Blind hole reliability test method, equipment, device and system

Abstract

The invention relates to a blind hole reliability test method, equipment, device and system, and the method comprises the steps: enabling a laser beam to irradiate a circuit board, and carrying out the laser heating of a blind hole, so as to apply a thermal field, and forming a temperature gradient; and performing an electrical test, a mechanical test or a metallographic test on the blind holes to judge the reliability of the electrical connection between the conductive columns of the connecting holes and the lower conductive layer or / and the upper conductive layer. According to the invention, through local high-temperature heating of laser beams, mechanical and electronic connection of electroplated metal and native metal at the bottom of the blind hole, an energy-saving, efficient and online blind hole reliability detection test is carried out, the global industry blank is filled up, and the industry is no longer afraid of the blind hole of the circuit board; meanwhile, according to the principle of the invention, due to the existence of the temperature gradient, the local heating temperature of the electroplated metal in the blind hole can be far higher than the temperature which can be borne by the insulating material of the middle insulating layer, the test strict degree is far higher than that of a temperature circulation box body test in the current industry, and a more reliable detection result is obtained.

Description

Technical Field

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

[0002] Blind vias have been a topic of great fear in the circuit board industry for decades. The key is that it is difficult to control the residual glue and copper-carbon alloy at the bottom of the hole with the existing blind via production methods. Once discovered, a large number of products will be scrapped, resulting in heavy losses. The existing blind via control is all experience-based control and sampling inspection, which is very cautious, and the sampling inspection is a destructive inspection. The current sampling inspection in the industry is mainly temperature cycle shock testing. Other AOI full inspections in the production process only check whether there is residual glue at the bottom of the hole, and do not check the alloy of metal and carbon at the bottom of the blind hole (such as copper-carbon alloy); the four-wire test after electroplating only checks whether there is residual glue at the bottom of the hole. If it is just copper-carbon alloy, the conductivity does not change much, so the four-wire inspection cannot detect the problem, but the presence of copper-carbon alloy at the bottom of the blind hole itself is a fatal problem.

[0003] In the current circuit board industry, whether it is a soft board, a hard board, a hard-soft board, a carrier board, a high-frequency high-speed board, an AI board, an automotive board, etc., once the circuit board blind hole is involved, there is a blind hole reliability test. The current blind hole reliability test generally adopts the temperature cycle shock test. Some use the cycle from sub-zero low temperature to above zero high temperature, and some use 50 degrees Celsius to 245 degrees Celsius or even 260 degrees Celsius for temperature cycle shock. In order to balance the temperature rise and fall of the entire circuit board, the temperature shock cycle speed is very slow. Generally, one temperature cycle per hour is considered relatively fast. In this way, 30 temperature cycles will take a lot of time. Moreover, this type of test cannot be done online on the circuit board production line, but is taken to the physical laboratory for separate sampling and offline sampling test, and it is even more impossible to achieve a full inspection of blind hole reliability. The industry urgently needs to find a way to detect and fully inspect blind holes with residual glue or copper-carbon alloy at the bottom of the blind hole to completely avoid blind hole 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 hole reliability test method, which performs a reliability test on a blind hole on a circuit board, wherein the circuit board at least comprises 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 is connected to the lower conductive layer at the hole bottom of the blind hole;

[0007] The blind hole reliability testing method comprises:

[0008] Step 1: directing a laser beam toward the circuit board and aligning the blind hole for laser heating to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive column of the connecting 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 around 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 column is lower than the melting temperature of the connecting hole conductive column; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive column and the upper conductive layer and the lower conductive layer;

[0010] Step 2: 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 and / or the upper conductive layer.

[0011] In a second aspect, the present invention provides a blind hole reliability test device, which is used to perform reliability test on a blind hole on a circuit board, wherein the circuit board at least comprises 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 is connected to the lower conductive layer at the hole 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 emitting the output laser beam to 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 column of the connecting hole and the lower conductive layer, and forming a temperature gradient between the conductive area of ​​the circuit board and the intermediate insulating layer around 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 column is lower than the melting temperature of the connecting hole conductive column; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive column 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 hole to determine the reliability of the electrical connection between the conductive column of 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 platform 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 to 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 connecting hole conductive column 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 around 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 column is lower than the melting temperature of the connecting hole conductive column; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive column and the upper conductive layer and the lower conductive layer;

[0025] The blind hole is subjected to electrical testing, mechanical testing or metallographic testing to determine the reliability of the electrical connection between the conductive column of the connection hole 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 test method, equipment, device and system of the present invention performs energy-saving, high-efficiency and full-online blind hole reliability test on the mechanical and electronic connection between the electroplated metal at the bottom of the blind hole and the original metal through local high-temperature heating with a laser beam, filling the 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 principle of the present invention, due to the existence of 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 middle insulating layer can withstand, and the strictness of the test is much higher than the current industry's temperature cycle box test, with more reliable test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 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 hole on a circuit board;

[0029] Figure 3 Another example diagram for implementing a reliability test on a blind hole 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 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 schematic diagram;

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

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

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

[0037] In the accompanying drawings, the components represented by the reference numerals are listed 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 in conjunction with 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] Embodiment 1:

[0041] A blind hole reliability test method is provided, wherein the blind hole on a circuit board is subjected to a reliability test, wherein the circuit board at least comprises a stacked lower conductive layer, an intermediate insulating layer and an upper conductive layer, and the bottom of the blind hole is the lower 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 opening of the blind hole, and is connected to the lower conductive layer at the bottom of the blind hole;

[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 aligning the blind hole for laser heating to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive column of the connecting 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 around 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 column is lower than the melting temperature of the connecting hole conductive column; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive column and the upper conductive layer and the lower conductive layer;

[0045] Step 2: 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 and / or the upper conductive layer.

[0046] Specifically, 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, and a blind hole 4a is processed on the upper conductive layer 3, the blind hole 4a passes through the intermediate insulating layer 2, and the bottom of the hole is the surface of the lower conductive layer 1. After the circuit board is black hole or black shadow or chemical copper deposition, the lower conductive layer 1 and the upper conductive layer 3 have conductive properties, so that after electroplating by electroplating line or hole filling line, the surface of the upper conductive layer 3 will be electroplated with a surface electroplating layer 6, if there is no insulating layer on the lower surface of the lower conductive layer 1, then 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, then it will not be electroplated.

[0047] After the blind hole 4a is electroplated, a connecting hole conductive column 4b is formed in the blind hole 4a. The connecting hole conductive column 4b physically and electrically connects the lower conductive layer 1 and the upper conductive layer 3. There is a crystal interface between the connecting hole conductive column 4b and the lower conductive layer 1, and between the connecting hole conductive column 4b and the upper conductive layer 3. This is the interface between the electroplated layer and the original conductive layer, and is the weakest part of the blind hole reliability. Among them, the crystal interface 5 between the connecting hole conductive column 4b and the lower conductive layer 1 is the place where the blind hole 4a has the greatest risk of failure. 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 electrical connection between the connecting hole conductive column 4b and the upper conductive layer 1 and the lower conductive layer 3 to fail.

[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, not only shear force, but also tensile stress. At this time, it is divided into the following situations: 1) When the connecting hole conductive column 4b is connected to the lower conductive layer 1 without impurities (lattice defect stress, etc. are not ruled out), the heat of the connecting hole conductive column 4b will be smoothly introduced into the lower conductive layer 1, the temperature gradient between the connecting hole conductive column 4b and the lower conductive layer 1 is small, and the thermal stress (mainly manifested as tensile stress) of the crystal interface 5 connecting the connecting hole conductive column 4b and the lower conductive layer 1 is small, and the connection surface is likely to remain normal. 2) When there are impurities or voids at the crystal interface 5 where the connecting hole conductive column 4b is connected to the lower conductive layer 1, the heat of the connecting hole conductive column 4b will be delayed in being introduced into the lower conductive layer 1, the temperature gradient between the connecting hole conductive column 4b and the lower conductive layer 1 is large, and the crystal interface 5 where the connecting hole conductive column 4b is connected 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 column 4b, and the lower conductive layer 1 and the upper conductive layer 3 are subjected to the tensile stress of the connecting hole conductive column 4b, and finally this tensile stress will act on both ends of the connecting hole conductive column 4b, including the crystal interface 5, and 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 connecting hole conductive column 4b is connected to the lower conductive layer 1, the residual glue has very poor thermal conductivity and expands when heated, directly "exploding" the connecting hole conductive column 4b and the lower conductive layer 1, resulting in mechanical connection failure and electrical connection failure. In this case, the intermediate insulating layer 2 around the connecting hole conductive column 4b and the lower conductive layer 1 expands to produce tensile stress, the shear force generated by the inconsistent thermal expansion of the connecting hole conductive column 4b and the lower conductive layer 1, and the "explosion" pressure generated by the violent expansion of the organic matter between the connecting hole conductive column 4b and the lower conductive layer 1 due to heat. In this case, electrical connection failure will occur first.

[0049] The direction of heat transfer is from high temperature to low temperature. The spatial change of high and low temperature is called temperature gradient. The temperature gradient of the present invention includes laser continuous heating to maintain the local constant temperature state of the circuit board (the heat in the heated area will be constantly dissipated, supplemented by the heat input of laser heating, so the local constant temperature is maintained).

[0050] After laser heating the blind hole by 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] The electrical test of the blind hole is specifically that when the conductive column 4b of the connection hole is connected to the lower conductive layer 1 without impurities, the two ends of the conductive column 4b of the connection hole are electrically tested online or offline afterwards, and the electrical performance of the lower conductive layer 1 and the upper conductive layer 3 connected by the conductive column 4b of the connection hole does not change qualitatively; when there are impurities or gaps in the crystal interface 5 where the conductive column 4b of the connection hole is connected to the lower conductive layer 1 and micro cracks or even fractures are formed due to excessive thermal stress, the electrical performance of the lower conductive layer 1 and the upper conductive layer 3 connected by the conductive column 4b of the connection hole will change qualitatively. The electrical test refers to electrical tests on capacitance, resistance, inductance, voltage, current, etc.; the electrical performance refers to electrical parameters such as capacitance, resistance, inductance, etc.

[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] The four-wire test is to test by introducing the test signal into two of the four pins of the PCB board, and the other two pins receive the return signal; this test method can test all electrical performance parameters, including conduction, insulation, capacitance, inductance and other parameters; specifically, the four-wire test is to test whether the circuit board functions normally by adding four lines, namely VCC, GND, signal output and signal input, to the circuit board. These four lines are respectively connected to the VCC, GND, signal line and input line on the circuit board, and the circuit board is systematically tested to ensure that the circuit board can work normally. The principle of the four-wire test of the circuit board is based on resistance measurement; during the test, the test equipment will inject current into the signal output line of the circuit board and measure the voltage between this signal output line and the signal input line. In this way, the signal input resistance and signal output resistance, as well as the signal output offset voltage and AC coupling and other indicators can be calculated. According to these indicators, it is possible to determine whether the output and input of the circuit board meet the design requirements, and then detect whether the function of the circuit board is normal.

[0054] The two-wire test only tests the resistance value between two pins, and the test is achieved by inserting 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 test of the blind hole is specifically: mechanical test of the connection between the conductive pillar 4b of the connection hole and the crystal interface 5 of the lower conductive layer 1 is performed, and the copper tensile test of the conductive pillar 4b of the connection hole is performed to ensure that the mechanical properties of the connection have not changed. If the tensile test causes the connection to break, the product can be judged as unqualified.

[0056] The metallographic test of the blind hole is specifically performed as follows: metallographic mechanical sectioning is performed on the hole copper, and the crystal interface 5 connecting the connecting hole conductive column 4b with the upper conductive layer 3 and / or the lower conductive layer 1 is observed under a microscope. There is no break or microcrack, indicating 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 the industry's circuit boards has the following disadvantages: 1) Energy consumption. The temperature cycle test heats the entire internal temperature of the test cabinet to increase 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 insulating 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, and cannot achieve online full inspection testing; 4) The maximum temperature cannot exceed the temperature that the insulating 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 insulating 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) online testing can be achieved. The laser beam can efficiently perform local heating tests. If the heating test (equivalent to the aging test) is passed, the next process can be carried out, and those that fail to pass will be directly scrapped; 4) local high temperature testing can be achieved. 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), thereby obtaining a large temperature gradient. This 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 test of the internal temperature of the circuit board, that is, the internal temperature gradient of the circuit board is small, and the invention can achieve 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, the heat sink is an object that can quickly conduct heat away. The heat sink allows the circuit board attached to it to dissipate heat naturally and passively or actively dissipate heat at a controlled temperature. This method of adding a heat sink allows the heat to be conducted faster in areas away from the laser heating point, which can intensify the temperature gradient of the thermal field and further improve the detection effect 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 pointing 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 pointing from the lower conductive layer to the upper conductive layer; or the laser beam can be emitted toward the upper conductive layer and the lower conductive layer simultaneously or successively (when the laser beam is emitted toward the upper conductive layer and the lower conductive layer simultaneously, the laser beam is provided with two beams, which are emitted toward the upper conductive layer and the lower conductive layer respectively). It is preferred that the heating point of the laser beam on the conductive material is closest to the crystal interface between the conductive column of the connecting hole and the lower conductive layer, so that the 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 surface 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 75 micron thick circuit board high-speed insulating material, the upper aperture of the blind hole 4a is 150 microns, and the lower aperture is 120 microns. After chemical copper deposition and hole-filling electroplating and other processes, the connecting hole conductive column 4b fills the blind hole 4a, and the surface electroplating layer 6 is 10 microns thick. The biggest risk point of the blind hole reliability lies in the bonding force 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 opening of the blind hole in the upper conductive layer 3. The blind hole is then sliced, as shown in FIG. Figure 5 As shown, if there is no crack, break or gap on 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, as shown by 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 is not passed, and the blind hole determination is unreliable. The specific reasons are analyzed by other processes.

[0068] Another example: Figure 3 As shown, the upper conductive layer 3 is 12 microns thick copper, the lower conductive layer 1 is 12 microns thick copper foil, 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 25 microns thick PI polyimide insulating material, the upper aperture of the blind hole 4a is 100 microns, and the lower aperture is 80 microns. After black hole and electroplating processes, the surface electroplating layer 6 is 10 microns thick, and 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 the 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 in the figure will also be electroplated with 10 microns of copper, which is not marked in the figure). Then the blind hole is sliced, such as Figure 7 As shown, if there is no crack, break or gap on the crystal interface 5, it indicates that the blind hole is reliable; if there is Figure 6 If there is a gap at the crystal interface 5 shown, such as gap 9 at the bottom of the blind hole (for the convenience of expression, gap 9 is marked at the bottom of another blind hole), then the temperature shock test of the blind hole will not pass, and the blind hole determination is 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 specifically includes: 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 that a high and low temperature cycle aging test of the blind hole reliability can be achieved.

[0072] Preferably, in the step one, aiming the blind hole for laser heating to apply a thermal field specifically includes: in the spatial dimension, aiming the blind hole for laser fixed-point impact heating or / and scanning motion heating 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, laser beam scanning heating can be used.

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

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

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

[0077] Specifically, the so-called online testing is to use the test equipment as a process of the circuit board production line to conduct random or full inspection of the reliability of the blind holes of the circuit board. Offline testing cannot be performed on the circuit board production line, but is taken to the physical laboratory for separate sampling and sampling testing.

[0078] Preferably, 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.

[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 lateral 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; including 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 of multiple 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 of the connection hole and the upper conductive layer and / or the lower conductive layer. The so-called optimal refers to the maximum destructive stress that can be formed.

[0085] Preferably, the upper conductive layer is generated 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 for production at present, that is, a lower conductive layer and an insulating layer are first formed, and then a blind hole is laser drilled, and an electroplating seed layer is formed by chemical copper deposition or ion sputtering injection, and then electroplating is used to thicken the layer to form connecting hole conductive columns and an upper conductive layer.

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

[0088] Specifically, a single-order 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 penetrates 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 connecting hole conductive column 5 and the third conductive layer 11. This is a second-order blind hole; multi-order blind holes above the second order are similar.

[0090] like Fig. 9 As shown, a plurality of first-order blind holes are stacked in sequence, which is a stacked hole. Among them, the lower conductive layer 1 is attached to the second intermediate insulating layer 21, the second intermediate insulating layer 21 is attached to the third conductive layer 11, the third intermediate insulating layer 22 is attached to the third conductive layer 11, and the fourth conductive layer 111 is attached to the third intermediate insulating layer 22.

[0091] like Fig.10 If the connection hole conductive column 4b 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 any combination of multiple materials.

[0095] Embodiment 2:

[0096] The present invention provides a blind hole reliability test device, which is used for performing reliability test on blind holes on a circuit board, wherein the circuit board at least comprises a stacked lower conductive layer, an intermediate insulating layer and an upper conductive layer; a connecting hole conductive column is arranged 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 is connected 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 emitting the output laser beam to 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 column of the connecting hole and the lower conductive layer, and forming a temperature gradient between the conductive area of ​​the circuit board and the intermediate insulating layer around 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 column is lower than the melting temperature of the connecting hole conductive column; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive column 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 hole to determine the reliability of the electrical connection between the conductive column of the connection hole and the lower conductive layer and / or the upper conductive layer.

[0104] Embodiment three:

[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 blind hole reliability testing method as described above is implemented when the computer program is executed.

[0106] Embodiment 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 platform 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 to 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 connecting hole conductive column 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 around 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 column is lower than the melting temperature of the connecting hole conductive column; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive column and the upper conductive layer and the lower conductive layer;

[0112] The blind hole is subjected to electrical testing, mechanical testing or metallographic testing to determine the reliability of the electrical connection between the conductive column of the connection hole and the lower conductive layer and / or the upper conductive layer.

[0113] The blind hole 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 laser beam to heat near the key point position of blind hole reliability detection to form a thermal field with a large temperature gradient. The thermal field brings tensile stress and shear stress to the crystal interface at the bottom of the blind hole. The impact strength of the blind hole bottom detection is much higher than the detection impact strength of conventional temperature cycles. Due to the existence of the temperature gradient, the heating of the electroplated copper in the blind hole can be much higher than the bearing 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 a higher blind hole reliability detection standard.

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

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

[0117] 4) Full inspection of blind holes can be achieved. Traditional temperature cycle shock tests are destructive tests, which belong to sample sampling tests, and then the production line parameters are evaluated. Due to the high efficiency of the detection, the method of the present invention can achieve full inspection of blind holes in the production line circuit board, and unqualified products are eliminated, and qualified products are retained (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 a very limited laser heating of the blind hole, and the blind hole 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, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present 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 may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0120] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A blind hole reliability testing method, characterized in that: A reliability test is performed on a blind hole on a circuit board, wherein the circuit board at least comprises 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 is connected to the lower conductive layer at the hole bottom of the blind hole; The blind hole reliability testing method comprises: Step 1: directing a laser beam toward the circuit board and aligning the blind hole for laser heating to apply a thermal field, thereby forming a temperature gradient on the upper conductive layer, the conductive column of the connecting 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 around 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 column is lower than the melting temperature of the connecting hole conductive column; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive column and the upper conductive layer and the lower conductive layer; Step 2: 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 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 includes: 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, laser heating is performed on the blind hole to apply a thermal field. Specifically, in the time dimension, laser intermittent or cyclic heating is performed on the blind hole to apply a thermal field.

5. The blind hole reliability testing method according to claim 1, characterized in that: In the step 1, laser heating is performed on the blind hole to apply a thermal field, specifically: in the spatial dimension, laser fixed-point impact heating or / and scanning motion heating is performed 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, aiming the blind hole for laser heating to apply a thermal field specifically includes: aiming a single blind hole for laser heating to apply a thermal field, or aiming a plurality of blind holes for laser heating to apply a thermal field simultaneously or successively.

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 electrical series and / or parallel electrical tests on the plurality of blind holes.

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

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 hole reliability testing method according to claim 1, characterized in that: The laser beam is a composite laser beam.

11. The blind hole reliability testing method according to claim 1, characterized in that: 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 of multiple thereof.

12. The blind hole reliability testing method according to claim 1, characterized in that: The upper conductive layer is generated by electroplating together with the connecting hole conductive pillars in the blind holes.

13. The blind hole reliability testing method according to claim 1, characterized in that: The blind vias include any one of single-order blind vias, multi-order blind vias, stacked vias and cross-layer blind vias, or any combination of multiple thereof.

14. The blind hole reliability testing method according to claim 1, characterized in that: The conductive metal material of the upper conductive layer, the conductive pillar of the connection hole 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 any combination of multiple materials.

15. A blind hole reliability testing device, characterized in that: Used to perform reliability test on blind holes on a circuit board, the circuit board at least comprising 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 is connected to the lower conductive layer at the hole bottom of the blind hole; 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 emitting the output laser beam to 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 column of the connecting hole and the lower conductive layer, and forming a temperature gradient between the conductive area of ​​the circuit board and the intermediate insulating layer around 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 column is lower than the melting temperature of the connecting hole conductive column; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive column 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 hole to determine the reliability of the electrical connection between the conductive column of 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 as claimed in 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 as claimed in claim 16, wherein the blind hole reliability testing device is electrically connected to the laser; The machine platform 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 to 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 connecting hole conductive column 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 around 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 column is lower than the melting temperature of the connecting hole conductive column; the thermal field with a temperature gradient forms a stress field between the connecting hole conductive column and the upper conductive layer and the lower conductive layer; The blind hole is subjected to electrical testing, mechanical testing or metallographic testing to determine the reliability of the electrical connection between the conductive column of the connection hole and the lower conductive layer and / or the upper conductive layer.

Images