Method for forming bonding pad on printed circuit board, test fixture and test method of packaging structure
The laser cutting technology forms small-pitch pads on the printed circuit board, which solves the problem of difficult to reduce the pad gap, improves the accuracy and processing accuracy of the test signal, and meets the needs of high-density packaging structures.
Patent Information
- Application Number
- CN202411389279.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2024-12-27
AI Technical Summary
The processing technology limitations of existing printed circuit board pads lead to difficulty in shrinking the pad gap, which is prone to short circuits or open circuits, affecting the test accuracy and pin density satisfaction.
Laser cutting technology is used to cut the conductive blocks in the pad group area to form a smaller pad spacing, and the conductive blocks and preset distances are arranged in the mold opening stage to improve machining accuracy and independence.
It realizes precise control of pad spacing, avoids short circuits, improves the integrity and accuracy of test signals, and adapts to the needs of high-density packaging structures.
Smart Images
Figure CN119212235A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of image sensor testing, and in particular to a method for forming a pad on a printed circuit board, a testing fixture, and a testing method for a packaging structure. Background Art
[0002] With the vigorous development of semiconductor technology, the packaging density of integrated circuits (ICs) is getting higher and higher, and the functions are becoming more and more powerful. In the design and testing process of integrated circuits, printed circuit boards (PCBs) play a vital role. The pads on the printed circuit board are the key structures that connect electronic components (such as chips) to the circuit board. They provide electrical connections and mechanical support for the pins of electronic components.
[0003] The pad design on the traditional printed circuit board usually adopts a larger gap to accommodate the wider pin spacing, ensure the reliability of welding and fault tolerance in the production process. However, with the advancement of chip packaging technology, especially for high-performance and high-density chips such as multi-core processors and high-speed memories, the pin spacing is getting smaller and smaller, and the requirements for the design layout and processing accuracy of the pad are also getting higher and higher.
[0004] Due to the limitation of the processing technology of the printed circuit board factory, the processing limit of the pad gap of the printed circuit board is currently around 70μm. This process is mainly limited by the technical limitations of the pad process. The small gap made by the existing technology will cause adhesion between the pads, resulting in a short circuit during the test; and in order to ensure the accuracy of the test, setting a gap that is too large will cause the width of the core pad to be reduced, resulting in poor contact between the chip pins and the printed circuit board, causing an open circuit during the test, affecting the yield, and therefore making it difficult to meet the testing requirements of subsequent chips. Therefore, it is necessary to improve the pad processing method on the printed circuit board.
[0005] It should be understood that the above statements merely provide background technology related to the present invention and do not necessarily constitute prior art. Summary of the invention
[0006] Based on the above technical problems, the purpose of the present invention is to provide a method for forming pads on a printed circuit board, a test fixture, and a test method for a packaging structure. The method for forming pads on a printed circuit board can achieve a smaller pad spacing by cutting the conductive blocks in the pad group area with a laser, while ensuring that each pad is independent of each other, avoiding problems such as short circuits during the test process, and helping the printed circuit board to provide precise electrical connections to ensure the integrity and accuracy of the test signal. On the other hand, since the pad forming method of the present invention can achieve a smaller pad gap, it improves the processing accuracy of the printed circuit board, helps the printed circuit board adapt to a higher pin density, thereby meeting the testing and application requirements of a new generation of high-density packaging structures.
[0007] In order to achieve the above object, the present invention is implemented by the following technical solutions:
[0008] A method for forming a pad on a printed circuit board, comprising:
[0009] In the mold opening stage of the printed circuit board, conductive blocks are arranged one by one in the plurality of pad group areas of the printed circuit board, and the conductive blocks are prepared for subsequent cutting;
[0010] After the mold opening stage of the printed circuit board, the conductive block is cut by laser so that the conductive block is cut off at least at one place to form a plurality of separate pads.
[0011] Optionally, in the mold opening stage, the circuit routing layers of the printed circuit board except for the lead-out or lead-in wires of the pads all bypass the conductive blocks by a preset distance.
[0012] Optionally, the preset distance ranges from 0.25 mm to 0.50 mm.
[0013] Optionally, during the mold opening stage, a conductive anti-oxidation layer is prepared on the surface of the conductive block.
[0014] Optionally, the conductive anti-oxidation layer includes a gold-plated layer.
[0015] Optionally, the laser has a pulse width of femtoseconds; the wavelength range of the laser is 700nm to 1000nm.
[0016] Optionally, the output power range of the laser is 10W to 30W.
[0017] Optionally, before the laser outputs laser to cut the conductive block, the long side of the conductive block is selected to set a positioning edge, so that the laser can cut at different positions marked by the positioning edge.
[0018] Optionally, the printed circuit board has at least two groups of pad group areas.
[0019] Optionally, the at least two groups of pad group areas are distributed around a circumference, and at least part of the pad group areas are symmetrically arranged relative to the circumference.
[0020] Optionally, the conductive blocks arranged on at least two pad group regions have an angle with each other, and the angle ranges from 0° to 90°.
[0021] Optionally, at least part of the pad group area is distributed in a hexagonal structure or a quadrilateral structure on the circumference.
[0022] Optionally, at least one cutting path of the laser can cut the conductive blocks in at least two groups of pad groups.
[0023] Optionally, a test fixture, including:
[0024] A printed circuit board comprises a plurality of pads, wherein the pads are formed by the aforementioned pad forming method on the printed circuit board.
[0025] Optionally, the interval between adjacent pads ranges from 15 μm to 70 μm.
[0026] Optionally, a test method for a package structure,
[0027] The package structure includes a plurality of suspended pins, each of which is respectively matched with at least a portion of discrete pads on the aforementioned test fixture to perform a test on the package structure.
[0028] Compared with the prior art, the present invention has the following advantages:
[0029] In a method for forming pads on a printed circuit board, a test fixture, and a test method for a packaging structure of the present invention, the method for forming pads on the printed circuit board cuts the conductive blocks in the pad group area by laser, and sets a process period for laser cutting implementation, which can achieve a smaller pad spacing at a lower cost, while ensuring that each pad is independent of each other, avoiding problems such as short circuits during the test process, and helping the printed circuit board to provide precise electrical connections to ensure the integrity and accuracy of the test signal. On the other hand, because the pad forming method of the present invention can achieve a smaller pad gap, it improves the processing accuracy of the printed circuit board, helps the printed circuit board adapt to a higher pin density, and thus meets the testing and application requirements of a new generation of high-density packaging structures. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 A schematic diagram of the structure of a printed circuit board of the present invention;
[0031] Figure 2 for Figure 1 Schematic diagram of the simulation layout at A in the middle;
[0032] Figure 3 A schematic diagram of a method for forming a pad on a printed circuit board according to the present invention;
[0033] Figure 4 This is a diagram showing the effect of laser cutting on a printed circuit board of the present invention;
[0034] Figure 5 The figure is a schematic diagram of testing a packaging structure of the present invention on a printed circuit board. DETAILED DESCRIPTION
[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0036] It should be noted that, in this article, the terms "include", "comprises", "has" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "includes..." or "comprising..." do not exclude the existence of other elements in the process, method, article or terminal device including the elements.
[0037] It should be noted that the drawings are all in very simplified form and use inaccurate ratios, and are only used to conveniently and clearly assist in explaining the embodiments of the present invention.
[0038] like Figure 1 and Figure 2 As shown, it is a schematic diagram of the structure of a printed circuit board 100 of the present embodiment. The printed circuit board 100 includes a plurality of pad group areas 110 and positioning holes 120 and other structures. For example, two pad group areas 110 symmetrically arranged along the positioning holes 120 are included in the enlarged area A. Each pad group area 110 includes a plurality of pads 111 separated from each other. The gap between each pad 111 obtained by the pad forming method of the present invention is, for example, about 25 μm. The numbering of each pad 111 is from 1 to 24 in sequence. Each pad 111 is respectively adapted to each suspended pin of the package structure (such as a chip) to test the package structure. However, processing the printed circuit board 100 based on the existing pad 111 processing technology can only minimize the gap between each pad 111 to about 70 μm, and the gap cannot be reduced again. Otherwise, due to the limitation of the processing technology, the adjacent pads 111 will be adhered to each other, resulting in a test short circuit, which affects the use.
[0039] Based on this, the formation method of the pad is introduced in detail below. Figure 3As shown, the present invention provides a method for forming a pad 111 on a printed circuit board 100, the method comprising: in the mold opening stage of the printed circuit board 100, a conductive block is arranged one by one in a plurality of pad group areas 110 of the printed circuit board 100, and the conductive block is prepared for subsequent cutting; in a stage after the mold opening stage of the printed circuit board 100, the conductive block is cut by laser so that the conductive block is cut off at least at one place to form a plurality of discrete pads 111 (see Figure 4 ). By selecting laser cutting to form a number of pads and rationally designing the process period for laser cutting, a relatively small pad spacing can be achieved at a relatively low cost, thereby achieving the effect of reducing costs, increasing efficiency and improving quality of the device. In this embodiment, since laser cutting of the conductive block can be implemented after the mold opening stage, it is conducive to low-cost cooperation of manufacturers. For example, all components of the printed circuit board for testing can be completed in one manufacturer except for the discrete pads (the step of separating the conductive blocks into pads is not performed in this completed state), and manufacturers who need semiconductor testing can directly purchase the finished parts and then use laser cutting to cut the conductive blocks according to their own needs, thereby achieving a smaller pad spacing at a relatively low cost. A smaller gap can facilitate the pad width to be set larger, so as to improve the contact yield between the chip pins and the printed circuit board, avoid open circuits during testing, and improve test quality and efficiency.
[0040] As can be seen from the above, in the method for forming the pad 111 of the present invention, a conductive block is configured in the pad group area 110 during the mold opening stage of the printed circuit board 100, and the conductive block is cut by laser in the stage after the mold opening stage, so that at least one of the conductive blocks is cut off to form separate pads 111. The method can achieve a smaller pad 111 spacing by cutting the conductive block in the pad group area 110 with a laser, that is, to prepare pads 111 with narrower gaps, while ensuring that each pad 111 is independent of each other, avoiding problems such as short circuits during the test process, and helping the printed circuit board 100 to provide precise electrical connections to ensure the integrity and accuracy of the test signal. On the other hand, since the method for forming the pad 111 of the present invention can achieve a smaller pad 111 spacing, the processing accuracy of the printed circuit board 100 is improved, which helps the printed circuit board 100 to adapt to a higher pin density, allowing the printed circuit board 100 to be used for testing of packaging structures with higher pin density, thereby meeting the testing and application requirements of a new generation of high-density packaging structures. Therefore, the improvement of the processing technology of the pad 111 in the present invention is of great significance for the testing of the packaging structure.
[0041] Furthermore, in the mold opening stage, the present invention can make the circuit wiring layers of the printed circuit board 100, except for the lead-out or lead-in wires of the pad 111, bypass the conductive block by a preset distance h (see Figure 2), so that the circuit routing layer other than the lead-out or lead-in line of the pad 111 avoids the conductive block to be cut, reducing the impact on the conductive block to be cut, that is, reducing the impact on the mutual independence of each pad 111 after laser cutting; on the other hand, this method can also realize the regulation of the processing size of the pad group area 110, and then realize the regulation of the size of each pad 111. The present invention combines the laser cutting method with the preset distance h method, which can improve the processing accuracy of the pad 111 on the printed circuit board 100.
[0042] In practical applications, a suitable preset distance h can be set according to requirements. It can be known from practical experience that when setting the preset distance h, a balance needs to be struck between the size of the pad 111 and the independence of the pad 111 to improve the processing accuracy of the printed circuit board 100. Optionally, the range of the preset distance h is 0.25mm to 0.50mm (about 10mil to 20mil). Preferably, while ensuring the independence of each pad 111, the size of each pad 111 is as large as possible so that it can contact the suspended pin of the package structure, thereby improving the accuracy of the test. For example, in one embodiment, when the preset distance h is 0.254mm, the independence and size of each pad 111 have the best synergy effect. It can be understood that the range of the preset distance h is not limited to the above. In other embodiments, it can also be other ranges, and the present invention is not limited to this. On the other hand, the preset distance h between each edge of the conductive block and the adjacent circuit wiring layer can be the same or different. In practical applications, it can be selected according to requirements.
[0043] On the other hand, during the mold opening stage, that is, before laser cutting, a conductive anti-oxidation layer can be prepared on the surface of the conductive block of the printed circuit board 100 to prevent its surface from being oxidized and causing functional degradation, so as to protect the conductive block while having the conductive function, thereby ensuring the stability of each pad 111 separated by subsequent cutting. Optionally, the conductive anti-oxidation layer includes a gold-plated layer. For example, during the mold opening stage, the manufacturer of the printed circuit board 100 uses a gold-plating process on a whole copper sheet in the pad group area 110 to prepare a whole block of conductive blocks of full size. Of course, the conductive anti-oxidation layer may also include other material layers, as long as the corresponding functions can be achieved, and the present invention does not limit this.
[0044] In practical applications, the cutting effect can be regulated by controlling the parameters such as the energy and pulse width of the laser output by the laser, thereby adjusting the gap between each adjacent pad 111. It can be understood that the higher the energy of the laser, the smaller the width of its cutting path, but the energy of the laser is not the higher the better. It is also necessary to consider the safety and economic benefits of the laser in practical applications, and also to avoid excessive damage to the board body of the printed circuit board 100. Optionally, the laser has a femtosecond pulse width; the wavelength range of the laser is 700nm to 1000nm. Based on the above data range, the laser is used to cut the conductive block, so that the width of the cutting path can be 15μm to 70μm, that is, the gap width between each adjacent pad 111 is in the range of 15μm to 70μm. Preferably, the wavelength of the laser is 800nm. On the other hand, the output power of the laser can also be adjusted to regulate the cutting effect. Optionally, the output power range of the laser is 10W to 30W. Preferably, the output power of the laser is 15W. It should be noted that the type of laser, wavelength range, and output power of the laser are not limited to the above. In other embodiments, they can also be other data ranges, and the present invention is not limited to this. Similarly, the range of the gap width between each adjacent pad 111 that can be achieved by cutting the conductive block by laser is not limited to the above. For example, in another embodiment, the gap between each adjacent pad 111 ranges from 20μm to 40μm. Compared with the existing processing technology, this method can reduce the gap between adjacent pads 111 by 30μm to 50μm.
[0045] On the other hand, in the present invention, before the laser is output to cut the conductive block, the long side of the conductive block can be selected to set a positioning edge so that the laser can cut based on different positions marked by the positioning edge, which helps to improve the accuracy of laser cutting positioning, thereby improving the processing accuracy of the printed circuit board 100 and ensuring the accuracy of subsequent tests.
[0046] In the present invention, the printed circuit board 100 has at least two groups of pad group areas 110. In practical applications, the layout design of the printed circuit board 100 can be optimized as needed to reduce signal crosstalk and improve signal integrity.
[0047] Optionally, at least two groups of pad group areas 110 are distributed around a circle, and at least some of the pad group areas 110 are symmetrically arranged relative to the circle. This method not only helps to ensure the independence of each pad group area 110, but also helps to achieve the positioning of each pad group area 110 based on a certain structure, so as to facilitate the positioning during the processing, thereby ensuring the processing accuracy of the printed circuit board 100. For example, Figure 1As shown, the enlarged area at A has two groups of pad group areas 110 , and the two groups of pad group areas 110 are distributed around the circumference of the positioning hole 120 , and the two groups of pad group areas 110 are symmetrically arranged relative to the positioning hole 120 .
[0048] Of course, the distribution of each pad group area 110 is not limited to the above. In other embodiments, it can also be other distribution conditions or ranges, and the present invention is not limited to this. Optionally, the conductive blocks configured on at least two groups of pad group areas 110 have an angle with each other, and the angle ranges from 0° to 90°. In practical applications, it can be set according to requirements to meet the test requirements of different types of packaging structures.
[0049] Based on the above, it can be known that each pad group area 110 on the printed circuit board 100 may have different layout forms. In practical applications, different layout methods may be applied according to needs. Optionally, at least part of the pad group area 110 is distributed in a hexagonal structure or a quadrilateral structure on the circumference, and of course, it can also be distributed in other structures. In the present invention, based on the layout setting of some symmetrically distributed pad group areas 110, at least one laser cutting path of the laser can cut the conductive blocks of at least two groups of pad group areas 110 to improve the utilization efficiency of the laser and save economic costs. At the same time, the symmetry of the pads 111 cut by the corresponding pad group area 110 can be ensured to improve the processing accuracy.
[0050] Based on the same inventive concept, the present invention also provides a test fixture, which includes a printed circuit board 100, and the printed circuit board 100 includes a plurality of pads 111, and the pads 111 are formed by the aforementioned method for forming the pads 111 on the printed circuit board 100. Based on the method for forming the pads 111 of the present invention, while ensuring that the pads 111 on the printed circuit board 100 are separated from each other, the gap between adjacent pads 111 can be reduced, which helps to improve the processing accuracy of the printed circuit board 100, so that the printed circuit board 100 provides precise electrical connection, thereby improving the signal integrity and accuracy of the test fixture test. Optionally, the interval between each adjacent pad 111 ranges from 15μm to 70μm. It can be understood that the test fixture of the present invention may also include structures such as a fixture frame to help support and fix the packaging structure, which will not be repeated here.
[0051] Based on the same inventive concept, the present invention also provides a method for testing a package structure, wherein the package structure includes a plurality of suspended pins, each of which is respectively adapted to at least a portion of the discrete pads 111 on the aforementioned test fixture to perform the test of the package structure. Figure 5As shown, it is a schematic diagram of testing a packaging structure 200 on a printed circuit board 100. The packaging structure 200 in this example is a COM-packaged image sensor, and each suspended pin 210 of the COM-packaged image sensor is in contact with a pad 111 on the printed circuit board 100, so as to implement testing of the COM-packaged image sensor. Of course, the packaging structure can also be other types of devices, and the present invention is not limited to this.
[0052] In summary, in a method for forming a solder pad 111 on a printed circuit board 100 of the present invention, a test fixture, and a test method for a packaging structure, the method for forming a solder pad 111 on the printed circuit board 100 cuts the conductive blocks of the solder pad group area 110 by laser, and sets a process period for laser cutting, which can achieve a smaller spacing between the solder pads 111 at a lower cost, while ensuring that each solder pad 111 is independent of each other, avoiding problems such as short circuits during the test process, and helping the printed circuit board 100 to provide precise electrical connections to ensure the integrity and accuracy of the test signal. On the other hand, because the method for forming the solder pad 111 of the present invention can achieve a smaller gap between the solder pads 111, it improves the processing accuracy of the printed circuit board 100, which helps the printed circuit board 100 adapt to a higher pin density, thereby meeting the testing and application requirements of a new generation of high-density packaging structures.
[0053] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.
Claims
1. A method for forming a pad on a printed circuit board, characterized in that: Include: In the mold opening stage of the printed circuit board, conductive blocks are arranged one by one in the plurality of pad group areas of the printed circuit board, and the conductive blocks are prepared for subsequent cutting; After the mold opening stage of the printed circuit board, the conductive block is cut by laser so that the conductive block is cut off at least at one place to form a plurality of separate pads.
2. The method for forming a pad on a printed circuit board according to claim 1, wherein: In the mold opening stage, the circuit routing layers of the printed circuit board except for the lead-out or lead-in wires of the pads all bypass the conductive blocks by a preset distance.
3. The method for forming a pad on a printed circuit board according to claim 2, wherein: The preset distance ranges from 0.25 mm to 0.50 mm.
4. The method for forming a pad on a printed circuit board according to claim 1, wherein: During the mold opening stage, a conductive anti-oxidation layer is prepared on the surface of the conductive block.
5. The method for forming a pad on a printed circuit board according to claim 4, wherein: The conductive anti-oxidation layer includes a gold-plated layer.
6. The method for forming a pad on a printed circuit board according to claim 1, wherein: The laser has a pulse width of femtosecond level; the wavelength range of the laser is 700nm to 1000nm.
7. The method for forming a pad on a printed circuit board according to claim 1, wherein: The output power of the laser is in the range of 10W to 30W.
8. The method for forming a pad on a printed circuit board according to claim 1, wherein: Before the laser is output to cut the conductive block, the long side of the conductive block is selected to set a positioning edge so that the laser can cut at different positions marked by the positioning edge.
9. The method for forming a pad on a printed circuit board according to claim 1, wherein: The printed circuit board is provided with at least two groups of pad groups.
10. The method for forming a pad on a printed circuit board according to claim 9, wherein: The at least two pad group regions are distributed around a circumference, and at least part of the pad group regions are symmetrically arranged relative to the circumference.
11. The method for forming a pad on a printed circuit board according to claim 9, wherein: The conductive blocks arranged on at least two pad group regions have an angle with each other, and the angle ranges from 0° to 90°.
12. The method for forming a pad on a printed circuit board according to claim 9, wherein: At least part of the pad group area is distributed in a hexagonal structure or a quadrilateral structure on the circumference.
13. The method for forming a pad on a printed circuit board according to claim 9, 10, 11 or 12, characterized in that: At least one cutting path of the laser can cut the conductive blocks in at least two pad group regions.
14. A test fixture, characterized in that: Include: A printed circuit board, comprising a plurality of pads, wherein the pads are formed by the method for forming pads on a printed circuit board as claimed in any one of claims 1 to 13.
15. The test fixture as claimed in claim 14, characterized in that: The interval between adjacent pads ranges from 15 μm to 70 μm.
16. A method for testing a packaging structure, characterized in that: The packaging structure includes a plurality of suspended pins, each of which is respectively matched with at least a portion of discrete pads on the test fixture as described in any one of claims 14 to 15 to perform a test on the packaging structure.