CN1875669A - Printed circuit board including track gap-filled resin and fabricating method thereof - Google Patents

Abstract

The present invention relates to a printed circuit board (PCB) including a track gap-filled resin (TGFR). In the inventive PCB, a new resin TGFR having a special composition is filled in a track gap, so that delamination is prevented to improve the electrical insulation and dielectric strength between tracks. Also, since the track gap on the dielectric layer is filled with the TGFR, a product where the thickness of a dielectric layer is smaller than that of the track can be produced. Furthermore, as the synthetic resin TGFR is used, the PCBs or electrical components mounted thereon show an excellent cooling effect in their operation, and also have excellent reliability against their use environments (heat, humidity and insulation). In addition, as the TGFR is filled in the cavity of the track gap, the inventive PCB shows low flexibility, so that inferior rate in a process of mounting and assembling components on the PCB is significantly reduced. Also, the TGFR prevents a portion of the copper foil at the wall of the conductor pad from being exposed to the external environment, so that a short-circuit phenomenon in the mounting and soldering of components on the PCB can be prevented.

Description

Printed circuit board with trace gap filling resin and manufacturing method thereof

technical field

The present invention relates to a printed circuit board (PCB), in particular to a printed circuit board with trace gap filling resin (TGFR) (hereinafter referred to as TGFR PCB) and a manufacturing method thereof, wherein the TGFR with a special composition is applied After being formed in the wiring gap on the PCB and flattened, the electrical insulation and dielectric strength between the wiring can be improved and the short circuit phenomenon that occurs when installing and soldering electronic components on the PCB is prevented.

Background technique

Generally, a PCB is a thin plate on which electronic components such as integrated circuits, resistors, and switches are soldered. When manufacturing a PCB, copper foil is attached to a thin plate made of an electrical insulating resin such as epoxy or phenolic plastic, and then a resist is applied to a portion of the copper foil that is used for circuit interconnection. Then, the resist-coated board was immersed in an etching solution capable of corroding copper, and the portion of the copper foil not coated with the resist was corroded. Then, when the resist is removed, the desired circuit layout of the copper foil remains on the board. Holes are drilled on the part of the copper foil with circuit layout that needs to be installed with electronic components, and other parts of the copper foil are covered with blue solder resist for preventing corrosion by solder.

FIG. 1 is a schematic cross-sectional view of an existing PCB structure. As shown in FIG. 1 , the middle part of an existing PCB is a dielectric layer 1 . On each outer surface of the dielectric layer 1, a conductive pad 2 and a wire 3 are formed. A trace gap 6 of a specific width is formed between the conductive pad 2 and the trace 3 . On the conductive pad 2 and the trace 3, there is a given pattern formed by a solder mask 4 or a surface finish 5.

The dielectric layer 1 is also called "prepreg material", which is obtained by heat-treating a reinforced cloth made of paper or glass fiber for PCB, and then treating its surface with a silane bonding agent And coated with various resins (or soaked in resin).

The prepreg is laminated with copper foil and pressed to form a copper foil laminated dielectric board. Multiple dielectric plates are stacked on top of each other and subjected to sufficient heat and pressure treatment. In this lamination process, a layer of copper foil is bonded to one or both laminate surfaces.

Then, the portion of the copper foil that will be used for the circuit is coated with ink or dry film resist, and the portion that is not coated with resist is etched. Holes are drilled in the portion of copper foil remaining after the etching process and plated with metal for connection. Then, various electronic components are soldered in place on the copper foil layer. In some cases, electronic components can also be attached to the copper foil layer using epoxy glue.

Therefore, according to the PCB manufacturing process of the prior art, it is impossible to produce a product in which the thickness of the dielectric layer 1 is smaller than that of the traces. Also, existing PCBs are significantly affected by usage environments such as heat, humidity, and insulation. For example, when its cooling effect is reduced, existing PCBs may experience delimitation due to temperature rise. Moreover, when the existing PCB is mounted with electronic components and operated, product reliability will be reduced due to heat generated by the PCB itself or the electronic components. In addition, due to the high flexibility of the existing PCB due to the wiring gap 6 , many defective products will be produced when installing and assembling electronic components on the PCB.

In particular, in the case of a thick copper PCB, the copper foil constituting the conductive pad 2 is exposed to the external environment during soldering, which may cause a short circuit phenomenon. Also, since the impregnation of the resin may not be complete, the dielectric layer 1 must use a greater thickness.

Contents of the invention

Therefore, the present invention serves to overcome the above-mentioned prior art problems, and an object of the present invention is to provide a printed circuit board (PCB) with trace gap filling resin (TGFR), the manufacturing method of which comprises the steps of: Etching and surface cleaning; oxidation or micro-etching treatment on the surface and wall of the trace; filling TGER in the trace gap; curing and flattening the filled TGFR to complete the PCB filled with TGFR in the trace gap.

And, the present invention provides a kind of manufacturing method of multi-layer thick copper PCB board, comprise: the step in the above-mentioned object; Carry out the step of oxidizing inner layer circuit, cladding and lamination; Carry out surface cleaning with outer layer circuit, Steps of coating PSF and drying, exposing, developing, PSR curing and screen printing.

Description of drawings

FIG. 1 is a schematic cross-sectional view of an existing PCB structure.

Fig. 2 is a schematic cross-sectional view of the TGFR PCB structure involved in the present invention.

Fig. 3 is a schematic cross-sectional view of multiple stacked TGFR PCBs involved in the present invention.

Fig. 4 is a schematic flow chart of the manufacturing process of the TGFR PCB involved in the present invention.

Detailed ways

The following is a detailed description of the present invention with reference to the accompanying drawings, wherein, Fig. 2 is a schematic cross-sectional view of a TGFR PCB structure involved in the present invention; Fig. 3 is a schematic cross-sectional view of a plurality of TGPR PCBs involved in the present invention stacked; Fig. 4 is a schematic cross-sectional view of this invention Schematic diagram of the manufacturing process of the TGFR PCB involved in the invention.

As shown in Figure 2, the TGPR PCB involved in the present invention has a dielectric layer 1 in the middle part. On each outer surface of the dielectric layer 1 , conductive pads 2 and traces 3 are formed, and trace gap filling resin (TGFR) 10 is filled between the conductive pads 2 and the traces 3 . On the conductive pad 2 and the trace 3, there is a given pattern formed by a solder mask 4 or a surface finish 5.

TGFR10 is a new synthetic resin with a composition that enhances insulation and dielectric strength between traces. In one embodiment of the present invention, TGFR preferably comprises 18-23wt% of DGEBPA (diglycidyl ether of bisphenol A), 3-7wt% of modified epoxy resin, 27-33wt% of DBDO , 3-7wt% antimony trioxide, 30-35wt% aluminum hydroxide and 3-7wt% dicyandiamide.

In another embodiment, TGFR10 preferably includes 5-10wt% modified epoxy resin, 40-50wt% aluminum hydroxide, 20-30wt% mineral water, and about 10wt% flame retardant, Hardeners and pigments. This formula has excellent heat dissipation effect.

The solder resist layer 4 is a part of the PCB, and it is used to apply ink on the PCB to prevent solder from adhering to parts of the PCB where the component mounting layer should not be attached and to keep the surface circuit of the PCB from contacting the external environment. It is also known as "solder mask" or "solder mask". In the present invention, for the convenience of description, the part covered with ink refers to the solder resist layer 4 .

The solder resist layer 4 can be produced by a process appropriately selected according to the use environment and conditions. Examples of such processes include: Photosolder Resist (PSR) processes, where inks with a viscosity of 150-300 poises are applied over the entire substrate with circuitry, exposed and developed; Liquid Photoimaging (LPI) Exactly the same but using inks with a viscosity less than 100 poise; and Infrared (IR), masking and carbon treatment process is to apply ink on the surface of the substrate through a screen and print without exposure. In one embodiment of the present invention, the solder resist layer 4 is obtained through a PSR process.

In addition, in the present invention, the location of the solder resist layer 4 is higher than the surface coating layer 5 on the conductive pad 2, thus improving the electrical insulation between the traces and preventing the occurrence of a short circuit due to the exposure of the copper foil to the external environment. Phenomenon.

At the same time, TGFR PCB can also form a multi-layer structure. In one embodiment of the present invention, shown in FIG. 3 , is a multi-layer thick copper PCB with a three-layer structure.

As shown in FIG. 3 , the upper part of the multilayer thick copper PCB involved in the present invention has an upper dielectric layer 1 . An outer circuit 12 is formed on the upper surface of the dielectric layer 1 , including a conductive pad 2 , a trace 3 , and a TGFR 10 filling the trace gap between the conductive pad 2 and the trace 3 . On the conductive pad 2 and the wiring 3 , there is a given pattern formed by the solder resist layer 4 or the surface coating layer 5 .

In addition, on the lower surface of the dielectric layer 1 , there is an inner circuit 11 composed of conductive pads 2 , traces 3 , and TGFR 10 filling the trace gap between the conductive pads 2 and the traces 3 .

The inner layer wiring 11 is oxidized to enhance its adhesion to the dielectric layer 1 located in the middle of the lower surface of the inner layer wiring 11 . Then, the inner layer wiring 11 is tightly adhered to the intermediate dielectric layer 1 .

On the lower surface of the dielectric layer 11 in the middle, there is an inner layer circuit 11 composed of a conductive pad 2, a wiring 3, and a TGFR 10 filling the wiring gap between the conductive pad 2 and the wiring 3. On the lower surface of the inner layer circuit 11, a lower dielectric layer 11 is attached.

On the lower surface of the lower dielectric layer 1 is an outer circuit 12 composed of conductive pads 2 , traces 3 , and TGFR 10 filling the trace gap between the conductive pads 2 and the traces 3 . On the conductive pad 2 and the wiring 3 , there is a given pattern formed by the solder resist layer 4 or the surface coating layer 5 .

According to the above description, by placing the dielectric layer 1 between the inner layer lines 11 of single-layer TGFR PCBs, a multi-layer thick copper PCB can be easily fabricated.

Each step of the TGFR PCB manufacturing method involved in the present invention will be described below with reference to the flow chart FIG. 4 .

According to the circuit design diagram, first drill some required holes on the PCB board through the drilling step S1. In order to form a circuit connection on the PCB, chemical and electrolytic copper plating step S2 is then performed on the PCB.

Etching step S3 and step S4 are performed on the copper-plated PCB to form a trace gap 6 with a given width.

Step S5 is mainly to clean the surface of the PCB substrate already having the wiring gap 6 to remove impurities. In the surface treatment step, micro-etching and/or oxidation treatment is used to treat the surface and inner wall of the wiring gap.

After the surface cleaning step S5 is completed, step S6 is to apply the wiring gap filling resin 10 to the wiring gap 6 . TGFR10 is coated by printing or roller coating, and then cured quickly by an external hot air blower or heater.

After TCFR10 is cured, step S7 is to smooth the surface of TGFR by grinding, brushing, cutting or their combination.

The subsequent steps are to perform different treatments on the inner layer circuit 11 and the outer layer circuit 12 respectively.

For the inner circuit 11 , step S11 is to oxidize the surface of the inner circuit to enhance the adhesion between the resin forming the dielectric layer 1 and the inner circuit 11 . Then, the cladding step S12 and the lamination step S13 are sequentially performed. Subsequent steps are the same as the usual process of manufacturing a multi-layer PCB board, so these descriptions are omitted here.

For the outer circuit 12, the surface cleaning step S21 is performed before coating the PSR. In the surface cleaning step S21 , microetching and/or oxidation treatment is performed on the surface and inner wall of the wiring gap.

To the surface of the PCB board after the surface cleaning step S21 is carried out, the step S22 of coating and drying photo-solder resist (PSR), the step S23 of exposure, the step S24 of developing, the step S25 of PSR curing and the step S26 of screen printing are carried out successively. These and subsequent steps are the same as the usual process of manufacturing multi-layer PCB boards, so these descriptions are omitted here.

Although the above is a description of preferred embodiments of the present invention for illustrative purposes, it will be appreciated that those skilled in the art can make various modifications and changes to the present invention. However, these modifications and changes should not go beyond the protection scope of the present invention.

Industrial applicability

As mentioned above, in the TGFR PCB involved in the present invention, a new resin TGFR with a special composition is filled in the trace gap 6, so delamination can be prevented, thereby improving the electrical insulation and dielectric between traces strength. In addition, since the trace gap 6 on the dielectric layer 1 is filled with TGFR, it is possible to produce a product in which the thickness of the dielectric layer 1 is smaller than that of the trace. In addition, due to the use of synthetic resin, the PCB or electronic components mounted thereon have an excellent cooling effect during operation and excellent reliability against their usage environment (heat, humidity, and insulation).

In addition, since the trace gap 6 is filled with TGFR10, the PCB involved in the present invention is flexible, so the occurrence rate of defects when installing and assembling components on the PCB board is significantly reduced. Moreover, the TGFR10 can prevent the copper foil on the wall of the conductive pad 2 from being exposed to the external environment, and thus can prevent short circuits when mounting and soldering components on the PCB.

Claims (6)

1. A printed circuit board (PCB) with trace gap filling resin (TGFR), comprising a dielectric layer (1), conductive pads (2) and traces (3) formed on each side of the dielectric layer (1) ), and a trace gap (6) of a given width formed between the conductive pad (2) and the trace (3), Among them, the trace gap (6) is filled with trace gap filling resin (TGFR) (10) to enhance insulation and dielectric strength, and the solder resist layer (3) formed on the trace (3) and TGFR (10) is more than The position of the surface coating layer (5) formed on the conductive pad (2) is high. 2. The PCB according to claim 1, wherein the TGFR (10) comprises 18-23wt% of DGEBPA (diglycidyl ether of bisphenol A), 3-7wt% of modified epoxy resin, 27-33wt% % DBDO, 3-7 wt% antimony trioxide, 30-35 wt% aluminum hydroxide, and 3-7 wt% dicyandiamide. 3. The PCB according to claim 1, wherein the TGFR (10) comprises 5-10wt% modified epoxy resin, 40-50wt% aluminum hydroxide, 20-30wt% mineral water, and about 10wt% Flame retardants, curing agents and pigments. 4. A method of manufacturing a PCB with TGFR, comprising: The drilling step (S1) is to form the required holes on the PCB; The chemical and electroplating copper step (S2) is to form an electrical connection on the PCB; The etching steps (S3) and (S4) are to form a trace gap (6) on the copper-plated PCB. The surface cleaning step (S5) is to remove impurities on the PCB board where the trace gap (6) has been formed; The coating and curing step (S6) is to fill the trace gap filling resin (TGFR) (10) in the trace gap (6); The TGFR surface smoothing step (S7) is to smooth the surface of the solidified TGFR by grinding, brushing, cutting or their combination; Oxidation treatment step (S11) for enhancing adhesion of inner layer circuit (11) to resin forming dielectric layer (1), cladding step (S12) and lamination step (S13) carried out sequentially on inner layer circuit (11) );and Surface cleaning step (S21), photo solder resist (PSR) coating and drying step (S22), exposure step (S23), development step (S24), PSR curing step (S25) carried out in sequence on the outer layer circuit (12) and a screen printing step (S26). 5. The method according to claim 4, wherein said surface treatment steps (S5) and (S21) use microetching or oxidation treatment. 6. The method according to claim 4, wherein, in the TGFR coating and curing step (S6), the coating is done by printing or roll coating, and the coated TGFR (10) is passed through an external hot air blower or heaters that cure quickly.