CN115119411A

CN115119411A - Packaging body steel mesh-free printing welding method and prefabricated substrate

Info

Publication number: CN115119411A
Application number: CN202210874319.1A
Authority: CN
Inventors: 张光耀
Original assignee: Hefei Silicon Microelectronics Technology Co ltd
Current assignee: Hefei Silicon Microelectronics Technology Co ltd
Priority date: 2022-07-25
Filing date: 2022-07-25
Publication date: 2022-09-27

Abstract

The invention discloses a package body steel mesh-free printing welding method and a prefabricated substrate, and the method comprises the following steps: providing a carrier plate; step two: prefabricating a circuit and an insulating layer on the surface of the carrier plate; step three: electroplating a bonding pad electrically communicated with the prefabricated line on the insulating layer, and grinding one side of the bonding pad, which is far away from the carrier plate, after packaging, wherein the grinding roughness range is 200-500 meshes so as to facilitate the movement of a printing scraper; step four: fully etching the pad to form a pit, and storing the pit for later use after an anti-oxidation layer is formed on the pit; step five: the printing machine is used for printing solder on the pits, the chip is reversely mounted with the patch and then is welded and fixed, and finally the carrier plate is peeled.

Description

Packaging body steel mesh-free printing welding method and prefabricated substrate

Technical Field

The invention belongs to the technical field of package welding, and particularly relates to a package steel mesh-free printing welding method and a prefabricated substrate.

Background

In the semiconductor packaging industry in recent years, various packaging methods are developed, and advantages such as higher density, stronger function, more careless performance, smaller volume, lower power consumption and the like are achieved, a chip needs to be mounted on a substrate or a circuit board (PCB) in the packaging process, a common mounting method is solder paste soldering, and a solder paste printer is generally adopted when a plurality of packaging factories print solder paste on the substrate or the circuit board.

The modern solder paste printer generally comprises mechanisms such as a plate loading mechanism, a solder paste adding mechanism, an imprinting mechanism and a power transmission circuit board, and mainly comprises a vision positioning system, a wiping system, a solder paste filling system and the like, and the working principle of the modern solder paste printer is as follows: the method comprises the steps of firstly designing a corresponding steel mesh according to a chip welding position, fixing a circuit board or a substrate to be printed on a printing positioning table, placing the steel mesh on the surface of the substrate or the circuit board, and then carrying out screen printing on solder paste on the PCB or the substrate through the steel mesh by a left scraper and a right scraper of a printing machine to form corresponding bonding pads, and inputting the solder paste to a chip mounter through a transmission table to automatically mount the solder paste on the PCB or the substrate with uniform screen printing.

The printing quality of the solder paste has great influence on the electrical property of the circuit, and the influence factors of the printing quality are more, wherein the main surface is the equipment precision on two aspects: the solder paste printer is used as the only printing equipment, the precision is critical, the printer positions the hole position of the upper bonding pad of the to-be-printed board through the visual positioning system, when a high-precision fine-pitch product is printed, the visual positioning system is low in precision, the situations of missing soldering, repeated soldering or uneven solder filling are easy to occur, bridging is caused by too much solder, and insufficient solder causes false soldering; on the other hand, the steel mesh quality: the steel mesh can scribble the one deck solder mask at completion design rear surface, ensure that the solder drops into in the pad, consume the solder mask, the thickness of steel mesh needs to customize according to different production requirements, the cost is higher, and can't grind, the thickness flexibility is less, the steel mesh needs to design the small opening according to actual production's chip customization, belong to the consumable items, the cost is increased, and the steel mesh must be sanitized just can use after finishing using, consuming time and consuming power, the problem that the trompil itself also has the yield on the steel mesh, the steel mesh takes place the skew easily and influences the printing quality, 75% the main problem of the above circuit board reprocess is the printing tin cream quality problems that the steel mesh harmfully leads to, how to save the steel mesh, low cost, high qualification rate, the welding tin cream of high accuracy, guarantee that circuit connection becomes each encapsulation factory awaits the technological problem of solving.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a package body welding method without steel mesh printing and a prefabricated substrate.

In order to achieve the above object, the present invention provides a method for welding a package without steel mesh printing, comprising the following steps:

the method comprises the following steps: providing a carrier plate;

step two: prefabricating a circuit and an insulating layer on the surface of the carrier plate;

step three: electroplating a bonding pad electrically communicated with the prefabricated line on the insulating layer, and grinding one side of the bonding pad, which is far away from the carrier plate, after packaging, wherein the grinding roughness range is 200-500 meshes so as to facilitate the movement of a printing scraper;

step four: fully etching the pad to form a pit, and storing the pit for later use after an anti-oxidation layer is formed on the pit;

step five: and printing solder on the pits by using a printer, inversely mounting the chip on the surface, welding and fixing, and finally stripping the carrier plate.

Furthermore, the prefabricated line comprises a conducting layer and a rewiring layer, the insulating layer is made of epoxy resin plastic package materials, the insulating layer encapsulates the prefabricated line and the pit, and the upper surface of the insulating layer is flush with the upper end of the pit.

Furthermore, the bonding pad is formed in an electroplating mode, and the diameter or the width of an effective welding spot of the bonding pad is larger than or equal to 15 microns so as to ensure the flip chip bonding of the chip.

Furthermore, the pad is etched by a wet method, and the depth range of the pits is more than or equal to 25 mu m.

Further, the anti-oxidation layer is a gold-plating layer or an ethylene bis-oleic acid amide adhesive layer or an organic solderability preservative film layer.

Furthermore, the carrier plate is peeled off physically.

A prefabricated substrate comprises a carrier plate, wherein a prefabricated line and an insulating layer are arranged on the surface of the carrier plate, a bonding pad is formed on the surface of the insulating layer, the bonding pad is exposed in an enveloping and grinding mode, one side of the bonding pad, far away from the carrier plate, is convenient to move of a printing scraper due to the fact that the roughness range of the grinding is 200-500 meshes, pits are formed by etching the bonding pad, and an anti-oxidation layer is arranged at the pits.

Has the advantages that: 1. the original shallow bonding pad formed on the substrate is changed into the pit formed in the insulating layer, the surface of the insulating layer can be used as a movable surface of the scraper after being ground, the grinding height and the roughness are controllable, the printing requirement is met, the height of the insulating layer and the depth of the pit are controllable, the height of a scraping surface is increased without additionally using a steel mesh, the consumable product of the steel mesh is omitted, the cost is saved, the printing mechanism of the printing machine is simplified, the steel mesh mechanism is omitted, and the equipment cost and the maintenance cost are reduced;

2. after the steel mesh is saved, the printing influence caused by steel mesh deviation is avoided, the sizes of the steel mesh and the substrate of the traditional printing machine need to be matched with each other, the influence factors are the substrate, the steel mesh and the matching degree between the substrate and the steel mesh, the size is moderate, the cost is directly influenced by overlarge and undersize, the efficiency is influenced by improving the accuracy when the undersize is too small, the efficiency is improved by improving the accuracy when the oversize is too large, and the yield of the large-sized steel mesh openings cannot be controlled, the cost is high and the risk is high, but the application directly prints on the packaging body, the influence factors are only the substrate, but the parameters of the substrate such as height and surface roughness are controllable, so that the printing requirements are met, the most common glass epoxy resin organic plate in the field is adopted, the quantity is large, the materials are conveniently obtained, and the price is low, so that the method is suitable for high-precision printing of large-size substrates, and the problems of printing offset and inaccurate position caused by large-size offset are avoided;

3. the prefabricated substrate can be suitable for steel mesh-free printing equipment during printing, the cost is saved, the production efficiency can be increased by the prefabricated substrate, the prefabricated substrate is formed in a large batch and then put in storage for later use, and subsequent direct surface mounting encapsulation, stripping and cutting are performed.

Drawings

FIG. 1 is a schematic diagram of a steel mesh structure of a conventional solder paste printer;

FIG. 2 is a process flow chart of a method for soldering a package without steel mesh printing according to the present invention;

FIG. 3 is a schematic structural diagram of a prefabricated circuit of a package body in a soldering method without steel mesh printing according to the present invention;

FIG. 4 is a schematic structural diagram of a bonding pad of a package body in a soldering method without steel mesh printing according to the present invention;

FIG. 5 is a schematic structural diagram of a pad encapsulation of a package without a stencil printing and soldering method according to the present invention;

FIG. 6 is a schematic diagram illustrating a pad etching structure of a package body soldering method without stencil printing according to the present invention;

FIG. 7 is a schematic structural diagram of a prefabricated substrate for soldering without stencil printing of a package according to the present invention;

FIG. 8 is a schematic view of a printing solder paste of a package soldering method without steel mesh printing according to the present invention;

FIG. 9 is a schematic structural diagram of a flip chip of a package without a steel mesh printing and soldering method according to the present invention;

fig. 10 is a schematic structural diagram of a BGA chip mounting method for a package without steel screen printing and soldering method according to the present invention.

The notation in the figure is: the circuit comprises a carrier plate 1, an insulating layer 2, a prefabricated circuit 3, a bonding pad 4, a pit 5 and an anti-oxidation layer 6.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

For better understanding of the purpose, structure and function of the present invention, a package soldering method without stencil and a prefabricated substrate according to the present invention will be described in detail with reference to fig. 1 to 10.

The present invention relates to a method for welding a package without steel mesh printing, and fig. 2 is a process flow diagram of the method for welding the package without steel mesh printing, and referring to fig. 1, the method of the present invention comprises the following steps: the method comprises the following steps: providing a carrier plate 1; step two: prefabricating a circuit 3 and an insulating layer 2 on the surface of a carrier plate 1; step three: plating a bonding pad 4 electrically communicated with the prefabricated circuit 3 on the insulating layer 2, and grinding the side, away from the carrier plate 1, of the bonding pad 4 after encapsulation, wherein the grinding roughness range is 200-500 meshes so as to facilitate the movement of a printing scraper; step four: the pad 4 is etched completely to form a pit 5, and an oxidation-resistant layer 6 is formed at the pit 5 and then is put in storage for standby; step five: and printing solder on the pit 5 by using a printer, inversely mounting the chip on the chip, welding and fixing, and finally peeling the carrier plate 1.

Referring to fig. 2 and 3, step one and step two, a carrier board 1 is provided, a circuit 3 and an insulating layer 2 are preformed on a surface of the carrier board 1, the carrier board 1 is a glass epoxy resin organic PCB raw material board commonly used in the art, such as an FR-4 substrate, the preformed circuit 3 is an encapsulating layer, specifically, an epoxy resin encapsulating layer commonly used in the art, the preformed circuit 3 includes a conductive layer and a redistribution layer, the conductive layer is formed on the carrier board 1 by an electroplating process, then the circuit is wired by the electroplating process according to a production condition to form the redistribution layer, then the preformed circuit 3 is encapsulated by a plastic encapsulating material, and the top of the preformed circuit 3 is exposed by grinding, at this time, the top of the preformed circuit 3 is flush with the insulating layer 2.

Referring to fig. 2, fig. 4, fig. 5 and step three, a bonding pad 4 is formed on the upper surface of the insulating layer 2 by electroplating, an effective welding spot of the bonding pad 4 is larger than or equal to 15 μm to ensure normal flip chip mounting of a subsequent chip, the bonding pad 4 is encapsulated by using the same material in the step two, and one surface of the bonding pad 4, which is far away from the carrier plate 1, is ground, at this time, the top of the bonding pad 4 is flush with the insulating layer 2, and the ground roughness range is 200-500 meshes so as to facilitate the movement of a printing scraper, in the application, for example, 300 meshes are used, the smoothness of the scraper with too small roughness is higher, the speed control of the scraper needs to be more accurate, otherwise, the situation of few welding is easy to occur, the smoothness of the scraper with too large roughness is lower, and a coarse surface is easy to remain tin paste, which causes waste.

Referring to fig. 2, fig. 6, fig. 7 and step four, the pad 4 is completely etched by a wet etching method commonly used in the art, and the concentration of an etching line, etching time and other parameters are controlled to ensure that the pad 4 is completely etched and the preformed line 3 is not etched, because the lower end of the pad 4 is electrically connected with the upper end of the preformed line 3, the preformed line 3 is partially exposed after the pit 5 is formed by etching the pad 4, and the exposed preformed line 3 is provided with an anti-oxidation layer 6, specifically a gold plating layer or an ethylene bis-oleamide glue layer or an organic solder mask layer, which are common processing methods in the art, at this time, the upper surface of the insulating layer 2 is flush with the upper end of the pit 5, the insulating layer 2 includes two encapsulating layers of the whole substrate manufacturing process flow of the present application, and the prepared substrate can be put in storage for use.

Referring to the attached

drawings

2, 6, 7, 8 and the fifth step, the inventory is taken, the prefabricated substrate is integrally placed in a printer, the insulating layer 2 has controllable height, the pits 5 have controllable depth, the insulating layer 2 replaces a steel mesh, a scraper directly scrapes solder mass or soldering flux on the surface of the insulating layer 2, the soldering flux is used for preprocessing a welding part, the welding effect is enhanced, the soldering flux is volatilized during welding, the structure of the printer is simplified according to actual production decision, the steel mesh which is an easily-consumed product is removed, and the equipment cost is reduced.

Referring to fig. 9 and 10, the pre-fabricated substrate is suitable for mounting a chip package with protruding leads, such as BGA package, i.e. ball grid array package, flip-chip package, i.e. chip type in which the chip pins are mounted toward the substrate, the chip can be power type, antenna type, oscilloscope type, etc., ball-mounting package refers to mounting matrix-arranged solder balls as outer pins on the inner pins of the package, flip-chip package refers to plating conductive copper posts as outer pins on the inner pins of the package, one end of the conductive copper column is plated with tin, the embedded ball and the tin cream in the pit 5 are synthesized into a large tin ball during welding, the conductive copper column is welded with the tin cream through the tin, the reflow soldering commonly used in the field is adopted in the application, the reflow soldering refers to that air or nitrogen is heated to a high enough temperature and then blown to the substrate on which the element is stuck, and the element is bonded with the substrate after the solder is melted.

FIG. 1 is a schematic structural diagram of a steel mesh of a conventional solder paste printer, and please refer to FIG. 1. the working principle of the conventional printer is mainly that a circuit board or a substrate to be printed is fixed on a printing positioning table, pads are prefabricated on the surface of the circuit board or the substrate, the pads have indefinite shapes, and can be round or square, and are determined according to actual production, the steel mesh is placed on the surface of the substrate or the circuit board, then solder paste is printed on the corresponding pads on the PCB or the substrate through the steel mesh by left and right scrapers of the printer, the PCB or the substrate with uniform missing printing is input into a chip mounter through a transmission table for automatic chip mounting, a chip is mounted on the substrate for using the substrate as an intermediate carrier plate, the chip is wired or encapsulated after forming electrical connection on the substrate, and finally the intermediate is peeled off in a physical manner, in order to ensure that the depth of a bonding pad on the substrate is shallow, and a large-depth bonding pad can not complete the stripping action, so that the welding part of the chip and the bonding pad is easy to break, and the subsequent packaging and circuit connection are influenced, therefore, the condition that a large-depth bonding pad is etched on the substrate to save a steel mesh does not exist; the chip is pasted on the PCB board in order to paste the chip and the components on the circuit board to realize the electric connection between each component, the circuit board surface is etched with the circuit diagram, there is one deck or multilayer circuit connection inside the circuit board, even there is component to paste on the PCB board two-sided all, for not influencing inside circuit connection and two-sided subsides, the circuit diagram etching depth on its surface is shallower, guarantee that the welding pastes the dress fixed can, so also do not exist and etch out the condition that big degree of depth pad saved the steel mesh on the PCB board.

In summary, compared with the prior art, the present application has the following advantages:

1. the original shallow-mouth pad formed on the substrate is changed into the pit 5 formed in the insulating layer 2, the surface of the insulating layer 2 can be used as a movable surface of a scraper after being ground, the grinding height and roughness are controllable, the printing requirement is met, the height of the insulating layer 2 and the depth of the pit 5 are controllable, the height of a scraping surface is not required to be increased by additionally using a steel mesh, the easily-consumed product of the steel mesh is omitted, the cost is saved, the printing mechanism of a printing machine is simplified, no steel mesh mechanism is provided, and the equipment cost and the maintenance cost are reduced;

2. after the steel mesh is saved, the printing influence caused by steel mesh deviation is avoided, the sizes of the steel mesh and the substrate of the traditional printing machine need to be matched with each other, the influence factors are the substrate, the steel mesh and the matching degree between the substrate and the steel mesh, the size is moderate, the cost is directly influenced by over-large and over-small sizes, the efficiency is influenced by improving the accuracy when the accuracy is over-small, the efficiency is improved by influencing the accuracy when the accuracy is over-large, and the yield of the large-sized steel mesh openings cannot be controlled, the cost is high and the risk is high, but the application directly prints on the packaging body, the influence factors are only the substrate, but the parameters of the substrate, such as height and surface roughness, are controllable, so that the printing requirements are met, the most commonly used glass epoxy resin organic plate in the field is adopted, the quantity is large, the materials are conveniently obtained, and the price is low, so that the method is suitable for high-precision printing of large-size substrates, and the problems of printing offset and inaccurate position caused by large-size offset are solved;

It is to be understood that the present application is described with respect to certain embodiments, and it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present application. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its spirit or scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A package body steel mesh-free printing welding method comprises the following steps: the method comprises the following steps: providing a carrier (1); the method is characterized by comprising the following steps: prefabricating a circuit (3) and an insulating layer (2) on the surface of a carrier plate (1); step three: electroplating a bonding pad (4) which is electrically communicated with the prefabricated circuit (3) on the insulating layer (2), grinding the side, away from the carrier plate (1), of the bonding pad (4) after encapsulation, wherein the grinding roughness range is 200-500 meshes so as to facilitate the movement of a printing scraper; step four: fully etching the bonding pad (4) to form a pit (5), forming an anti-oxidation layer (6) at the pit (5), and storing for later use; step five: and printing solder on the pit (5) by using a printer, inversely mounting the chip, welding and fixing the chip after the chip is pasted, and finally peeling the carrier plate (1).

2. The package body steel-net-free printing and welding method according to claim 1, wherein the preformed line (3) comprises a conductive layer and a rewiring layer, the insulating layer (2) is epoxy resin molding compound, the insulating layer (2) encapsulates the preformed line (3) and the pit (5), and the upper surface of the insulating layer (2) is flush with the upper end of the pit (5).

3. The package body steel-net-free printing and welding method according to claim 2, wherein the bonding pads (4) are formed by electroplating, and the effective welding spot diameter or width of the bonding pads (4) is larger than or equal to 15 μm so as to ensure flip chip bonding of the chip.

4. The package body steel-net-free printing and welding method according to claim 3, wherein the bonding pads (4) are wet-etched, and the depth range of the pits (5) is more than or equal to 25 μm.

5. The package body steel-net-free printing welding method according to claim 4, wherein the oxidation preventing layer (6) is a gold plating layer or an ethylene bis-oleic acid amide glue layer or an organic solderability preservative layer.

6. The package body soldering method without steel mesh printing according to claim 5, wherein the carrier (1) is peeled off physically.

7. The prefabricated substrate comprises a carrier plate (1) and is characterized in that a prefabricated line (3) and an insulating layer (2) are arranged on the surface of the carrier plate (1), a bonding pad (4) is formed on the surface of the insulating layer (2), one side, far away from the carrier plate (1), of the bonding pad (4) is exposed through encapsulation grinding, the grinding roughness range is 200-500 meshes so as to facilitate the movement of a printing scraper, a pit (5) is formed by etching the bonding pad (4), and an anti-oxidation layer (6) is arranged at the pit (5).

8. The pre-encapsulated substrate according to claim 7, wherein the oxidation protection layer (6) is a gold plating layer or an ethylene bis-oleic acid amide glue layer or an organic solderability preservative film layer.