[0021] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.
[0022] It should be noted that in the following specific embodiments, when the embodiments of the present invention are described in detail, in order to clearly show the structure of the present invention for ease of description, the structure in the drawings is not drawn according to the general scale. Partial enlargement, deformation, and simplification of processing have been implemented. Therefore, this should be avoided as a limitation of the present invention.
[0023] The more important reliability evaluation includes the material test of the circuit board base material, the circuit reliability and mechanical performance reliability of the processed circuit board under extreme environments, and the circuit board base material and circuit board processing parameters match each other. The reliability of the finished circuit board is higher. The invention evaluates the reliability of the finished circuit board made of a specific batch of circuit board substrates using a specific circuit board processing technology.
[0024] In the following specific embodiments of the present invention, please refer to Figure 1 ~ Figure 4. As shown in the figure, a reliability evaluation multilayer circuit board includes a plurality of test areas, each test area includes a drilled area and a hole wall state test area, and the hole diameters of the drilled areas in different test areas are different. The diameter of the test hole in each test area is summarized from the circuit board processing technology.
[0025] Each drilling area includes an array of test holes with the same aperture processed by the same drill bit, starting from the first hole of the test hole array, and for every certain number of test holes processed, a hole wall state test hole is processed in the hole wall state test area . Since the same drill bit is used, the hardness of the circuit board substrate can be indirectly judged by the wear of the drill bit. The test hole array pattern is based on the principle of as many test holes as possible, usually several thousand to tens of thousands.
[0026] The inner wall of the test hole has a conductive layer and a protective layer in turn from the inside to the outside. The test circuit between the test hole and the test hole located between the layers of the multilayer circuit board and the outer layer constitutes a conductive test circuit; the outer layer of the drilled area The circuit board also has two continuity test pads, which are respectively connected to test holes corresponding to the start and end of the conductive test circuit through a wire.
[0027] In this embodiment, the specific implementation of the conductive test circuit refers to figure 2 with image 3 , The conductive test circuit is composed of multiple test circuits in series. The test circuits are evenly distributed in the interlayer and outer layer of the circuit board in the entire drilling area, and the cross-sectional direction along the thickness of the multilayer circuit board in each row of test holes is " V"-shaped polyline distribution. Specifically, taking a 6-layer circuit board as an example, including the L1 to L6 layers, the test circuit is etched on each surface, and the first connectivity test pad 103 is established on the L1 layer of the multilayer circuit board. The continuity test pad 103 is connected to the first hole in the first row of the L1 layer of the laminated circuit board with a wire, and the first hole in the first row of the L1 layer of the laminated circuit board is connected to the length of the test area The second hole of the L2 layer is connected with a test line, and the second hole of the L2 layer of the laminated circuit board is connected with the third hole along the length of the test area with a test line, and then connected to the sixth layer of the L6 layer circuit board. The hole and the seventh hole are connected by a test circuit, and then connected upward in the thickness direction, that is, the seventh hole and the eighth hole of the fifth layer of the laminated circuit board are connected by a test circuit until the test holes in the first row are all connected. Adopt the principle of proximity, connect to the second row of test holes, and then continue to arrange the test lines between the second row of test holes in the same way as the test lines of the first row of test holes between layers in the direction from right to left. Until all the test holes in all rows are connected to the test circuit, the last test hole is connected to the second continuity test pad 105 through a wire. Preferably, the periphery of the test hole is connected to the test circuit through a pad.
[0028] The conductive test circuit is used for circuit continuity testing. The multi-layer circuit board in the drilled area is subjected to a thermal stress test, soaked in a tin-lead pot at 188°C for about 10 seconds, and repeated 3-6 times. Use a resistance tester to test the change rate of the resistance between the two continuity test pads before and after the thermal stress experiment, and evaluate the reliability of the circuit board interlayer and outer circuit according to the resistance change rate. Generally, no more than 2% is considered qualified, or the evaluation is based on industry standards or customer requirements. If the resistance value changes too much, the conductive circuit is disconnected in the destructive experiment. Use a resistance tester to connect any test hole to determine the specific location of the conductive circuit (for example, which layer of circuit board). Due to the large number of test holes, the specific locations where the disconnection occurs are counted, and the statistical results are more reliable, and the process steps represented by the locations where more disconnections occur are the process steps that need improvement.
[0029] Each hole wall state test area includes the same drill bit that processes the test hole. Starting from processing the first test hole, the hole wall state test hole is processed in the hole wall state test area after a certain number of test holes are spaced. Use the multi-layer circuit board in the hole wall state test area to test the impact resistance, abrasion resistance, tear resistance of the circuit board and the bonding strength between different materials. The multi-layer circuit board in the hole wall state test area is subjected to the thermal stress test, and Soak them in a tin-lead pot at 188°C for about 10 seconds, and repeat 3-6 times. Then, the hole wall state test hole is ground half of the hole, and the impact resistance and wear resistance of the circuit board are evaluated by comparing the changes in the hole wall roughness state of the sequentially processed hole wall state test hole. By observing the copper layer and the copper protective layer The bonding state evaluates the bonding strength between the materials, and the tear resistance of the circuit board is evaluated by observing the wick effect between the copper layer and the substrate.
[0030] Since all the holes on this slice are processed by the tool at an interval of 499 holes, it is basically possible to evaluate the state of the hole wall of this type of material under different tool diameters, different tool wear conditions, and different ambient temperatures, and have a certain coverage , Can accurately and scientifically judge the stability of the material's physical properties and chemical properties.
[0031] Since each hole wall state test area needs to be sliced and polished, in order to increase the processing speed, the hole wall state test hole processing positioning hole and the design of slicing to make the positioning hole can be added to the hole wall state test area. Two circuit boards are connected together for grinding, which can improve the grinding efficiency. Hole wall state test hole processing positioning holes and slices to make positioning holes can be processed by drilling technology.
[0032] In order to avoid confusion, a logo design can be added to each drilling area and hole wall state test area, and the logo can be processed by drilling technology.
[0033] The edge of the multilayer circuit board also includes process positioning holes, which is convenient for positioning and use in the circuit board processing technology.
[0034] The method for preparing the reliability evaluation multilayer circuit board includes the following steps:
[0035] Step S1: Design the multilayer circuit board according to the above reliability evaluation, including determining the number of layers of the multilayer circuit board, the number of test areas, the number of rows and columns of the test hole array, the number of test holes, and the number of test holes. The distance between the holes, the position and number of the hole wall state test holes, the inner and outer patterns of the multilayer circuit board, etc.
[0036] Step S2: Perform reliability evaluation of the production of multilayer circuit boards, according to preliminary preparation → engineering design → cutting → blanking → selling → inner layer production → lamination → drilling → electroless plating → electroplating → outer layer pattern production Reliability evaluation multi-layer circuit board is obtained by process steps.
[0037] Step S3: Cut the circuit boards in each drilling area and hole wall state test area, and perform circuit connectivity tests and circuit board impact resistance, abrasion resistance, tear resistance, and bonding strength tests between different materials.
[0038] In summary, the present invention combines multiple important reliability tests in the circuit board processing technology on one reliability test circuit board and completes it through a single processing technology, which can scientifically and accurately make accurate judgments on product reliability. And identification, it has the characteristics of simple operation, reasonable design, capacity control, low manufacturing cost, and obvious effect.
[0039] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Anyone familiar with the technical field within the technical scope disclosed by the present invention, according to the technical solution of the present invention Equivalent replacements or changes to its inventive concept should all fall within the protection scope of the present invention.
