CN114126251A

CN114126251A - High-precision fine solder-resisting bridge method

Info

Publication number: CN114126251A
Application number: CN202111488326.XA
Authority: CN
Inventors: 刘鹍; 李晓雷; 熊俊杰; 刘期刚; 郎广志
Original assignee: Guangde Jinteng Electronic Technology Co ltd
Current assignee: Guangde Jinteng Electronic Technology Co ltd
Priority date: 2021-12-08
Filing date: 2021-12-08
Publication date: 2022-03-01

Abstract

The invention belongs to the technical field of solder bridges, and particularly relates to a high-precision fine solder bridge welding method. According to the invention, the traditional one-time solder mask manufacturing process is changed, and a two-time solder mask manufacturing process is adopted, wherein the first solder mask manufacturing process aims to fill and level the base material between the lines, so that the red condition of the lines can not occur when the thickness of the ink is reduced for the second time. On the premise of meeting the resistance welding quality, the thickness of the secondary resistance welding ink is reduced, the lateral erosion during resistance welding development is reduced, a stable and reliable resistance welding bridge with high compactness is obtained, a reliable and stable resistance welding layer is obtained, and the phenomenon of tin connection short circuit in the welding process is avoided.

Description

High-precision fine solder-resisting bridge method

Technical Field

The invention belongs to the technical field of processing of rigid-flex boards, and particularly relates to a high-precision fine solder bridge resistance method.

Background

The solder resist is used as a protective layer of the circuit, so that the copper of the circuit can be effectively protected from being corroded, and the short circuit of the circuit caused by foreign matters or electrolytic solution after the circuit is pasted can be avoided, so that the solder resist is widely applied to the field of circuit board manufacturing.

The existing solder mask bridge manufacturing method is a one-time direct manufacturing method, after solder mask ink is used for pre-fixing a telephone, the telephone is subjected to light fixing, and then development is carried out, so that a required solder mask bridge is manufactured, and the solder mask bridge is ensured to be free from short circuit among pads during welding.

With the increasing precision of electronic devices, the requirements on the PCB are also increasing, and the PCB lines are also becoming finer. Meanwhile, with the development of packaging technology, the packaging area is reduced, the functions are more powerful, the number of IC pins is more and more, and the IC spacing is smaller and smaller. Even solder bridges between some of the IC pads are designed to be less than 3 mils, which exceeds the solder mask manufacturing capability of most PCB manufacturing factories.

Research and analysis on the solder mask bridge manufacturing capability of a company show that the main influence factors of the solder mask bridge manufacturing are the influence of the solder mask thickness and the solder mask contraposition precision of a circuit board, and the thickness of the solder mask is closely related to the finished product copper thickness of the circuit board. The thicker the copper is, the thicker the solder resist thickness is in order to ensure that no false copper is exposed on the circuit board (the solder resist ink at the wire shoulder is thin, which causes insulation reduction); the thicker the solder resist thickness is, the larger the development amount of development is, and the larger the amount of side wall undercut during development is, resulting in a situation where the bottom of a fine solder resist bridge is floated to form a bridge drop.

Disclosure of Invention

The invention aims to: in order to solve the technical problem, a high-precision fine solder bridge method is provided.

The technical scheme adopted by the invention is as follows:

a high-precision fine solder bridge welding method comprises the following steps:

firstly, cleaning a corresponding PCB product before assembly welding;

step two, performing assembly welding and hole plugging on corresponding via holes according to requirements, and performing two-side solder mask silk-screen printing, standing, pre-baking, exposure, development and development inspection;

thirdly, post-curing the PCB after development inspection, and completely curing the printing ink;

fourthly, mechanically polishing the cured PCB product to expose the outer copper layer;

step five, cleaning the mechanically polished plate;

and sixthly, performing two-side assembly welding silk-screen printing, standing, pre-baking, exposing and developing on the cleaned PCB product.

Preferably, in the first step, the cleaning before solder mask adopts treatment methods including but not limited to sand blasting, volcanic ash, medium roughening, super roughening, and the like to remove oxidation, foreign matters, and the like on the surface of the PCB board, and roughen the copper surface.

Preferably, in the second step, the required via hole is plugged; the solder mask silk-screen printing adopts whole-board silk-screen printing or dot-screen printing, and the solder mask thickness is made to be larger than the copper thickness; the exposure process adopts selective exposure, the device hole, the via hole required to be windowed, the position of the windowed substrate and all copper surfaces are not exposed, and the rest positions are exposed.

Preferably, in the third step, the post-curing completely cures the ink according to the conventional curing parameters.

Preferably, in the fourth step, the mechanical polishing process uses but is not limited to a mechanical processing mode such as a ceramic polishing plate, a sand belt polishing plate, a non-woven fabric polishing plate, and the like, and the plate surface needs to be polished after the plate is polished.

Preferably, in the first step and the fifth step, the surface of the PCB is cleaned by using a treatment method including but not limited to sand blasting, volcanic ash, medium roughening, super roughening and the like to remove oxidation, foreign matters and the like of the surface of the PCB.

Preferably, in the second step and the sixth step, the adopted silk-screen process comprises whole-plate silk-screen printing and stop-point silk-screen printing.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

the invention changes the traditional one-time solder mask manufacturing process, adopts a two-time solder mask manufacturing process, and the first solder mask manufacturing process aims to fill and level the base material between the circuits, thereby ensuring that the circuits do not turn red when the thickness of the ink is reduced for the second time. On the premise of meeting the resistance welding quality, the thickness of the second-time resistance welding ink is reduced, the side erosion amount during resistance welding development is reduced, a stable and reliable resistance welding bridge with high compactness is obtained, a whole reliable resistance welding layer is further obtained, the tin-connecting short circuit is guaranteed not to occur in the welding process, the problem of bridge falling of an IC resistance welding bridge of a circuit board is solved through certain processing procedure adjustment and corresponding technical parameters, and particularly the reliability of a small group welding bridge smaller than or equal to 3mil is improved.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below by way of examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships only for the convenience of describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention; the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; furthermore, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, as they may be fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The embodiment provides a high-precision fine solder resist bridge method, which comprises the following steps:

the first step is as follows: and (3) horizontally blasting the PCB (printed circuit board) with a sand blasting (volcanic ash and chemical cleaning) line to remove the oxidation and impurities on the PCB.

The second step is that: fixing the PCB, plugging holes (if necessary) by using a screen (an aluminum sheet net and an exposure stop point net), directly performing screen printing of the two-side oil after plugging the holes, and directly performing screen printing of the two-side oil on the board without plugging the holes.

The third step: standing the PCB after silk-screen printing for more than 1H (the specific time can be determined according to the thickness of copper), and then pre-baking.

The fourth step: developing the ink at the positions of the device holes, the windowing through holes and the windowing base material by using a negative film or direct laser imaging exposure, and reserving the solder resist ink at the rest positions

The fifth step: and curing the solder resist ink of the board after development inspection, wherein parameters can be determined according to the characteristics of the ink, the thickness of the ink and whether to plug holes.

And a sixth step: and mechanically polishing the cured PCB to expose the outer layer circuit copper, and inspecting by using AOI scanning after polishing.

The seventh step: repeating the first step, the second step and the third step, but controlling the thickness of the solder mask silk screen printing to be 8-10 μm

Eighth step: and exposing by using a normal negative film or data to expose all positions of device holes, bonding pads and the like.

The ninth step: and (5) normal post-manufacturing procedures.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A high-precision fine solder bridge welding method is characterized by comprising the following steps: the method comprises the following steps:

firstly, cleaning a corresponding PCB product before assembly welding;

step five, cleaning the mechanically polished plate;

2. The high-precision fine solder mask bridge method of claim 1, wherein: in the first step, the cleaning before the solder mask adopts treatment methods including but not limited to sand blasting, volcanic ash, medium roughening, super roughening and the like to remove oxidation, foreign matters and the like on the surface of the PCB and roughen the copper surface.

3. The high-precision fine solder mask bridge method of claim 1, wherein: in the second step, hole plugging treatment is carried out on the required through hole; the solder mask silk-screen printing adopts whole-board silk-screen printing or dot-screen printing, and the solder mask thickness is made to be larger than the copper thickness; the exposure process adopts selective exposure, the device hole, the via hole required to be windowed, the position of the windowed substrate and all copper surfaces are not exposed, and the rest positions are exposed.

4. The high-precision fine solder mask bridge method of claim 1, wherein: and in the third step, the post-curing completely cures the printing ink according to the conventional curing parameters.

5. The high-precision fine solder mask bridge method of claim 1, wherein: in the fourth step, the mechanical polishing process uses but is not limited to mechanical processing modes such as ceramic grinding plates, abrasive belt grinding plates, non-woven fabric grinding plates and the like, and the plate surface needs to be polished after the plate is ground.

6. The high-precision fine solder mask bridge method of claim 1, wherein: in the first step and the fifth step, the cleaning board surface adopts treatment methods including but not limited to sand blasting, volcanic ash, medium coarsening, super coarsening and the like to remove oxidation, foreign matters and the like of the PCB board surface.

7. The high-precision fine solder mask bridge method of claim 1, wherein: in the second step and the sixth step, the adopted silk-screen process comprises whole-plate silk-screen printing and stop point silk-screen printing.