a link, as shown in Figure 9 .

[0051] After electroplating, the ET tester is used for testing, the open determines that the back drilling is OK under the requirement of the alignment degree, and the short represents NG.

[0052] (7) Outer layer circuit manufacturing: the outer layer pattern is manufactured by using the full plate image or the pattern electroplating image transfer according to the circuit diagram, as shown in Figure 10 .

[0053] (8) Solder mask manufacturing: the corresponding ink coverage is manufactured according to the pattern, as shown in Figure 11 .

[0054] (9) The corresponding finished product is manufactured through the subsequent forming, surface treatment, functional test and other process flows, and the finally manufactured PCB is as shown in Figure 2 and Figure 3 .

[0055] Through actual production verification, the same ET tester is used for testing, the alignment degree detection accuracy of the PCB manufactured by the method provided by the present application can reach 100%, and the alignment degree detection accuracy of the PCB manufactured by the traditional back drilling winding method is only about 80%.

[0056] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the technical field, some improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. A PCB manufacturing method for back-drilling alignment detection, comprising: etching inner layer patterns on inner layer substrates and laminating to obtain base plates; drilling holes on the base plates and depositing copper on the drilled holes; deep drilling on the holes after depositing copper to drill out alignment coupons, including: deep drilling in the alignment coupon position and the via holes requiring back drilling in the PCB using deep drilling, drilling out the copper on the hole wall of the corresponding depth to drill out the alignment coupon; plugging the holes requiring plugging with resin, including: plugging the via holes and back drilling holes with resin, and not plugging the via holes in the alignment coupon; depositing copper on the hole wall of the un-plugged holes, including: electroplating the POFV holes and electroplating the back drilling hole wall of the alignment coupon to make the bottom hole and the back drilling part conductive to form a link; manufacturing outer layer patterns and solder mask layers; the laminating includes: according to the preset structure sequence of the inner layer substrates, using adhesive sheets to paste between each inner layer substrate, and using a hot press to laminate the inner layer substrates together after stacking; the drilling includes drilling the via holes requiring electroplating and requiring crimping / plugging components by a numerical control drilling machine; the deep drilling includes deep drilling on the via holes requiring crimping / plugging components using depth control drilling; the depositing copper includes depositing >20μm of copper on the hole wall using chemical copper deposition and electroplating copper; the manufacturing outer layer patterns and solder mask layers includes: manufacturing outer layer patterns using full plate images or pattern electroplating image transfer; forming solder mask layers according to the patterns.

2. A PCB for back-drilling alignment detection, characterized by, obtained according to the method of claim 1.

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