CN111315151A

CN111315151A - Processing technology of leadless plug electrogilding and plate surface gilding printed circuit board

Info

Publication number: CN111315151A
Application number: CN202010251914.0A
Authority: CN
Inventors: 倪蕴之; 朱永乐; 杨存杰
Original assignee: Jiang Suhang Electronic Co ltd
Current assignee: Jiang Suhang Electronic Co ltd
Priority date: 2020-04-01
Filing date: 2020-04-01
Publication date: 2020-06-19

Abstract

The invention discloses a processing technology of leadless plug electrogilding and plate surface gilding printed circuit board, when a circuit pattern of the circuit board is manufactured, a process lead is arranged, and a gilding plug which is used as an external connecting channel is connected together to form a same conductive network; when the solder mask protection pattern is manufactured, all the welding pads needing to be welded, the welding pads pasted by the SMT, the gold-plated plugs and the process leads connected with the gold-plated plugs are exposed, and all the connecting circuit patterns and the wire through holes are covered by the solder mask layer. The invention meets the requirements of two different gold plating thicknesses on different parts of the same surface of a printed circuit board, thereby not only meeting the requirements of surface mounting and welding of electronic components such as BGA, QFP and the like, but also ensuring the good weldability of the surface of the welding pad. But also can ensure that the thickness of the gold-plating layer at the position of the gold-plating plug for connection is more than or equal to 1 mu m, and meets the requirements of wear resistance, corrosion resistance, long service life, reliable connection and small contact resistance of the gold-plating plug.

Description

Processing technology of leadless plug electrogilding and plate surface gilding printed circuit board

Technical Field

The invention belongs to the technical field of printed circuit board processing, and particularly relates to a processing technology of a leadless plug electrogilding and surface gilding printed circuit board.

Background

With the development of electronic technology, various industrial control devices, military instruments and meters, aerospace products, medical instruments, communication terminal products and the like are developed towards high density, multiple functions and high reliability. Due to high density of the products, the used circuit design needs to use BGA, QFP and other high-end components, and a printed circuit board for mounting the high-density components needs to adopt a chemical nickel and gold plating process to meet the surface mounting requirement. Meanwhile, these high-density printed circuit boards must be designed with gold-plated plugs for communication with external circuits and systems. Because the service environments of the equipment are different, for example, the equipment is used on ships of navigation ships, various vehicles, various occasions of field operation and the like, the connection of the gold-plated plug is required to be reliable, the contact resistance is small, the gold-plated plug is wear-resistant, and the gold-plated plug can resist corrosion of various environments without generating connection faults. To meet this requirement, the gold-plated plug requires a gold-plating thickness of not less than 1 μm, and the plated layer is a gold-cobalt alloy layer, not a pure gold layer. The thickness of the gold plating layer for the surface mounting of the components is required to be more than or equal to 0.03 mu m, and the requirements can be met by using a chemical gold plating process. The same surface of a printed circuit board has two parts with different gold plating thickness requirements, the requirements can not be met simultaneously according to the prior art, and a new processing mode needs to be developed to meet the product requirements.

Disclosure of Invention

In order to overcome the defects, the invention provides a processing technology of a leadless plug electrogilding and surface gilding printed circuit board, which meets the requirements of two different gilding thicknesses on the same surface of one printed circuit board and different parts, thereby meeting the requirements of surface mounting and welding of electronic components such as BGA, QFP and the like and ensuring good weldability of the surface of a welding pad. But also can ensure that the thickness of the gold-plating layer at the position of the gold-plating plug for connection is more than or equal to 1 mu m, and meets the requirements of wear resistance, corrosion resistance, long service life, reliable connection and small contact resistance of the gold-plating plug.

The technical scheme adopted by the invention for solving the technical problem is as follows:

a processing technology of a leadless plug electrogilding and surface gilding printed circuit board at least comprises the following steps:

step 1, arranging a process lead when a circuit pattern of a circuit board is manufactured, and connecting a gold-plated plug serving as an external connecting channel together to form a same conductive network;

step 2, when the solder mask protection pattern is manufactured, all the welding pads needing to be welded, the welding pads mounted by the SMT, the gold-plated plugs and the process leads connected with the gold-plated plugs are exposed, and all the connection circuit patterns and the wire through holes are covered by the solder mask layer;

step 3, when a gold-plated plug pattern is manufactured, covering a layer of dry film layer for resisting electro-gold plating on the board surface of the circuit board, only exposing the plug part needing to be plated with gold and gold-plated clamping points on the process frame, completely covering the rest part of the circuit board, and plating a nickel and gold-cobalt alloy layer on the plug part in an electro-gold plating process;

step 4, setting exposed process wire patterns, covering all the circuit board surface with a corrosion-resistant dry film, only exposing the process wire pattern parts, etching the process wires connected with each gold-plated plug in a subsequent etching process, wherein no lead is left on each gold-plated plug, and separating different pins into different conductive networks;

step 5, printing a layer of chemical-resistant gold peelable glue layer on the gold-plated plug electroplated with the thick gold layer;

and 6, performing nickel immersion and gold processing on all the exposed patches and pads except the gold-plated plugs.

As a further improvement of the invention, in the step 3, in the gold electroplating process, the plug part is plated with nickel more than or equal to 2.54 μm, and the gold-cobalt alloy layer is more than or equal to 1.0 μm.

In a further improvement of the present invention, in the step 5, the thickness of the printed gold-resistant peelable glue layer is greater than 0.3 mm.

As a further improvement of the invention, in the step 6, nickel and gold deposition processing is carried out, so that nickel is more than or equal to 2.54 μm and gold is more than or equal to 0.03 μm in the coating of the patch and the bonding pad.

The invention has the beneficial effects that: the invention meets the requirements of two different gold plating thicknesses on different parts of the same surface of a printed circuit board, thereby not only meeting the requirements of surface mounting and welding of electronic components such as BGA, QFP and the like, but also ensuring the good weldability of the surface of the welding pad. But also can ensure that the thickness of the gold-plating layer at the position of the gold-plating plug for connection is more than or equal to 1 mu m, and meets the requirements of wear resistance, corrosion resistance, long service life, reliable connection and small contact resistance of the gold-plating plug.

Drawings

FIG. 1 is a schematic view of a printed circuit board according to the present invention;

FIG. 2 is a schematic diagram of a plate surface drilling pattern in step 10 according to the embodiment of the present invention;

FIG. 3 is a schematic diagram of the circuit pattern of the PCB according to step 15 of the embodiment of the present invention;

FIG. 4 is a schematic diagram of solder mask patterns of the PCB at step 17 according to the embodiment of the invention;

FIG. 5 is a schematic diagram of a gold-plated portion of a plug in step 18 according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a gold plating process line pattern to be removed in step 21 according to an embodiment of the present invention;

fig. 7 is a schematic view of a chemical resistant gold peelable glue pattern according to step 24 of the embodiment of the present invention.

Detailed Description

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

A processing technology of a leadless plug electrogilding and surface gilding printed circuit board comprises the following steps:

step 1, cutting an inner-layer core plate: according to the design size of the board surface, one or more double-sided copper clad laminate which meets the requirements of the product thickness and the copper foil and is convenient for process processing is cut.

Step 2, drying the plate: the double-sided copper clad laminate is dried to age the incompletely cured epoxy resin in the insulating substrate while relieving stress in the substrate.

Step 3, inner layer dry film: pasting photosensitive dry films on the front surface and the back surface of the inner layer plate, and manufacturing negative images of the 2 nd layer, the 3 rd layer and the n-1 th layer through processes of exposure, development and the like.

Step 4, etching the inner layer: and etching the copper layer on the surface of the board, which is not covered by the dry film, by using a special etching solution, and then performing a film removing process to manufacture an inner layer circuit pattern.

Step 5, inner layer AOI: and comparing the difference between the manufactured inner layer circuit pattern and the design pattern by an optical scanning method, and checking and correcting the circuit pattern.

Step 6, browning: and performing browning treatment on the inner layer circuit pattern, and increasing the binding force between the inner layer pattern and the prepreg during subsequent pressing.

Step 7, laminating: the inner core plate, the prepreg and the outer copper foil are stacked together according to the required sequence, and are pressed in a laminating machine, so that the inner core plate, the prepreg and the outer copper foil are combined together to form the integral multi-layer printed circuit board blank plate.

Step 8, targeting: and searching the inner layer target by using an X-RAY target drilling machine, and drilling a positioning target hole.

Step 9, routing the edges of the board: and (5) positioning by utilizing the positioning target holes, and milling waste materials around the plate by using a milling machine.

Step 10, drilling: holes of different diameters for mounting components and for connecting wires are drilled at designated positions according to design requirements, see fig. 2, on which via holes 1 are formed.

Step 11, chemical copper deposition: and depositing a conductive copper layer on the insulating base material in the hole of the printed circuit board by using a chemical processing process.

Step 12, electroplating the whole board: the electroless copper plating layer on the insulating base material is thickened by more than 5 mu m in an electroplating mode.

Step 13, transferring outer layer patterns: and pasting a photosensitive dry film on the board surface, and transferring the designed top layer circuit pattern and the bottom layer circuit pattern onto the board through the steps of exposure, development and the like to form an erect image pattern.

Step 14, pattern electroplating: and plating a positive image pattern part displayed on the printed circuit board with a copper layer of more than 25 μm and a tin coating of 5-8 μm by electroplating.

Step 15, alkaline etching: the dry film layer remained on the board surface by pattern transfer is removed, the copper layer covered by the dry film layer is exposed, the copper layer is etched by etching liquid, then the protective tin coating on the circuit is removed, a circuit pattern is manufactured, see fig. 3, a process frame 2 and a circuit pattern positioned in the process frame 2 are arranged on the printed circuit board, and a bonding pad 3, a plug-in hole 4, a wire passing hole 5, a BGA bonding pad 6, a gold-plated plug 7, a gold-plated process lead 8 for connecting the gold-plated plug, and a connecting circuit 9 are arranged on the circuit pattern.

Step 16, AOI inspection: and comparing the difference between the manufactured circuit pattern and the design pattern by an optical scanning method, and checking and correcting the circuit pattern.

Step 17, solder mask printing: printing a layer of solder resist meeting the color required by a customer on the printed circuit board with the circuit pattern manufactured, drying, exposing, developing and the like to ensure that the connecting circuit is covered by the solder resist, and the pad part, the gold-plated plug part and the lead-out process lead part of the gold-plated plug which need to be welded are all exposed to form the solder resist pattern, which is shown in figure 4.

Step 18, manufacturing a plug gold-plating pattern: the plate surface is covered with a special plating-resistant thick gold dry film layer, only the plug part needing gold plating and the gold plating clamping point 10 on the process frame are exposed, and the rest part of the plate is completely covered by the plating-resistant thick gold dry film layer, as shown in figure 5.

Step 19, plug gold electroplating: the printed circuit board with the exposed pattern of the gold-plated part of the plug is electroplated in a special production line for nickel and gold electroplating, the nickel plated part of the plug is more than or equal to 2.54 mu m, and the gold-cobalt alloy layer is more than or equal to 1.0 mu m, so that the gold-plated plug is wear-resistant and corrosion-resistant, does not expose copper when being plugged and unplugged for more than 500 times, and has long service life, reliable connection and small contact resistance.

Step 20, removing the special dry film for gold plating resistance: and removing a special electroplating-resistant thick gold dry film layer covered on the plate surface by using a special film removing liquid, and reducing and exposing SMT welding spots, gold-plated process wires and the like.

Step 21, exposing a process wire: and sticking a dry film special for corrosion resistance on the board surface, and exposing the process lead to be removed through the steps of exposure, development and the like. And the circuit patterns of the bonding pads, the gold-plated plugs and the like on the other parts are completely covered by the etching-resistant special dry film, as shown in fig. 6.

Step 22, etching a process wire: and placing the printed circuit board with the exposed process leads in an etching production line for processing, and etching the exposed process leads.

Step 23, removing the special dry film for etching resistance: and placing the printed circuit board subjected to the process lead etching into a film stripping production line, stripping the dry film special for corrosion resistance etching, and reducing circuit patterns such as covered bonding pads, gold-plated plugs and the like to ensure that the gold-plated plugs are not connected together and are respectively positioned in different electrical networks.

Step 24, printing a gold-resisting strippable glue layer: and printing a gold-plating resistant peelable glue layer 11 on the gold-plating plug part which is subjected to gold plating and meets the requirements of customers in a silk-screen printing mode, so as to protect the gold-plating plug from being damaged during gold plating. While the remaining patterns, such as patches, that need to be soldered are fully exposed, see fig. 7.

Step 25, electroless nickel and gold plating: the printed circuit board printed with the gold-resistant peelable glue layer is sent to a chemical nickel-gold plating production line for processing, nickel and gold deposition are carried out, the plating layers of the patch and the bonding pad are ensured, nickel is larger than or equal to 2.54 mu m, gold is larger than or equal to 0.03 mu m, and good weldability is achieved.

Step 26, removing the peelable glue layer: and removing the strippable adhesive layer on the surface of the printed circuit board after the chemical nickel plating and gold plating operation is finished, and reducing the gold plating plug pattern.

Step 27, printing characters: on the surface of the printed circuit board, a layer of character marks is printed to mark the installation position, indication and the like of each component.

Step 28, forming: the edge milling operation is carried out on the printed circuit board by using a milling machine, the processing technology frame is removed according to the design requirement, and the printed circuit board is divided into a block unit, as shown in figure 1.

Step 29, cleaning: scrubbing with a soft brush and ultrasonic cleaning to remove surface pollution and dust, and drying.

Step 30, electrical testing: and carrying out open circuit and short circuit tests and insulation tests on the circuit patterns of the multilayer leadless plug electrogilding and surface gold-plated printed circuit board.

Step 31, final check: and checking the integrity of the graph of the board surface and the conformity of the structure size and the design file.

Step 32, packaging: and (5) inspecting the qualified finished product, packaging according to the requirements of the client, and shipping the finished product for use by the client.

Tests prove that the leadless plug electrogilding and plate-surface-gilding printed circuit board manufactured by the processing method has the advantages of good wear resistance and corrosion resistance, reliable connection and long service life.

Therefore, the invention meets the requirements of two different gold plating thicknesses on the same surface of a printed circuit board and different parts, not only meets the requirements of surface mounting and welding of electronic components such as BGA, QFP and the like, but also ensures that the surface of the welding pad has good weldability. But also can ensure that the thickness of the gold-plating layer at the position of the gold-plating plug for connection is more than or equal to 1 mu m, and meets the requirements of wear resistance, corrosion resistance, long service life, reliable connection and small contact resistance of the gold-plating plug.

In the previous description, numerous specific details were set forth in order to provide a thorough understanding of the present invention. The foregoing description is only a preferred embodiment of the invention, which can be embodied in many different forms than described herein, and therefore the invention is not limited to the specific embodiments disclosed above. And that those skilled in the art may, using the methods and techniques disclosed above, make numerous possible variations and modifications to the disclosed embodiments, or modify equivalents thereof, without departing from the scope of the claimed embodiments. Any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A processing technology of leadless plug electrogilding and plate surface gilding printed circuit board is characterized by at least comprising the following steps:

2. The leadless plug electrogilding and plat-platting printed circuit board processing technology as claimed in claim 1, characterized in that: in the step 3, in the gold electroplating process, the plug part is plated with nickel more than or equal to 2.54 microns, and the gold-cobalt alloy layer is more than or equal to 1.0 micron.

3. The leadless plug electrogilding and plat-platting printed circuit board processing technology as claimed in claim 1, characterized in that: in the step 5, the thickness of the printed gold-resisting strippable glue layer is more than 0.3 mm.

4. The leadless plug electrogilding and plat-platting printed circuit board processing technology as claimed in claim 1, characterized in that: and 6, performing nickel deposition and gold processing to ensure that nickel is more than or equal to 2.54 mu m and gold is more than or equal to 0.03 mu m in the coating of the patch and the bonding pad.