A Blind Hole Reliability Testing Method, Device, Apparatus and System

Abstract

The present invention relates to a blind hole reliability testing method, equipment, device and system, the method comprising: directing a laser beam toward a circuit board and performing laser heating on the blind hole to apply a thermal field and form a temperature gradient; performing electrical testing, mechanical testing or metallographic testing on the blind hole to determine the reliability of the electrical connection between the conductive column of the connection hole and the lower conductive layer or / and the upper conductive layer. The present invention uses local high-temperature heating with a laser beam to perform energy-saving, efficient, and full-inspection online blind hole reliability testing on the mechanical and electronic connection between the electroplated metal at the bottom of the blind hole and the original metal, filling a global industry gap and allowing the industry to no longer be afraid of blind holes in circuit boards. At the same time, according to the principles of the present invention, due to the existence of a temperature gradient, the local heating temperature of the electroplated metal in the blind hole can be much higher than the temperature that the insulating material of the intermediate insulating layer can withstand. The strictness of the test is much higher than the current industry temperature cycle box test, and has more reliable test results.

Description

Technical Field

[0001] The present invention relates to the field of blind via testing of circuit boards, and in particular to a blind via reliability testing method, equipment, device and system. Background Art

[0002] Blind vias have been a topic of dread in the circuit board industry for decades. The key issue is that existing blind via production methods make it difficult to control residual adhesive and copper-carbon alloys at the bottom of the vias. Once discovered, large quantities of products will be scrapped, resulting in heavy losses. Existing blind via control relies on empirical control and random sampling inspections, which are treading on thin ice, and random sampling inspections are always destructive inspections. Currently, random sampling inspections in the industry primarily involve temperature cycling shock testing. Other AOI inspections during the production process only check for residual adhesive at the bottom of the vias and do not inspect metal and carbon alloys (such as copper-carbon alloys) at the bottom of the blind vias. Four-wire testing after electroplating also only checks for residual adhesive at the bottom of the vias. If it is just copper-carbon alloy, the conductivity will not change significantly, so the four-wire inspection will not detect the problem. However, the presence of copper-carbon alloy at the bottom of the blind via is itself a fatal problem.

[0003] In the current PCB industry, blind via reliability testing is essential for any circuit board, whether it's flexible, rigid, rigid-flex, carrier, high-frequency, high-speed, AI, or automotive. Current blind via reliability testing typically utilizes temperature cycling, with some employing cycles from sub-zero to high temperatures, while others employ temperature cycling from 50°C to 245°C or even 260°C. To maintain temperature balance across the entire circuit board, these cycles are very slow; typically, one cycle per hour is considered relatively fast. Performing 30 cycles at this rate is time-consuming. Furthermore, these tests cannot be conducted online on the PCB production line, but rather require individual offline sampling in a physical laboratory. Furthermore, comprehensive blind via reliability testing is impossible. The industry urgently needs a method to detect and fully inspect blind vias containing residual adhesive or copper-carbon alloy at the bottom of the vias to completely prevent blind via accidents. Summary of the Invention

[0004] The present invention provides a blind hole reliability testing method, equipment, device and system, which can solve the industry pain point problem that blind hole reliability testing cannot achieve online, efficient and full inspection testing.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] In a first aspect, the present invention provides a blind via reliability testing method, which performs a reliability test on a blind via on a circuit board, wherein the circuit board comprises at least a stacked lower conductive layer, an intermediate insulating layer, and an upper conductive layer; a connecting hole conductive post is provided in the blind via, the connecting hole conductive post penetrates the intermediate insulating layer, and connects to the upper conductive layer at the opening of the blind via and to the lower conductive layer at the bottom of the blind via;

[0007] The blind hole reliability testing method comprises:

[0008] Step 1: Directing a laser beam toward the circuit board and aiming at the blind hole for laser heating to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive pillar of the connection hole, and the lower conductive layer, and simultaneously forming a temperature gradient between the conductive area of the circuit board and the intermediate insulating layer surrounding the blind hole;

[0009] The temperature gradient and temperature level of the thermal field are controlled by controlling the heating speed and intensity of the laser beam; the thermal field temperature of the connecting hole conductive pillar is lower than the melting temperature of the connecting hole conductive pillar; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive pillar and the upper conductive layer and the lower conductive layer;

[0010] Step 2: performing electrical testing, mechanical testing, or metallographic testing on the blind via to determine the reliability of the electrical connection between the conductive pillar in the connection hole and the lower conductive layer and / or the upper conductive layer.

[0011] In a second aspect, the present invention provides a blind hole reliability testing device for performing reliability testing on blind holes on a circuit board, wherein the circuit board comprises at least a stacked lower conductive layer, an intermediate insulating layer, and an upper conductive layer; a connecting hole conductive post is provided in the blind hole, the connecting hole conductive post penetrates the intermediate insulating layer, and connects to the upper conductive layer at the opening of the blind hole and to the lower conductive layer at the bottom of the blind hole;

[0012] The blind hole reliability testing equipment comprises:

[0013] A motion platform, which is used to carry the circuit board and drive the circuit board to move;

[0014] A positioning module, used to locate the circuit board on the motion platform and obtain positioning information;

[0015] a laser for generating a laser beam;

[0016] a galvanometer scanning and flat-field focusing device, connected to the laser and the positioning module, for performing galvanometer scanning and flat-field focusing on the laser beam and outputting the laser beam, and directing the output laser beam toward the circuit board according to the positioning information, and performing laser heating on the blind hole to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive pillar of the connection hole, and the lower conductive layer, and simultaneously forming a temperature gradient between the conductive area of the circuit board and the intermediate insulating layer surrounding the blind hole;

[0017] The temperature gradient and temperature level of the thermal field are controlled by controlling the heating speed and intensity of the laser beam; the thermal field temperature of the connecting hole conductive pillar is lower than the melting temperature of the connecting hole conductive pillar; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive pillar and the upper conductive layer and the lower conductive layer;

[0018] A testing module is used to perform electrical testing, mechanical testing, or metallographic testing on the blind via to determine the reliability of the electrical connection between the conductive column in the connection hole and the lower conductive layer and / or the upper conductive layer.

[0019] In a third aspect, the present invention provides a blind hole reliability testing device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the computer program implements the blind hole reliability testing method as described above when executed.

[0020] In a fourth aspect, the present invention provides a blind hole reliability testing system, comprising a machine platform, a laser, and the blind hole reliability testing device as described above, wherein the blind hole reliability testing device is electrically connected to the laser;

[0021] The machine is used to carry the circuit board to be processed;

[0022] The laser is used to generate a laser beam;

[0023] The blind hole reliability testing device is used to control the laser beam generated by the laser to be directed toward the circuit board, and to perform laser heating on the blind hole on the circuit board to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive pillar of the connection hole, and the lower conductive layer, and at the same time forming a temperature gradient between the conductive area of the circuit board and the intermediate insulating layer surrounding the blind hole;

[0024] The temperature gradient and temperature level of the thermal field are controlled by controlling the heating speed and intensity of the laser beam; the thermal field temperature of the connecting hole conductive pillar is lower than the melting temperature of the connecting hole conductive pillar; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive pillar and the upper conductive layer and the lower conductive layer;

[0025] The blind vias are subjected to electrical testing, mechanical testing, or metallographic testing to determine the reliability of the electrical connection between the conductive pillars in the connection holes and the lower conductive layer and / or the upper conductive layer.

[0026] The beneficial effects of the present invention are as follows: a blind hole reliability testing method, equipment, device and system of the present invention uses local high-temperature heating with a laser beam to perform energy-saving, high-efficiency, and full-inspection online blind hole reliability testing on the mechanical and electronic connections between the electroplated metal at the bottom of the blind hole and the original metal, filling a global industry gap and allowing the industry to no longer be afraid of blind holes in circuit boards; at the same time, according to the principles of the present invention, due to the existence of a temperature gradient, the local heating temperature of the electroplated metal in the blind hole can be much higher than the temperature that the insulating material of the intermediate insulating layer can withstand. The strictness of the test is much higher than the current industry's temperature cycling chamber test, and it has more reliable test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a blind hole reliability test method of the present invention;

[0028] Figure 2 An example diagram for implementing a reliability test on a blind via on a circuit board;

[0029] Figure 3 Another example diagram for implementing a reliability test on a blind via on a circuit board;

[0030] Figure 4 for Figure 2 The reliability test failure diagram shown;

[0031] Figure 5 for Figure 2 The reliability test shown is passed in the schematic diagram;

[0032] Figure 6 for Figure 3 The reliability test failure diagram shown;

[0033] Figure 7 for Figure 3 The reliability test shown is passed in the schematic diagram;

[0034] Figure 8 is the cross-section of the second-order blind hole;

[0035] Figure 9 It is a cross-sectional view of stacked holes;

[0036] Figure 10 This is a cross-layer pore cross-section.

[0037] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0038] 1. Lower conductive layer; 2. Intermediate insulating layer; 3. Upper conductive layer; 4a. Blind hole; 4b. Connecting hole conductive column; 5. Crystal interface; 6. Surface electroplating layer; 7. Laser beam; 8. Thermal field; 9. Gap; 11. Third conductive layer; 12. Cross-layer insulating layer; 21. Second intermediate insulating layer; 22. Third intermediate insulating layer; 111. Fourth conductive layer. DETAILED DESCRIPTION

[0039] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0040] Example 1:

[0041] A blind via reliability testing method is disclosed, wherein a blind via on a circuit board is reliability tested. The circuit board comprises at least a stacked lower conductive layer, an intermediate insulating layer, and an upper conductive layer, wherein the bottom of the blind via is the lower conductive layer. A connecting hole conductive post is provided in the blind via, the connecting hole conductive post passing through the intermediate insulating layer and connected to the upper conductive layer at the opening of the blind via and to the lower conductive layer at the bottom of the blind via.

[0042] like Figure 1 As shown, the blind hole reliability testing method includes:

[0043] Step 1: Directing a laser beam toward the circuit board and aiming at the blind hole for laser heating to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive pillar of the connection hole, and the lower conductive layer, and simultaneously forming a temperature gradient between the conductive area of the circuit board and the intermediate insulating layer surrounding the blind hole;

[0044] The temperature gradient and temperature level of the thermal field are controlled by controlling the heating speed and intensity of the laser beam; the thermal field temperature of the connecting hole conductive pillar is lower than the melting temperature of the connecting hole conductive pillar; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive pillar and the upper conductive layer and the lower conductive layer;

[0045] Step 2: performing electrical testing, mechanical testing, or metallographic testing on the blind via to determine the reliability of the electrical connection between the conductive pillar in the connection hole and the lower conductive layer and / or the upper conductive layer.

[0046] Specifically, such as Figure 2 or Figure 3As shown, the circuit board includes a lower conductive layer 1, an intermediate insulating layer 2, and an upper conductive layer 3. Blind vias 4a are machined on the upper conductive layer 3. The blind vias 4a pass through the intermediate insulating layer 2, and the bottom of the vias is the surface of the lower conductive layer 1. After the circuit board is subjected to black hole or black shadow or chemical copper deposition, the lower conductive layer 1 and the upper conductive layer 3 have conductive properties. Then, through electroplating with a plating line or a via filling line, the surface of the upper conductive layer 3 is electroplated with a surface electroplating layer 6. If the lower surface of the lower conductive layer 1 does not have an insulating layer, it will also be electroplated with a layer of metal. If the lower surface of the lower conductive layer 1 is still an insulating material, it will not be electroplated.

[0047] After electroplating of blind via 4a, a conductive post 4b is formed within the hole. This post 4b physically and electrically connects lower conductive layer 1 to upper conductive layer 3. Furthermore, there are intergranular interfaces between post 4b and lower conductive layer 1, and between post 4b and upper conductive layer 3. These interfaces are the interface between the electroplated layer and the original conductive layer, and are the weakest points in blind via reliability. The intergranular interface 5 between post 4b and lower conductive layer 1 presents the greatest risk of failure in blind via 4a. The crystal interface 5 itself is the interface between the electroplating layer and the original conductive layer. There will be many lattice defects, various natural stresses, and a high probability of containing impurities. For example, the carbon content is too high, and there is an alloy of metal and carbon (for example, when the materials of the electroplating layer and the original conductive layer are both copper, the alloy of metal and carbon is a copper-carbon alloy), or even worse, there are carbon-containing organic matter, such as residual glue, residual PI polyimide and other organic matter. In short, once there are too many inorganic impurities, due to environmental influences or time reasons, the lower conductive layer 1 and the connecting hole conductive column 4b are disconnected at the crystal interface 5, which will cause systemic failure and heavy losses; once organic matter exists, there is a direct blind hole risk, which causes the connecting hole conductive column 4b to fail in electrical connection between the upper conductive layer 1 and the lower conductive layer 3.

[0048] like Figure 2As shown, the present invention uses a laser beam 7 to shoot at the blind hole 4a in the surface electroplating layer 6, directly generating a thermal field 8. The heat of the thermal field 8 is transmitted toward the connecting hole conductive column 4b and the corresponding lower conductive layer 1, forming a strong temperature gradient. Not only that, a temperature gradient is also generated between the conductive area of the circuit board (including the upper conductive layer 3, the connecting hole conductive column 4b and the lower conductive layer 1) and the intermediate insulating layer 2. In this way, as the temperature rises, the thermal expansion coefficient is also different. Generally, the thermal expansion coefficient of non-metal is greater than that of metal. The connecting hole conductive column 4b and the lower conductive layer 1 will generate a huge thermal stress field at the crystal interface 5, which includes not only shear force but also tensile stress. At this time, there are the following situations: 1) When the conductive column 4b of the connecting hole is connected to the lower conductive layer 1 without impurities (lattice defect stress, etc. are not ruled out), the heat of the conductive column 4b of the connecting hole will be smoothly introduced into the lower conductive layer 1, the temperature gradient between the conductive column 4b of the connecting hole and the lower conductive layer 1 is small, and the thermal stress (mainly manifested as tensile stress) of the crystal interface 5 connecting the conductive column 4b of the connecting hole and the lower conductive layer 1 is small, and the connection surface is likely to remain normal. 2) When there are impurities or voids in the crystal interface 5 where the connecting hole conductive pillar 4b connects to the lower conductive layer 1, the heat of the connecting hole conductive pillar 4b will be delayed in being introduced into the lower conductive layer 1, the temperature gradient between the connecting hole conductive pillar 4b and the lower conductive layer 1 is large, and the crystal interface 5 where the connecting hole conductive pillar 4b connects to the lower conductive layer 1 generates a large thermal stress (mainly shear stress); in addition, since the conductive layer (including the lower conductive layer 1 and the upper conductive layer 3) and the intermediate insulating layer 2 also have a temperature gradient, the intermediate insulating layer 2 also expands due to heat and is squeezed by the lower conductive layer 1 and the upper conductive layer 3, the intermediate insulating layer 2 will be subjected to compressive stress, the lower conductive layer 1 and the upper conductive layer 3 are physically connected by the connecting hole conductive pillar 4b, and the lower conductive layer 1 and the upper conductive layer 3 are subjected to tensile stress from the connecting hole conductive pillar 4b. Ultimately, this tensile stress will act on both ends of the connecting hole conductive pillar 4b, including the crystal interface 5. When the temperature gradient is large enough, the crystal interface 5 will produce microcracks or break under the combined action of stresses such as shear force and tensile stress. 3) When there is organic matter, such as residual glue, at the crystal interface 5 where the conductive column 4b of the connecting hole is connected to the lower conductive layer 1, the residual glue has very poor thermal conductivity and expands when heated, directly "exploding" the conductive column 4b of the connecting hole and the lower conductive layer 1, resulting in mechanical connection failure and electrical connection failure. In this case, the expansion of the intermediate insulating layer 2 around the conductive column 4b of the connecting hole and the lower conductive layer 1 generates tensile stress, the shear force generated by the inconsistent thermal expansion of the conductive column 4b of the connecting hole and the lower conductive layer 1, and the "explosion" pressure generated by the violent expansion of the organic matter between the conductive column 4b of the connecting hole and the lower conductive layer 1 due to heat, this situation will first lead to electrical connection failure.

[0049] Thermal energy transfers from high to low temperatures, and the spatial variation between high and low temperatures is called a temperature gradient. The temperature gradient of the present invention involves continuous laser heating to maintain a local constant temperature on the circuit board (heat from the heated area is constantly dissipated, supplemented by heat input from the laser heating, thereby maintaining a local constant temperature).

[0050] After laser heating the blind hole using the laser beam 7 to apply a thermal field, the blind hole is then subjected to electrical testing, mechanical testing, or metallographic testing.

[0051] Specifically, electrical testing of the blind via involves conducting online or post-offline electrical testing on both ends of the conductive pillar 4b when the conductive pillar 4b is connected to the lower conductive layer 1 without impurities. The electrical performance of the connection between the lower conductive layer 1 and the upper conductive layer 3 via the conductive pillar 4b remains unchanged. If impurities or voids are present at the interface 5 where the conductive pillar 4b connects the lower conductive layer 1, causing microcracks or even fractures due to excessive thermal stress, the electrical performance of the connection between the lower conductive layer 1 and the upper conductive layer 3 via the conductive pillar 4b will deteriorate. The electrical testing refers to electrical testing of capacitance, resistance, inductance, voltage, current, and other aspects; the electrical performance refers to electrical parameters such as capacitance, resistance, and inductance.

[0052] In addition, electrical testing methods include four-wire testing and two-wire testing. Circuit board testing is an indispensable part of electronic production, of which four-wire testing and two-wire testing are two commonly used testing methods.

[0053] Four-wire testing involves injecting a test signal into two of the four pins on a PCB, while the other two pins receive the return signal. This testing method can measure all electrical performance parameters, including continuity, insulation, capacitance, and inductance. Specifically, four-wire testing verifies the proper function of a PCB by adding four wires to the board: VCC, GND, signal output, and signal input. These four wires connect to the VCC, GND, signal, and input lines on the board, respectively, to perform a systematic test of the board and ensure its proper function. Four-wire testing of PCBs is based on resistance measurement. During the test, the test equipment injects current into the signal output line and measures the voltage between this line and the input line. This method calculates the signal input and output resistance, as well as the signal output offset voltage and AC coupling. Based on these parameters, it is possible to determine whether the PCB's output and input meet design requirements and, therefore, verify its proper function.

[0054] The two-wire test only tests the resistance value between two pins, and the test is achieved by placing a resistor between the test pins. This method can only test basic parameters such as conductivity and resistance value, and cannot test other electrical parameters.

[0055] The mechanical testing of the blind vias specifically involves mechanically testing the connection between the conductive pillar 4b and the crystal interface 5 of the lower conductive layer 1. A copper tensile test is performed on the conductive pillar 4b to ensure that the mechanical properties of the connection have not deteriorated. If the tensile test causes the connection to break, the product is deemed unqualified.

[0056] The metallographic test of the blind hole is specifically as follows: metallographic mechanical sectioning is performed on the hole copper, and the crystal interface 5 connecting the conductive column 4b of the connecting hole and the upper conductive layer 3 and / or the lower conductive layer 1 is observed under a microscope. If there is no breakage or microcracks, it means that the hole copper connection is good, otherwise it is judged to be poor.

[0057] The current blind hole reliability temperature cycle shock test of circuit boards in the industry has the following disadvantages: 1) Energy consumption. The temperature cycle test heats the internal temperature of the entire test cabinet, which increases the overall temperature of the circuit board. 2) Inefficiency. The temperature cycle shock test requires the overall temperature of the circuit board to increase, while the insulation material is a poor conductor of heat and heats up slowly. 3) It can only be tested offline, and it is a destructive sampling test, which cannot achieve online full inspection. 4) The maximum temperature cannot exceed the temperature that the insulation material can withstand. Therefore, the maximum temperature is generally 245 degrees, and cannot exceed 260 degrees at most. This maximum temperature is limited by the maximum temperature that the insulation material can withstand.

[0058] The advantages of the present invention are: 1) energy saving, the present invention uses a laser beam to directly irradiate the conductive column of the connection hole, which is the weakest part that needs to be tested in the temperature cycle, directly forming a local thermal field with a large temperature gradient, and can achieve the test goal with minimal energy input; 2) high efficiency, the laser beam heating speed is extremely fast, and a local thermal field with a huge temperature gradient is formed in the shortest time; 3) can realize online testing, the laser beam can efficiently perform local heating testing, and those that pass the heating test (equivalent to the aging test) can proceed to the next process, and those that fail will be directly scrapped; 4) can realize local high temperature testing, the laser beam can locally heat the conductive material to an extremely high temperature (for example This is the case with laser cutting of circuit boards. The cutting temperature is very high, which can vaporize the copper layer, but does not affect the bonding strength between the insulating material of the circuit board and the copper layer. A large temperature gradient is obtained, which not only introduces the traditional tensile test factor, but also introduces the shear force test factor of the crystal interface, which can achieve more rigorous testing; 5) The traditional circuit board temperature shock cycle test is a relatively balanced temperature test inside the circuit board, that is, the temperature gradient inside the circuit board is small. The invention can realize both small temperature gradient testing (controlling the speed and size of the laser beam heating energy input) and large temperature gradient testing (the laser beam violently heats the corresponding part of the conductive column of the connecting hole).

[0059] The method of the present invention also has the following preferred embodiment:

[0060] Preferably, in the step 1, before irradiating the laser beam to the circuit board, the method further includes: placing the circuit board on a heat sink.

[0061] Specifically, a heat sink is an object that can quickly conduct heat away. It allows the circuit board attached to it to dissipate heat naturally and passively, or actively and temperature-controlled. This approach, by adding a heat sink, allows for faster heat conduction away from the laser heating point, exacerbating the thermal field temperature gradient and further improving detection effectiveness and requirements.

[0062] Preferably, in the step 1, irradiating the laser beam to the circuit board specifically comprises: irradiating the laser beam to the upper conductive layer and / or the lower conductive layer of the circuit board;

[0063] When the laser beam is directed toward the upper conductive layer of the circuit board, the thermal field is specifically an upper thermal field, and the direction of the temperature gradient of the upper thermal field is from the upper conductive layer to the lower conductive layer;

[0064] When the laser beam is directed toward the lower conductive layer of the circuit board, the thermal field is specifically a lower thermal field, and the direction of the temperature gradient of the lower thermal field is from the lower conductive layer to the upper conductive layer;

[0065] When the laser beam is directed toward the upper conductive layer and the lower conductive layer of the circuit board, the thermal field includes an upper thermal field and a lower thermal field. The direction of the temperature gradient of the upper thermal field is from the upper conductive layer to the lower conductive layer, and the direction of the temperature gradient of the lower thermal field is from the lower conductive layer to the upper conductive layer.

[0066] Specifically, the laser beam can be emitted toward the upper conductive layer, with the direction of the thermal field temperature gradient directed from the upper conductive layer to the lower conductive layer; or it can be emitted toward the lower conductive layer, with the direction of the thermal field temperature gradient directed from the lower conductive layer to the upper conductive layer; or the laser beam can be emitted simultaneously or sequentially toward the upper conductive layer and the lower conductive layer (when the laser beam is emitted simultaneously toward the upper conductive layer and the lower conductive layer, two laser beams are provided, one directed toward the upper conductive layer and the other toward the lower conductive layer). It is preferred that the heating point of the laser beam on the conductive material be closest to the crystal interface between the conductive pillar of the connecting hole and the lower conductive layer, so that a temperature gradient can be formed at the crystal interface 5 at the fastest speed.

[0067] For example: Figure 2As shown, the upper conductive layer 3 is 9 micron thick copper, the lower conductive layer 1 is 30 micron thick copper foil, and there may be other layers of circuit boards under the lower conductive layer 1 (not shown in the figure), the middle insulating layer 2 is a 75 micron thick circuit board high-speed insulating material, the blind hole 4a has an upper aperture of 150 microns and a lower aperture of 120 microns. After chemical copper deposition and hole-filling electroplating processes, the connecting hole conductive column 4b fills the blind hole 4a, and the surface electroplating layer 6 has a thickness of 10 microns. The biggest risk point for the reliability of the blind hole lies in the bonding strength between the connecting hole conductive column 4b and the crystal interface 5 of the lower conductive layer 1. This embodiment uses a 50 watt @ 100KHz green laser to output a laser beam 7 with a pulse width of 30 nanoseconds. The heating spot of the laser beam 7 adopts a circular flat-top design with a spot size of 60 microns. The heating time is set from 500 microseconds to 10 milliseconds. The laser beam 7 performs laser heating on the blind hole opening of the upper conductive layer 3. The blind hole is then sliced, as shown in FIG. Figure 5 As shown, if there is no crack, breakage or gap at the crystal interface 5, it indicates that the blind hole is reliable; if there is Figure 4 As shown, there are gaps or cracks in the crystal interface 5, such as the gap 9 at the bottom of the blind hole (for the convenience of expression, the gap 9 is marked at the bottom of another blind hole). Then the temperature shock of the blind hole will not pass through, and the blind hole determination is unreliable. The specific reasons will be analyzed in other processes.

[0068] Another example: Figure 3 As shown, the upper conductive layer 3 is a 12-micron thick copper surface, the lower conductive layer 1 is a 12-micron thick copper foil, and there is a circuit board with other layer structures under the lower conductive layer 1 (not shown in the figure). The middle insulating layer 2 is a 25-micron thick PI polyimide insulating material. The upper aperture of the blind hole 4a is 100 microns and the lower aperture is 80 microns. After the black hole and electroplating processes, the surface electroplating layer 6 is 10 microns thick. The connecting hole conductive column 4b passes through the blind hole 4a to connect the lower conductive layer 1 and the upper conductive layer 3. The biggest risk point of the blind hole reliability is still the bonding force between the conductive column 4b of the connecting hole and the crystal interface 5 of the lower conductive layer 1. This embodiment uses a 30 watt @ 100KHz infrared laser to output a laser beam 7 with a pulse width of 120 nanoseconds. The laser beam 7 heating spot adopts a circular flat top design with a spot size of 60 microns and a heating time setting of 500 microseconds to 10 milliseconds. Since the lower conductive layer 1 is closer to the crystal interface 5, the laser beam 7 performs laser heating on the bottom of the blind hole of the lower conductive layer 1 (the lower conductive layer will also be electroplated with 10 microns of copper in the figure, which is not marked in the figure). Then the blind hole is sliced, as shown in FIG. Figure 7 As shown, if there is no crack, breakage or gap at the crystal interface 5, it indicates that the blind hole is reliable; if there is Figure 6 If a gap appears at the crystal interface 5, such as the gap 9 at the bottom of the blind hole (for the sake of convenience, the gap 9 is marked at the bottom of another blind hole), then the temperature shock test of the blind hole will fail, and the blind hole determination will be unreliable. The specific reason will be analyzed in other processes.

[0069] In other embodiments, the laser beam 7 performs laser heating on the blind hole opening of the upper conductive layer 3 and the laser beam 7 performs laser heating on the blind hole bottom of the lower conductive layer 1, i.e., double-sided laser heating, which can further improve the heating efficiency.

[0070] Preferably, in the step 1, performing laser heating on the blind hole to apply a thermal field is specifically: in the time dimension, performing laser intermittent or cyclic heating on the blind hole to apply a thermal field.

[0071] Specifically, intermittent or cyclic laser heating is performed on the blind hole to apply a thermal field, so as to achieve high and low temperature cycle aging test of the blind hole reliability.

[0072] Preferably, in step one, performing laser heating on the blind hole to apply a thermal field is specifically: in the spatial dimension, performing laser fixed-point impact heating or / and scanning motion heating on the blind hole to apply a thermal field.

[0073] Specifically, the laser beam can be used for fixed-point heating. If the heating surface needs to be relatively large, a laser beam scanning method can be used for heating.

[0074] Preferably, in step one, performing laser heating on the blind hole to apply a thermal field specifically includes: performing laser heating on a single blind hole to apply a thermal field, or performing laser heating on a plurality of blind holes simultaneously or successively to apply a thermal field.

[0075] Preferably, when laser heating is performed simultaneously or sequentially on a plurality of blind holes to apply a thermal field, in step 2, the electrical test on the blind holes is specifically performed by performing electrical series and / or parallel electrical tests on the plurality of blind holes.

[0076] Preferably, in the step 2, performing electrical testing on the blind vias specifically includes: performing online electrical testing or offline electrical testing on the blind vias.

[0077] Specifically, online testing involves using test equipment as part of a PCB production line to perform random or full inspections of the reliability of blind vias on PCBs. Offline testing involves testing not on the PCB production line but by taking individual samples to a physical laboratory for testing.

[0078] Preferably, in step 2, the electrical testing of the blind hole is specifically performed by: performing the electrical testing on the blind hole after performing laser heating to apply a thermal field, or performing the electrical testing on the blind hole while performing laser heating to apply a thermal field.

[0079] Preferably, the laser beam is a composite laser beam.

[0080] Specifically, the composite laser beam can be a combination of laser beams with different wavelengths, or different pulse widths, or different laser powers, or different laser pulse repetition frequencies, or different beam divergence angles, or different beam transverse field intensity distributions, and finally a combined laser beam is formed to perform metal heat treatment on the conductive copper pillars of the circuit board.

[0081] Among them, the laser beam wavelength includes far infrared, infrared, visible light, ultraviolet, and deep ultraviolet laser wavelengths; and / or the laser beam pulse width includes continuous laser, millisecond, microsecond, nanosecond, picosecond, femtosecond and other pulse widths.

[0082] In addition, any laser light source can be used in the present invention, including gas lasers, solid lasers; semiconductor lasers, carbon dioxide lasers, fiber lasers, semiconductor-pumped solid lasers; continuous wave lasers, pulsed lasers, quasi-continuous wave lasers; Q-switched lasers, mode-locked ultrafast lasers, seed-amplified continuous and pulsed lasers, etc.

[0083] Preferably, the field intensity distribution of the projection spot of the heat field applied by the laser beam is specifically one of Gaussian distribution, flat-top Gaussian distribution, flat-top distribution, annular distribution, polygonal field intensity distribution, or any combination thereof.

[0084] Specifically, the laser beam heating spot depends on the specific situation and can be designed specifically to optimize the thermal stress field at the interface between the conductive pillar in the connection hole and the upper conductive layer and / or the lower conductive layer. The so-called optimal refers to the one that can generate the maximum destructive stress.

[0085] Preferably, the upper conductive layer is formed by electroplating together with the connecting hole conductive pillars in the blind hole.

[0086] Specifically, for chip carrier circuit boards, the additive method is generally used at present. That is, a lower conductive layer and an insulating layer are first formed, and then after laser drilling of blind holes, an additive method is used to form an electroplating seed layer by chemical copper deposition or ion sputtering injection, and then electroplating is used to thicken it to form connecting hole conductive columns and an upper conductive layer.

[0087] Preferably, the blind vias include any one or any combination of single-stage blind vias, multi-stage blind vias, stacked vias and cross-layer blind vias.

[0088] Specifically, a single-stage blind hole such as Figure 2 or Figure 3 The blind hole shown in .

[0089] like Figure 8As shown, the second intermediate insulating layer 21 is adhered to the lower conductive layer 1, and the third conductive layer 11 is adhered to the second intermediate insulating layer 21. The blind hole 4a passes through the upper conductive layer 3, the intermediate insulating layer 2, the lower conductive layer 1, and the second intermediate insulating layer 21. The bottom of the blind hole is on the upper surface of the third conductive layer 11. The crystal interface 5 is the connection surface between the conductive column 5 of the connecting hole and the third conductive layer 11. This is a second-order blind hole; the same applies to multi-order blind holes above the second order.

[0090] like Figure 9 The figure shows a stacked structure consisting of multiple first-order blind vias. The lower conductive layer 1 is bonded to the second intermediate insulating layer 21, which is then bonded to the third conductive layer 11. The third conductive layer 11 is bonded to the third intermediate insulating layer 22, which is then bonded to the fourth conductive layer 111.

[0091] like Figure 10 If the conductive pillar 4b of the connection hole is disconnected from the lower conductive layer 1, and the two are insulated by the cross-layer insulating layer 12, this type of hole is a cross-layer hole.

[0092] Preferably, the conductive metal material of the upper conductive layer, the conductive pillars of the connection holes and the lower conductive layer includes any one of copper, iron, gold, nickel, chromium and titanium, or a combination of any multiple materials;

[0093] or / and,

[0094] The insulating material of the intermediate insulating layer includes any one of silicon, ceramic, glass, and polymer insulating material, or a combination of any multiple materials.

[0095] Example 2:

[0096] The present invention provides a blind hole reliability testing device for performing reliability testing on blind holes on a circuit board, wherein the circuit board comprises at least a stacked lower conductive layer, an intermediate insulating layer, and an upper conductive layer; a connecting hole conductive column is provided in the blind hole, the connecting hole conductive column penetrates the intermediate insulating layer, and is connected to the upper conductive layer at the hole mouth of the blind hole and to the lower conductive layer at the hole bottom of the blind hole;

[0097] The blind hole reliability testing equipment comprises:

[0098] A motion platform, which is used to carry the circuit board and drive the circuit board to move;

[0099] A positioning module, used to locate the circuit board on the motion platform and obtain positioning information;

[0100] a laser for generating a laser beam;

[0101] a galvanometer scanning and flat-field focusing device, connected to the laser and the positioning module, for performing galvanometer scanning and flat-field focusing on the laser beam and outputting the laser beam, and directing the output laser beam toward the circuit board according to the positioning information, and performing laser heating on the blind hole to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive pillar of the connection hole, and the lower conductive layer, and simultaneously forming a temperature gradient between the conductive area of the circuit board and the intermediate insulating layer surrounding the blind hole;

[0102] The temperature gradient and temperature level of the thermal field are controlled by controlling the heating speed and intensity of the laser beam; the thermal field temperature of the connecting hole conductive pillar is lower than the melting temperature of the connecting hole conductive pillar; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive pillar and the upper conductive layer and the lower conductive layer;

[0103] A testing module is used to perform electrical testing, mechanical testing, or metallographic testing on the blind via to determine the reliability of the electrical connection between the conductive column in the connection hole and the lower conductive layer and / or the upper conductive layer.

[0104] Example 3:

[0105] The present invention provides a blind hole reliability testing device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the computer program implements the blind hole reliability testing method described above when executed.

[0106] Example 4:

[0107] The present invention provides a blind hole reliability testing system, comprising a machine platform, a laser, and the blind hole reliability testing device as described above, wherein the blind hole reliability testing device is electrically connected to the laser;

[0108] The machine is used to carry the circuit board to be processed;

[0109] The laser is used to generate a laser beam;

[0110] The blind hole reliability testing device is used to control the laser beam generated by the laser to be directed toward the circuit board, and to perform laser heating on the blind hole on the circuit board to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive pillar of the connection hole, and the lower conductive layer, and at the same time forming a temperature gradient between the conductive area of the circuit board and the intermediate insulating layer surrounding the blind hole;

[0111] The temperature gradient and temperature level of the thermal field are controlled by controlling the heating speed and intensity of the laser beam; the thermal field temperature of the connecting hole conductive pillar is lower than the melting temperature of the connecting hole conductive pillar; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive pillar and the upper conductive layer and the lower conductive layer;

[0112] The blind vias are subjected to electrical testing, mechanical testing, or metallographic testing to determine the reliability of the electrical connection between the conductive pillars in the connection holes and the lower conductive layer and / or the upper conductive layer.

[0113] The blind via reliability testing method, equipment, device, and system provided by the present invention have the following advantages over the prior art:

[0114] 1) Higher detection capability: The present invention uses a laser beam to heat near the key points of blind hole reliability detection, forming a thermal field with a large temperature gradient. This thermal field brings tensile stress and shear stress to the crystal interface at the bottom of the blind hole, and the impact strength of the blind hole bottom detection is much higher than the detection impact strength of conventional temperature cycle detection. Due to the existence of the temperature gradient, the heating of the electroplated copper in the blind hole can be much higher than the withstand temperature of the insulating material. Such a large temperature gradient is more likely to cause damage to the defects at the bottom of the blind hole. Therefore, the present invention can achieve higher blind hole reliability detection standards.

[0115] 2) More flexible testing: The present invention can perform blind hole reliability testing offline or in a circuit board production line.

[0116] 3) Detection efficiency is greatly improved. Due to the flexibility of laser heating and the extremely fast temperature rise of laser heating, the timeliness of blind hole reliability detection on circuit boards is improved by orders of magnitude.

[0117] 4) Full inspection of blind vias is possible. Conventional temperature cycling shock tests are destructive and are sample sampling tests, which then evaluate production line parameters. Due to the high efficiency of the detection method, the present invention can achieve full inspection of blind vias on production line circuit boards, eliminating unqualified products and retaining qualified products (laser heating is local heating and does not affect the reliability of qualified products).

[0118] 5) Energy saving and environmental protection The method of the present invention is to perform local laser heating on a very limited part of the blind hole, which is a very small part of the circuit board. Therefore, the energy consumption of the equipment is very small, which is much more energy-saving than temperature cycle impact box heating (not only the box is heated, but the entire circuit board must be heated).

[0119] The reader should understand that in the description of this specification, reference to the terms "one embodiment", "some embodiments", "examples", "specific examples" or "some examples" 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 invention. 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 can be combined in any one or more embodiments or examples in a suitable manner. In addition, different embodiments or examples described in this specification and features of different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0120] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A blind hole reliability testing method, characterized in that: Reliability testing is performed on blind vias on a circuit board, the circuit board comprising at least a stacked lower conductive layer, an intermediate insulating layer, and an upper conductive layer; a connecting hole conductive post is provided in the blind via, the connecting hole conductive post penetrates the intermediate insulating layer, and connects to the upper conductive layer at the opening of the blind via and to the lower conductive layer at the bottom of the blind via; The blind hole reliability testing method comprises: Step 1: Directing a laser beam toward the circuit board and aiming at the blind hole for laser heating to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive pillar of the connection hole, and the lower conductive layer, and simultaneously forming a temperature gradient between the conductive area of the circuit board and the intermediate insulating layer surrounding the blind hole; The temperature gradient and temperature level of the thermal field are controlled by controlling the heating speed and intensity of the laser beam; the thermal field temperature of the connecting hole conductive pillar is lower than the melting temperature of the connecting hole conductive pillar; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive pillar and the upper conductive layer and the lower conductive layer; Step 2: performing electrical testing, mechanical testing, or metallographic testing on the blind via to determine the reliability of the electrical connection between the conductive pillar in the connection hole and the lower conductive layer and / or the upper conductive layer.

2. The blind hole reliability testing method according to claim 1, characterized in that: In the step 1, before irradiating the laser beam to the circuit board, the method further includes: placing the circuit board on a heat sink.

3. The blind hole reliability testing method according to claim 1, characterized in that: In the step 1, irradiating the laser beam to the circuit board specifically comprises: irradiating the laser beam to the upper conductive layer and / or the lower conductive layer of the circuit board; When the laser beam is directed toward the upper conductive layer of the circuit board, the thermal field is specifically an upper thermal field, and the direction of the temperature gradient of the upper thermal field is from the upper conductive layer to the lower conductive layer; When the laser beam is directed toward the lower conductive layer of the circuit board, the thermal field is specifically a lower thermal field, and the direction of the temperature gradient of the lower thermal field is from the lower conductive layer to the upper conductive layer; When the laser beam is directed toward the upper conductive layer and the lower conductive layer of the circuit board, the thermal field includes an upper thermal field and a lower thermal field. The direction of the temperature gradient of the upper thermal field is from the upper conductive layer to the lower conductive layer, and the direction of the temperature gradient of the lower thermal field is from the lower conductive layer to the upper conductive layer.

4. The blind hole reliability testing method according to claim 1, characterized in that: In the step 1, performing laser heating on the blind hole to apply a thermal field specifically includes: performing intermittent or cyclic laser heating on the blind hole to apply a thermal field in the time dimension.

5. The blind hole reliability testing method according to claim 1, characterized in that: In the step 1, performing laser heating on the blind hole to apply a thermal field is specifically: in the spatial dimension, performing laser fixed-point impact heating or / and scanning motion heating on the blind hole to apply a thermal field.

6. The blind hole reliability testing method according to claim 1, characterized in that: In the step 1, performing laser heating on the blind hole to apply a thermal field specifically includes: performing laser heating on a single blind hole to apply a thermal field, or performing laser heating on a plurality of blind holes simultaneously or sequentially to apply a thermal field.

7. The blind hole reliability testing method according to claim 6, characterized in that: When laser heating is performed simultaneously or sequentially on a plurality of blind holes to apply a thermal field, in step 2, the electrical test on the blind holes specifically includes: performing an electrical test on the plurality of blind holes in series or / and in parallel.

8. The blind via reliability testing method according to claim 1, wherein: In the step 2, performing electrical testing on the blind vias specifically includes: performing online electrical testing or offline electrical testing on the blind vias.

9. The blind hole reliability testing method according to claim 1, characterized in that: In the step 2, the electrical test on the blind hole is specifically performed by: performing the electrical test on the blind hole after performing laser heating to apply a thermal field, or performing the electrical test on the blind hole while performing laser heating to apply a thermal field.

10. The blind via reliability testing method according to claim 1, wherein: The laser beam is a composite laser beam.

11. The blind via reliability testing method according to claim 1, wherein: The field intensity distribution of the projection spot of the laser beam is specifically one of Gaussian distribution, flat-top Gaussian distribution, flat-top distribution, annular distribution, polygonal field intensity distribution, or any combination thereof.

12. The blind via reliability testing method according to claim 1, wherein: The upper conductive layer is formed by electroplating together with the connecting hole conductive pillars in the blind hole.

13. The blind via reliability testing method according to claim 1, wherein: The blind vias include any one of single-stage blind vias, multi-stage blind vias, stacked vias and cross-layer blind vias, or any combination of multiple thereof.

14. The blind via reliability testing method according to claim 1, wherein: The conductive metal material of the upper conductive layer, the conductive pillars of the connection holes and the lower conductive layer includes any one of copper, iron, gold, nickel, chromium and titanium or a combination of any multiple materials; or / and, The insulating material of the intermediate insulating layer includes any one of silicon, ceramic, glass, and polymer insulating material, or a combination of any multiple materials.

15. A blind hole reliability testing device, characterized in that: Used to perform reliability testing on blind vias on a circuit board, the circuit board comprising at least a stacked lower conductive layer, an intermediate insulating layer, and an upper conductive layer; a connecting hole conductive post is provided in the blind via, the connecting hole conductive post passes through the intermediate insulating layer, and is connected to the upper conductive layer at the opening of the blind via and to the lower conductive layer at the bottom of the blind via; The blind hole reliability testing equipment comprises: A motion platform, which is used to carry the circuit board and drive the circuit board to move; A positioning module, used to locate the circuit board on the motion platform and obtain positioning information; a laser for generating a laser beam; a galvanometer scanning and flat-field focusing device, connected to the laser and the positioning module, for performing galvanometer scanning and flat-field focusing on the laser beam and outputting the laser beam, and directing the output laser beam toward the circuit board according to the positioning information, and performing laser heating on the blind hole to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive pillar of the connection hole, and the lower conductive layer, and simultaneously forming a temperature gradient between the conductive area of the circuit board and the intermediate insulating layer surrounding the blind hole; The temperature gradient and temperature level of the thermal field are controlled by controlling the heating speed and intensity of the laser beam; the thermal field temperature of the connecting hole conductive pillar is lower than the melting temperature of the connecting hole conductive pillar; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive pillar and the upper conductive layer and the lower conductive layer; A testing module is used to perform electrical testing, mechanical testing, or metallographic testing on the blind via to determine the reliability of the electrical connection between the conductive column in the connection hole and the lower conductive layer and / or the upper conductive layer.

16. A blind hole reliability testing device, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the computer program implements the blind hole reliability testing method according to any one of claims 1 to 14 when executed.

17. A blind hole reliability testing system, characterized in that: It comprises a machine, a laser and the blind hole reliability testing device according to claim 16, wherein the blind hole reliability testing device is electrically connected to the laser; The machine is used to carry the circuit board to be processed; The laser is used to generate a laser beam; The blind hole reliability testing device is used to control the laser beam generated by the laser to be directed toward the circuit board, and to perform laser heating on the blind hole on the circuit board to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive pillar of the connection hole, and the lower conductive layer, and at the same time forming a temperature gradient between the conductive area of the circuit board and the intermediate insulating layer surrounding the blind hole; The temperature gradient and temperature level of the thermal field are controlled by controlling the heating speed and intensity of the laser beam; the thermal field temperature of the connecting hole conductive pillar is lower than the melting temperature of the connecting hole conductive pillar; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive pillar and the upper conductive layer and the lower conductive layer; The blind vias are subjected to electrical testing, mechanical testing, or metallographic testing to determine the reliability of the electrical connection between the conductive pillars in the connection holes and the lower conductive layer and / or the upper conductive layer.

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