Method for processing coreless packaging substrate and coreless packaging substrate

Abstract

The embodiment of the present application provides a processing method of coreless packaging substrate and the coreless packaging substrate, which comprises the following steps: providing a support plate, wherein the support plate comprises a base material, a first copper foil attached to two sides of the base material, and a second copper foil attached to the first copper foil; pressing a first prepreg and a third copper foil on the second copper foil; performing a pattern making on the third copper foil to form a circuit pattern; pressing a second prepreg and a fourth copper foil on the third copper foil, wherein the thickness of the second prepreg is different from the thickness of the first prepreg, so that the thickness of a second dielectric layer formed by curing the second prepreg is the same as the thickness of a first dielectric layer formed by curing the first prepreg; and separating the first copper foil from the second copper foil to obtain two coreless packaging substrates. The processing method of the embodiment of the present application can reduce the warping of the substrate caused by the uneven stress of the first dielectric layer and the second dielectric layer, thereby reducing the warping degree of the coreless packaging substrate and improving the production yield of subsequent processes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of packaging substrate processing, in particular to a processing method of coreless packaging substrate and coreless packaging substrate. BACKGROUND

[0002] With the development of ultra-thin semiconductor chips, the requirement for ultra-thin packaging substrate is also higher and higher. The coreless packaging substrate has the advantage of thinner plate thickness compared with the conventional packaging substrate because the core layer is removed. The material of each dielectric layer of the coreless packaging substrate is a prepreg formed by impregnating BT resin into glass cloth, and high temperature and high pressure are needed to make the prepreg bond and solidify during layering.

[0003] At present, the same thickness of prepreg is used to press each layer during layering of the coreless packaging substrate. Due to the difference in copper thickness and residual copper rate of each layer, the thickness of each dielectric layer after actual solidification of the prepreg is obviously different. The stress generated after solidification and shrinkage of each dielectric layer with inconsistent thickness is uneven, and the warpage of the coreless packaging substrate without the support of the core layer is as high as 15-30 mm, which seriously affects the production and processing of subsequent processes. SUMMARY

[0004] The embodiment of the present application provides a processing method of coreless packaging substrate and coreless packaging substrate, which can reduce the warpage of the coreless packaging substrate and improve the production yield of subsequent processes.

[0005] The embodiment of the present application provides a processing method of coreless packaging substrate, which comprises the following steps:

[0006] A support plate is provided, which comprises a base material, a first copper foil attached to both sides of the base material, and a second copper foil attached to the first copper foil;

[0007] A first prepreg and a third copper foil are pressed on the second copper foil;

[0008] A pattern is made on the third copper foil to form a circuit pattern;

[0009] A second prepreg and a fourth copper foil are pressed on the third copper foil, wherein the thickness of the second prepreg is different from that of the first prepreg, so that the thickness of a second dielectric layer formed by solidification of the second prepreg is the same as that of a first dielectric layer formed by solidification of the first prepreg;

[0010] The first copper foil and the second copper foil are separated to obtain two coreless packaging substrates, which comprise the second copper foil, the first prepreg, the third copper foil, the second prepreg and the fourth copper foil which are sequentially stacked.

[0011] In some embodiments, before pressing the first prepreg and the third copper foil on the second copper foil, further comprising: performing a first drilling to form a plurality of first through holes passing from one side of the second copper foil to the other side of the second copper foil;

[0012] After pressing the first prepreg and the third copper foil on the second copper foil, further comprising: performing a second drilling to form a plurality of second through holes passing from one side of the third copper foil to the other side of the third copper foil.

[0013] In some embodiments, the thickness of the first dielectric layer is calculated according to the following formula:

[0014] Te1 = Ta - 3.14 * (D1 / 2)2 * N1 * t / S

[0015] Wherein, Te1 is the thickness of the first dielectric layer, Ta is the thickness of the first prepreg, D1 is the hole diameter of the first through hole, N1 is the number of the first through hole, t is the thickness of the coreless packaging substrate, and S is the area of the coreless packaging substrate.

[0016] In some embodiments, the thickness of the second dielectric layer is calculated according to the following formula:

[0017] Te2 = Tb - 3.14 * (D2 / 2)2 * N2 * t / S - Tc * (1-c%)

[0018] Wherein, Te2 is the thickness of the second dielectric layer, Tb is the thickness of the second prepreg, D2 is the hole diameter of the second through hole, N2 is the number of the second through hole, Tc is the thickness of the third copper foil, and c% is the residual copper rate of the third copper foil after forming a circuit pattern.

[0019] In some embodiments, the pressing condition of pressing the first prepreg and the third copper foil on the second copper foil is different from the pressing condition of pressing the second prepreg and the fourth copper foil on the third copper foil, so that the resin overflow amount of the first prepreg is greater than that of the second prepreg.

[0020] In some embodiments, the temperature rising rate when pressing the first prepreg and the third copper foil on the second copper foil is less than the temperature rising rate when pressing the second prepreg and the fourth copper foil on the third copper foil, so as to prolong the melt flow time of the first prepreg.

[0021] In some embodiments, the high pressure temperature when pressing the first prepreg and the third copper foil on the second copper foil is lower than the high pressure temperature when pressing the second prepreg and the fourth copper foil on the third copper foil, so as to accelerate the resin flowability of the first prepreg.

[0022] In some embodiments, the maximum pressure when pressing the first prepreg and the third copper foil on the second copper foil is greater than the maximum pressure when pressing the second prepreg and the fourth copper foil on the third copper foil, so as to accelerate the resin flowability of the first prepreg.

[0023] In some embodiments, the roughness of the second copper foil is greater than the roughness of the fourth copper foil, so that the filling amount of the first prepreg to the second copper foil is greater than the filling amount of the second prepreg to the fourth copper foil.

[0024] The embodiments of the present application also provide a coreless packaging substrate prepared by the processing method.

[0025] In the processing method of the coreless packaging substrate provided by the embodiments of the present application, the thickness of the second prepreg is different from the thickness of the first prepreg, so that the thickness of the second dielectric layer formed by curing the second prepreg is the same as the thickness of the first dielectric layer formed by curing the first prepreg. Therefore, after separating the first copper foil and the second copper foil to obtain two coreless packaging substrates, the stress generated by curing and shrinking of the first dielectric layer and the second dielectric layer of the coreless packaging substrate is uniform, and the warpage of the coreless packaging substrate caused by the non-uniform stress is reduced, so that the warpage of the coreless packaging substrate is reduced, and the production yield of subsequent processes is improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1 The first flowchart of the processing method of the coreless packaging substrate of the embodiments of the present application.

[0028] Figure 2 The schematic diagram of the supporting plate provided by the processing method of the embodiments of the present application.

[0029] Figure 3 The schematic diagram of pressing the first prepreg and the third copper foil in the processing method of the embodiments of the present application.

[0030] Figure 4 The schematic diagram of forming a circuit pattern on the third copper foil in the processing method of the embodiments of the present application.

[0031] Figure 5 The schematic diagram of pressing the second prepreg and the fourth copper foil in the processing method of the embodiments of the present application.

[0032] Figure 6 A schematic diagram of a coreless packaging substrate obtained by the processing method of the embodiment of the present application.

[0033] Figure 7 A second flowchart of the processing method of the coreless packaging substrate of the embodiment of the present application.

[0034] Figure 8 A comparison table of the thickness of the dielectric layer and the warpage of the coreless packaging substrate of the traditional scheme and the scheme of the present application.

[0035] Figure 9 A temperature-pressure curve diagram of the processing method of the embodiment of the present application for pressing the first prepreg and the third copper foil.

[0036] Figure 10 A temperature-pressure curve diagram of the processing method of the embodiment of the present application for pressing the second prepreg and the fourth copper foil. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0038] The processing method of the coreless packaging substrate provided by the embodiments of the present application can reduce the warpage of the coreless packaging substrate and improve the production yield of subsequent processes.

[0039] REFERENCE Figure 1 , Figure 1 A first flowchart of the processing method of the coreless packaging substrate of the embodiment of the present application. The processing method comprises the following steps:

[0040] 11. A support plate is provided, which comprises a base material, a first copper foil attached to both sides of the base material, and a second copper foil attached to the first copper foil;

[0041] 12. The first prepreg and the third copper foil are pressed on the second copper foil;

[0042] 13. Pattern making is performed on the third copper foil to form a circuit pattern;

[0043] 14. The second prepreg and the fourth copper foil are pressed on the third copper foil, wherein the thickness of the second prepreg is different from the thickness of the first prepreg, so that the thickness of the second dielectric layer formed by curing the second prepreg is the same as the thickness of the first dielectric layer formed by curing the first prepreg;

[0044] 15, separating the first copper foil from the second copper foil to obtain two coreless packaging substrates, each of which comprises the second copper foil, the first prepreg, the third copper foil, the second prepreg, and the fourth copper foil which are sequentially stacked.

[0045] With reference to Figures 2 to 6 , Figure 2 a schematic view of a support plate for a processing method of an embodiment of the present application, Figure 3 a schematic view of pressing a first prepreg and a third copper foil for a processing method of an embodiment of the present application, Figure 4 a schematic view of forming a circuit pattern on a third copper foil for a processing method of an embodiment of the present application, Figure 5 a schematic view of pressing a second prepreg and a fourth copper foil for a processing method of an embodiment of the present application, Figure 6 a schematic view of separating to obtain a coreless packaging substrate for a processing method of an embodiment of the present application.

[0046] First, a support plate is provided, which serves as a support material in the subsequent pressing process. The support plate can be referred to as Detach Core. As shown in Figure 2 , the support plate comprises a base material 21, a first copper foil 22 attached to both sides of the base material 21, and a second copper foil 23 attached to the first copper foil 22. In one example, the thickness of the first copper foil 22 is 18um, and the thickness of the second copper foil 23 is 3um. The first copper foil 22 is a carrier copper foil, and the second copper foil 23 is an ultra-thin copper foil.

[0047] Subsequently, a first prepreg 24 and a third copper foil 25 are pressed on the second copper foil 23, as shown in Figure 3 . It should be noted that the first prepreg 24 and the third copper foil 25 are pressed on the second copper foil 23 on each side. The pressing process needs to be carried out at a certain temperature and pressure. In one example, the thickness of the third copper foil 25 is 12um.

[0048] Subsequently, patterning is performed on the third copper foil 25 to form a circuit pattern, as shown in Figure 4 , a circuit pattern 251 is formed on the third copper foil 25. Specifically, the circuit pattern 251 can be formed by processes such as film pasting, exposure, development, and etching.

[0049] Subsequently, as shown in Figure 5As shown, the second prepreg 26 and the fourth copper foil 27 are laminated on the third copper foil 25. The thickness of the second prepreg 26 is different from the thickness of the first prepreg 24, so that the thickness of the second dielectric layer formed by curing the second prepreg 26 is the same as the thickness of the first dielectric layer formed by curing the first prepreg 24. Specifically, the thickness of the second prepreg 26 can be calculated according to the thickness of the first prepreg 24 and the requirement that the thickness of the second dielectric layer is the same as the thickness of the first dielectric layer. It should be noted that the second prepreg 26 and the fourth copper foil 27 are laminated on each side of the third copper foil 25. The lamination process also needs to be carried out at a certain temperature and pressure. In an example, the fourth copper foil 27 is an ultra-thin copper foil with a thickness of 3 um.

[0050] Subsequently, the first copper foil 22 is separated from the second copper foil 23 to obtain two coreless packaging substrates. As shown in Figure 6 The coreless packaging substrate includes the second copper foil 23, the first prepreg 24, the third copper foil 25, the second prepreg 26, and the fourth copper foil 27 which are sequentially stacked.

[0051] It can be understood that, in the embodiment of the present application, the thickness of the second prepreg 26 is different from the thickness of the first prepreg 24, which can make the thickness of the second dielectric layer formed by curing the second prepreg 26 the same as the thickness of the first dielectric layer formed by curing the first prepreg 24. Therefore, after the first copper foil 22 is separated from the second copper foil 23 to obtain two coreless packaging substrates, it can be ensured that the stress caused by the curing shrinkage of the first dielectric layer and the second dielectric layer of the coreless packaging substrate is uniform, and the warpage of the coreless packaging substrate caused by the non-uniform stress is reduced. Therefore, the warpage of the coreless packaging substrate can be reduced, and the production yield of the subsequent process can be improved.

[0052] According to the data obtained by actual detection, the warpage of the coreless packaging substrate of the prior art is as high as 15-30 mm, which leads to a horizontal line clamping plate failure rate of more than 10% in the subsequent process. However, the warpage of the coreless packaging substrate of the embodiment of the present application can be controlled within 10 mm, so that the horizontal line clamping plate failure rate in the subsequent process is reduced to within 0.5%. It can be seen that the coreless packaging substrate of the embodiment of the present application can greatly reduce the warpage of the coreless packaging substrate, thereby greatly reducing the failure rate of the subsequent process and improving the production yield.

[0053] In some embodiments, reference Figure 7 , Figure 7 is a second flow diagram of the processing method of the coreless packaging substrate of the embodiment of the present application.

[0054] In step 12, before laminating the first prepreg and the third copper foil on the second copper foil, step 16 of performing first drilling is further included to form a plurality of first through holes penetrating from one side of the second copper foil to the other side of the second copper foil.

[0055] Step 12, after the first prepreg and the third copper foil are laminated on the second copper foil, further comprises step 17: performing a second drilling to form a plurality of second through holes passing through the third copper foil from one side to the other side.

[0056] The first drilling forms a plurality of first through holes passing through the second copper foil 23 from one side to the other side on the support plate. In practical applications, the first through holes are formed in the edge area of the support plate, and the first through holes are used for positioning in subsequent processes and for edge sealing to prevent accidental separation between the first copper foil 22 and the second copper foil 23.

[0057] The second drilling forms a plurality of second through holes passing through the third copper foil 25 from one side to the other side. In practical applications, the second through holes are also formed in the edge area of the support plate, and the second through holes can also be used for positioning in subsequent processes.

[0058] In some embodiments, in order to make the thickness of the second dielectric layer formed by curing the second prepreg 26 the same as the thickness of the first dielectric layer formed by curing the first prepreg 24, the thickness of the first prepreg 24 and the second prepreg 26 can be set and calculated as follows:

[0059] When the first prepreg 24 is laminated, the second copper foil 23 at the bottom and the third copper foil 25 at the top are both light copper foils without circuit patterns, i.e., the residual copper rate is 100%. According to the principle that the volume of the prepreg resin remains unchanged during lamination, it can be calculated that the thickness of the first dielectric layer formed by curing the first prepreg 24 is equal to the thickness of the first prepreg 24 minus the portion of the resin filled into the first through holes, i.e., the thickness of the first dielectric layer is calculated according to the following formula:

[0060] Te1=(Ta*S-3.14*(D1 / 2)²*N1*t) / S=Ta-3.14*(D1 / 2)²*N1*t / S

[0061] Wherein, Te1 is the thickness of the first dielectric layer, Ta is the thickness of the first prepreg 24, D1 is the diameter of the first through hole, N1 is the number of the first through hole, t is the thickness of the coreless packaging substrate, and S is the area of the coreless packaging substrate (i.e., the area of one side of the support plate).

[0062] When the second prepreg 26 is laminated, the third copper foil 25 on the bottom of the second prepreg 26 is etched to form a circuit pattern 251, and the residual copper rate is c%. The fourth copper foil 27 on the top of the second prepreg 26 is a light copper foil without a circuit pattern, that is, the residual copper rate is 100%. According to the principle that the volume of the prepreg resin does not change when laminated, it can be calculated that the thickness of the second dielectric layer formed by curing the second prepreg 26 is equal to the thickness of the second prepreg 26 minus the part of the resin filled into the second through hole and the resin filled into the gap part of the circuit pattern 251, that is, the thickness of the second dielectric layer is calculated according to the following formula:

[0063] Te2=(Tb*S-3.14*(D2 / 2)²*N2*t- Tc*(1-c%)*S) / S=Tb-3.14*(D2 / 2)²*N2*t / S-Tc*(1-c%)

[0064] wherein Te2 is the thickness of the second dielectric layer, Tb is the thickness of the second prepreg 26, D2 is the aperture of the second through hole, N2 is the number of the second through hole, t is the thickness of the coreless packaging substrate, S is the area of the coreless packaging substrate (that is, the area of one side of the support plate), Tc is the thickness of the third copper foil 25, and c% is the residual copper rate of the third copper foil 25 after etching to form the circuit pattern 251.

[0065] It should be noted that since the third copper foil 25 is etched to form the circuit pattern 251, the residual copper rate is c%, and the non-copper base material area leaked after the entire copper layer is etched to form the circuit pattern 251 needs to be filled with prepreg resin flow, which will cause the thickness of the second dielectric layer on the third copper foil 25 to decrease, so when calculating Te2 in the above formula, the value of the decrease in the thickness of the second dielectric layer caused by the filling of the prepreg resin flow in the non-copper base material area of the third copper foil 25 needs to be subtracted, that is, Tc*(1-c%) is subtracted.

[0066] In the embodiment of the present application, the thickness of the second dielectric layer is the same as the thickness of the first dielectric layer, that is, Te2=Te1. Therefore, the thickness Tb of the second prepreg 26 can be calculated according to the thickness Ta of the first prepreg 24, and the calculation formula is as follows:

[0067] Tb=Ta-3.14*(D1 / 2)²*N1 / S+3.14*(D2 / 2)²*N2 / S+Tc*(1-c%)

[0068] For example, the thicknesses of the prepregs used for twice lamination of a 3-layer coreless packaging substrate are as follows:

[0069] The first prepreg 24 used in the first lamination has a thickness Ta=20um, a first through-hole diameter D1=0.25mm, a first through-hole number N1=10000, a second through-hole diameter D2=0.25mm, a second through-hole number N2=20000, a third copper foil 25 has a thickness Tc=12um, and the residual copper rate after the third copper foil 25 forms the circuit pattern 251 is 50%. The package substrate area S=513mm*623mm=319599mm², so the final calculated thickness Tb of the second prepreg 26 is 26um.

[0070] It should be noted that in practical applications, the diameters of the first through-hole (D1) and the second through-hole (D2) range from 0.25mm to 3.00mm, and the number of the first through-hole (N1) and the number of the second through-hole (N2) range from tens of thousands to millions. Smaller through-hole diameters and fewer through-holes have a smaller impact on the calculation of the thickness Tb of the second prepreg 26; larger through-hole diameters and more through-holes have a greater impact on the calculation of the thickness Tb of the second prepreg 26. In the example above, the diameters of the first through hole D1 and the second through hole D2 are both 0.25 mm, the number of the first through holes N1 = 10000, and the number of the second through holes N2 = 20000. The values ​​of the through hole diameter and the number of through holes are very small, so they have little impact on the calculation of the thickness Tb of the second prepreg 26. As the value of the through hole diameter and the value of the number of through holes increase, the impact on the calculation of the thickness Tb of the second prepreg 26 will become more and more obvious.

[0071] refer to Figure 8 , Figure 8 This table compares experimental data on dielectric layer thickness and warpage of the coreless packaging substrate between conventional and proposed solutions. Figure 8 As can be seen, in traditional solutions, the difference between the thickness of the first dielectric layer and the second dielectric layer is significant, resulting in a warpage of 13mm to 20mm for the coreless packaging substrate. In the solution of this application, the difference between the thickness of the first dielectric layer and the second dielectric layer is very small, and their thicknesses are very close, resulting in a warpage of 5mm to 8mm for the coreless packaging substrate. Therefore, the solution of this application can significantly improve the warpage of the coreless packaging substrate.

[0072] In practical applications, the selection of prepreg series and models is mainly based on the dielectric constant Dk and dielectric loss Df. To ensure its functionality, each dielectric layer should use the same series of prepreg, and the thickness of the same series of prepreg is determined by the glass fiber model and the resin content. The standard thickness of each model of the same series is defined by the manufacturer and cannot be adjusted at will. For example, in the GHPL-830NS series prepreg on the market, the standard thickness of different resin contents of #1017 glass fiber is as follows: SF66 #1017 thickness 20um, SF68 #1017 thickness 22um, SF70 #1017 thickness 24um, SF74 #1017 thickness 29um, SF76 #1017 thickness 32um, SF78 #1017 thickness 35um.

[0073] In the above example, when SF66 #1017 is used as the first prepreg 24 for the first pressing, there is no 26um prepreg to choose as the second prepreg 26. At this time, the second prepreg 26 selects the closest SF70 #1017 with a thickness of 24um, so the thickness of the second dielectric layer Te2 after pressing and curing is still 2um less than the thickness of the first dielectric layer Te1. Therefore, in order to reduce the warpage caused by the thickness difference between the first dielectric layer and the second dielectric layer, further optimization and improvement are needed.

[0074] In some embodiments, to further reduce the warpage caused by the thickness difference between the first dielectric layer and the second dielectric layer, the pressing conditions for pressing the first prepreg 24 and the third copper foil 25 on the second copper foil 23 are different from the pressing conditions for pressing the second prepreg 26 and the fourth copper foil 27 on the third copper foil 25, so that the resin overflow amount of the first prepreg 24 is greater than the resin overflow amount of the second prepreg 26, thereby making the thickness of the first dielectric layer and the thickness of the second dielectric layer approach or equal.

[0075] In some embodiments, the heating rate when pressing the first prepreg 24 and the third copper foil 25 on the second copper foil 23 is less than the heating rate when pressing the second prepreg 26 and the fourth copper foil 27 on the third copper foil 25, so as to prolong the melting flow time of the first prepreg 24.

[0076] For example, in one example, when pressing the first prepreg 24 and the third copper foil 25 on the second copper foil 23, the heating rate is 2.0℃ / min~2.5℃ / min; when pressing the second prepreg 26 and the fourth copper foil 27 on the third copper foil 25, the heating rate is 3.0℃ / min~3.5℃ / min. Therefore, compared with the second prepreg 26, the melting flow time of the first prepreg 24 can be prolonged, and the overflow amount of the first prepreg 24 during pressing can be increased.

[0077] In some embodiments, the high-voltage transition temperature when pressing the first prepreg 24 and the third copper foil 25 onto the second copper foil 23 is lower than the high-voltage transition temperature when pressing the second prepreg 26 and the fourth copper foil 27 onto the third copper foil 25, so as to accelerate the resin flowability of the first prepreg 24.

[0078] For example, in one instance, when pressing the first prepreg 24 and the third copper foil 25 onto the second copper foil 23, the high-pressure transition temperature is 130°C to 140°C; when pressing the second prepreg 26 and the fourth copper foil 27 onto the third copper foil 25, the high-pressure transition temperature is 150°C to 160°C. Therefore, it is possible to accelerate resin flow by applying high pressure before the lowest viscosity point of the first prepreg 24.

[0079] In some embodiments, the highest pressure when pressing the first prepreg 24 and the third copper foil 25 onto the second copper foil 23 is greater than the highest pressure when pressing the second prepreg 26 and the fourth copper foil 27 onto the third copper foil 25, so as to accelerate the resin flowability of the first prepreg 24.

[0080] For example, in one instance, when the first prepreg 24 and the third copper foil 25 are pressed onto the second copper foil 23, the maximum pressure is 45 kg / cm² to 50 kg / cm²; when the second prepreg 26 and the fourth copper foil 27 are pressed onto the third copper foil 25, the maximum pressure is 35 kg / cm² to 40 kg / cm². Therefore, the pressure on the resin in the first prepreg 24 promotes resin flow.

[0081] refer to Figure 9 and Figure 10 , Figure 9 This is a temperature and pressure curve diagram of the processing method of this application for pressing the first prepreg 24 and the third copper foil 25 together. Figure 10 This is a temperature and pressure curve of the processing method of this application for pressing the second semi-cured sheet 26 and the fourth copper foil 27 together. Figure 9 Semi-cured sheet A indicates the first semi-cured sheet 24. Figure 10 The term "medium-prepreg B" indicates the second half-prepreg, 26.

[0082] like Figure 9 As shown, the temperature settings for the prepreg A lamination process are as follows: the first stage temperature rises from the initial temperature of 30~50℃ to 180℃ in 40~50 minutes; the second stage temperature is 180℃ and held for 20~30 minutes; the third stage temperature rises from 180℃ to 220℃ in 5~10 minutes; the fourth stage temperature is 220℃ and held for 90~110 minutes; and the fifth stage temperature drops from 220℃ to 40~60℃ in 40~60 minutes.

[0083] The pressing program of prepreg A is set as follows: the initial pressure is set to 5-10 kg / cm2 in the first stage, and the pressure is kept constant for 10-15 min; the pressure is raised from 5-10 kg / cm2 to 25-35 kg / cm2 in the second stage for 5-10 min; the pressure is kept constant at 25-35 kg / cm2 for 10-15 min in the third stage; the pressure is raised from 25-35 kg / cm2 to 45-50 kg / cm2 in the fourth stage for 10-20 min; the pressure is kept constant at 45-50 kg / cm2 for 140-160 min in the fifth stage; and the pressure is reduced from 45-50 kg / cm2 to 5-10 kg / cm2 in the sixth stage, and then kept constant for 30-40 min.

[0084] As shown in Figure 10 The pressing program of prepreg B is set as follows: the temperature is raised from the initial temperature of 30-50 °C to 180 °C in the first stage for 25-35 min; the temperature is kept constant at 180 °C for 35-45 min in the second stage; the temperature is raised from 180 °C to 220 °C in the third stage for 5-10 min; the temperature is kept constant at 220 °C for 90-110 min in the fourth stage; the temperature is reduced from 220 °C to 40-60 °C in the fifth stage for 40-60 min.

[0085] The pressing program of prepreg B is set as follows: the initial pressure is set to 5-10 kg / cm2 in the first stage, and the pressure is kept constant for 15-20 min; the pressure is raised from 5-10 kg / cm2 to 25-35 kg / cm2 in the second stage for 5-10 min; the pressure is kept constant at 25-35 kg / cm2 for 15-20 min in the third stage; the pressure is raised from 25-35 kg / cm2 to 45-50 kg / cm2 in the fourth stage for 15-25 min; the pressure is kept constant at 45-50 kg / cm2 for 130-150 min in the fifth stage; and the pressure is reduced from 45-50 kg / cm2 to 5-10 kg / cm2 in the sixth stage, and then kept constant for 30-40 min.

[0086] Through the above adjustment of the pressing conditions of the first prepreg 24 and the second prepreg 26, the glue overflow amount of the first prepreg 24 can be increased from 3%-5% before adjustment to 8%-10%, which is about 5% higher than before adjustment, and the thickness after pressing and curing can be reduced by 20 um*5%=1 um. At this time, the thickness Te2 of the second dielectric layer is 1 um less than the thickness Te1 of the first dielectric layer, so the thickness difference between the second dielectric layer and the first dielectric layer can be further reduced, thereby further reducing the warpage of the coreless packaging substrate.

[0087] In some embodiments, to further reduce the warpage caused by the difference in thickness between the first dielectric layer and the second dielectric layer, the roughness of the second copper foil 23 can be made greater than the roughness of the fourth copper foil 27, so that the filling amount of the first prepreg 24 to the second copper foil 23 is greater than the filling amount of the second prepreg 26 to the fourth copper foil 27.

[0088] For example, in one example, the second copper foil 23 can use an ultra-low copper tooth roughness copper foil with Rz=2.2um, and the fourth copper foil 27 can use an extremely low copper tooth roughness copper foil with Rz=1.3um. Therefore, the filling amount of the first prepreg 24 to the second copper foil 23 is 2.2um*(1 / 2)-1.3um*(1 / 2)=0.45um greater than the filling amount of the second prepreg 26 to the fourth copper foil 27. At this time, the thickness Te2 of the second dielectric layer is reduced by 1um to 0.55um less than the thickness Te1 of the first dielectric layer. Therefore, the thickness difference between the second dielectric layer and the first dielectric layer can be further reduced, thereby further reducing the warpage of the coreless packaging substrate.

[0089] In practical applications, there are various specifications for the copper tooth roughness of copper foils with different thicknesses. For example, when the 3um thick copper foil is replaced by a 12um thick copper foil, the copper tooth roughness thereof has 1.5~4.5 to choose from, and the maximum impact on the difference in thickness of the dielectric layer is 4.5um*(1 / 2)-1.5um*(1 / 2)=1.5um.

[0090] The above uses various ways such as prepregs with different thicknesses (including adhesive content), adjusting the pressing conditions of the prepregs to control the resin overflow amount of the prepregs, and using copper foils with different copper tooth roughnesses to jointly reduce the thickness difference between the first dielectric layer and the second dielectric layer, thereby reducing the warpage of the coreless packaging substrate. In practical applications, one or a combination of multiple ways can be selected according to the actual product situation to minimize the warpage of the coreless packaging substrate obtained finally.

[0091] The embodiments of the present application also provide a coreless packaging substrate prepared by the processing method of any of the above embodiments.

[0092] In the description of the present application, it should be understood that terms such as "first", "second" and the like are only used to distinguish similar objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated.

[0093] The processing method of the coreless packaging substrate and the coreless packaging substrate provided by the embodiments of the present application are described in detail above. The principles and implementation manners of the present application are described by applying specific examples in this paper, and the above description of the embodiments is only used to help understand the present application. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed, and the above description of the present application should not be understood as a limitation.

Claims

1. A processing method of a coreless package substrate, characterized by, Comprising: providing a support plate comprising a substrate, a first copper foil attached to both sides of the substrate, a second copper foil attached to the first copper foil; pressing a first prepreg and a third copper foil on the second copper foil; performing a graphic making on the third copper foil to form a circuit pattern; pressing a second prepreg and a fourth copper foil on the third copper foil, wherein the thickness of the second prepreg is different from the thickness of the first prepreg, so that the thickness of a second dielectric layer formed by curing the second prepreg is the same as the thickness of a first dielectric layer formed by curing the first prepreg; separating the first copper foil from the second copper foil to obtain two coreless packaging substrates comprising a second copper foil, a first prepreg, a third copper foil, a second prepreg, and a fourth copper foil stacked in sequence.

2. The processing method of claim 1, wherein: before pressing the first prepreg and the third copper foil on the second copper foil, further comprising: performing a first drilling to form a plurality of first through holes penetrating from one side of the second copper foil to the other side of the second copper foil; after pressing the first prepreg and the third copper foil on the second copper foil, further comprising: performing a second drilling to form a plurality of second through holes penetrating from one side of the third copper foil to the other side of the third copper foil.

3. The method of claim 2, wherein, The thickness of the first dielectric layer is calculated according to the following formula: Te1 = Ta - 3.14 * (D1 / 2)2 * N1 * t / S wherein Te1 is the thickness of the first dielectric layer, Ta is the thickness of the first prepreg, D1 is the hole diameter of the first through hole, N1 is the number of the first through hole, t is the thickness of the coreless packaging substrate, and S is the area of the coreless packaging substrate.

4. The method of claim 3, wherein The thickness of the second dielectric layer is calculated according to the following formula: Te2 = Tb - 3.14 * (D2 / 2)2 * N2 * t / S - Tc * (1 - c%) wherein Te2 is the thickness of the second dielectric layer, Tb is the thickness of the second prepreg, D2 is the hole diameter of the second through hole, N2 is the number of the second through hole, Tc is the thickness of the third copper foil, and c% is the residual copper rate of the third copper foil after forming the circuit pattern.

5. The method of processing according to any one of claims 1 to 4, wherein, The pressing condition of pressing the first prepreg and the third copper foil on the second copper foil is different from the pressing condition of pressing the second prepreg and the fourth copper foil on the third copper foil, so that the resin overflow amount of the first prepreg is greater than the resin overflow amount of the second prepreg.

6. The method of claim 5, wherein, The heating rate when pressing the first prepreg and the third copper foil on the second copper foil is less than the heating rate when pressing the second prepreg and the fourth copper foil on the third copper foil, so as to prolong the melt flow time of the first prepreg.

7. The method of claim 5, wherein, The high pressure temperature when pressing the first prepreg and the third copper foil on the second copper foil is lower than the high pressure temperature when pressing the second prepreg and the fourth copper foil on the third copper foil, so as to accelerate the resin flowability of the first prepreg.

8. The method of claim 5, wherein, The maximum pressure when pressing the first prepreg and the third copper foil on the second copper foil is greater than the maximum pressure when pressing the second prepreg and the fourth copper foil on the third copper foil, so as to accelerate the resin flowability of the first prepreg.

9. The method of processing according to any one of claims 1 to 4, wherein, The roughness of the second copper foil is greater than the roughness of the fourth copper foil, so that the first prepreg fills the second copper foil to a greater extent than the second prepreg fills the fourth copper foil.

10. A coreless package substrate, characterized by, The coreless packaging substrate is prepared by the processing method of any one of claims 1 to 9.

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