The hottest printed circuit board printing materia

Printed circuit board printing materials and operation technology (I)

Abstract This paper briefly describes the technical specifications, process parameters and production operation technology of various kinds of printing materials used in the production of printed circuit boards: anti etching printing materials, anti electroplating printing materials, anti welding printing materials, characters, marking printing materials, plug hole printing materials, conductive printing materials, strippable printing materials, solder paste printing materials and so on

key words: printed circuit board silk printing material printed circuit board production is inseparable from silk printing and printing material. Printing material, also known as ink, is widely used in the manufacturing process of printed circuit. Nowadays, electronic products are developing in the direction of high precision, high density, high reliability and micro technology, which puts forward higher requirements for silk printing included in printed circuit manufacturing technology. With the rapid development and progress of printing materials in recent years, many new printing materials have been developed and continuously improved to meet the production process requirements of fine decorated printed circuit boards

at present, the printed board manufacturing industry has formed a series of special printing materials, which are roughly classified as follows:

(1) anti etching printing materials

(2) anti electroplating printing material

(3) solder resist

(4) character and mark printing materials

(5) plug hole printing material

(6) conductive printing material

(7) strippable printing material

(8) solder paste

I. anti etching printing material

anti etching printing material is one of the most common printing materials developed and used in the production of printed boards, and is used in the subtraction process. Its function is to print on the copper foil to protect the circuit pattern from being etched by the etching solution. At present, many brands have been formed, but they can be divided into two categories: (1) self drying type or thermosetting type; (2) Light solid type

(1) self drying or thermosetting

self drying or thermosetting anti-corrosion printing material is a liquid printing material composed of synthetic resin, filler, pigment and additives, which first adjust the brightness of the bulb to the darkest place and solvent

self drying printing materials are dried at room temperature for one hour or less to form films; Thermosetting printing materials are required to be dried in a hot air circulating oven at 80 ~ 100 ℃ for 8 ~ 10 minutes, and the film hardness after drying can reach 2H. Some varieties are only resistant to acid etching solution, while others are both resistant to acid and alkaline etching solution. The film is usually removed with 1% - 3% NaOH solution. The storage life of the printing material is one year, and the pigment is mostly blue or black

(2) photosolid

photosolid resist is generally composed of photosensitive resin, photosensitive monomer, photosensitive agent, filler, auxiliary and pigment. Its main feature is that it will not dry or block on the plate during silk printing, but under the irradiation of ultraviolet light (UV light), it will produce light cross-linking polymerization reaction in just a few seconds, which can cure quickly. The hardness of the film is also 2h, and it is also resistant to acid and alkaline etching solutions; At the same time, because it does not contain solvents, it will not pollute the environment and is suitable for the automatic assembly line production of single-sided printed boards. The storage period of printing materials is about 4 ~ 6 months

the usual curing condition of printing material is: high pressure mercury lamp 80 w/cm × 3. The irradiation distance is 10 cm, the conveying speed of the light curing machine is 4 ~ 6 m/min, the film is removed with 3 ~ 5% NaOH solution, and the temperature is 30 ~ 50 ℃

the resolution of thermosetting and photosetting printing materials is about 200 μ M, and make graphics with line width and spacing of more than 0.25 mm

II. Anti electroplating printing material

anti electroplating printing material, like anti etching printing material, is also a liquid type printing material dissolved in dilute alkali. It is mainly used for the production of outer circuit graphics of double-sided or multi-layer printed boards. Its function is to print negative circuit graphics, which prevents metal ions from forming electroplated coatings on the graphics during electroplating. Anti electroplating printing materials can also be used as anti etching printing materials

anti electroplating printing materials are mainly divided into thermosetting type and liquid photosensitive type

(1) thermosetting

thermosetting printing materials are composed of synthetic resins, fillers, additives, pigments and solvents. The drying temperature of the film is 80 ~ 100 ℃, and the time is 8 ~ 10 min. the pencil hardness of the dried film is about 2H. It can withstand copper plating, tin lead alloy, nickel, gold plating solution and acid or alkaline etching solution. It is suitable for the production of printed boards with line width and spacing of more than 0.25 mm

the printing of anti electroplating printing materials requires that the film thickness after drying meet certain requirements. If the film thickness is too thin, the line pattern will extend to both sides during pattern electroplating, resulting in electroplating overflow, that is, the so-called "mushroom" phenomenon. In serious cases, it will also cause a short circuit, which will make it difficult or unclean to remove ink when removing the printing materials, and the residual film during etching will cause sawtooth or unclean etching of graphic wires

the use of photosetting printing materials is not very popular. Although photosetting printing materials have the advantages of good printing performance and thick coating, it is difficult to master the degree of curing and inconvenient deinking, which affect its promotion and use

the average level of printing technology is that the line width and spacing are about 0.2 mm. It is difficult to break through this level by using thermosetting printing material operation process

deinking adopts 3% - 5% NaOH solution, and the storage life of printing materials is one year

(2) liquid photosensitive

liquid photosensitive anti electroplating printing material is a kind of printing material developed to solve the production of fine wire graphics, commonly known as wet film. It overcomes some problems in the production process of thermosetting anti electroplating printing material and dry film, and is suitable for the production of thin wires and ultra-fine wires. The width of the thinnest line can be up to three wires (0.125 mm) or four wires (0.075 mm) between two pads with a center of 2.54 mm. It can also be used for high-precision handicrafts, STM hollowed out templates, and pad printing intaglio production

liquid photosensitive anti electroplating printing material can also be used for the production of fine wires in the inner layer of multi-layer boards, as an anti etching printing material

it is composed of photosensitive resin, photosensitive agent, filler, auxiliary, pigment and solvent. The resolution of the printing material is 50 ~ 100 μ m. It has good adhesion with copper-clad foil, and there are no defects such as wire burr, notch, short circuit and so on caused by edge infiltration caused by interfacial bubbles in dry film production

printing materials are usually operated within the safe yellow light area, and the storage period is about one year

the brief process flow of liquid photosensitive anti electroplating printing material is as follows:

coating  pre drying  cooling  exposure  imaging  curing  electroplating  removing printing material  etching

11. Lifting cylinder dispensing height: 0 (5) 00mma Coating

150 ~ 300 mesh silk, manual full-scale printing, printing a and B sides. When used in the electroplating process of double-sided board graphics, choose low mesh silk, and when used in the etching process of the inner layer of multi-layer board, choose high mesh silk

b. pre drying

hot air circulation oven 80 ~ 100 ℃, 8 ~ 10 minutes, both sides of a and B are baked at the same time

take it out after baking and cool it to room temperature

c. exposure

when exposed after cooling, the UV wavelength is 300 ~ 400 nm, and the exposure energy is controlled at 100 ~ 300 m. when the hydraulic pump continues to work and the worktable fundamentally stops rising, the regulator equalizes thallium j/cm2, and the Stuart 21 densitometer is 7 ~ 8

d. imaging

1% Na2CO3 solution, imaging solution temperature 28 ~ 32 ℃, spray pressure 0.2 ~ 0.3 mp/cm2, time 30 ~ 60 s (seconds)

e. electroplating

electroless copper, tin lead alloy, nickel, gold solvent

f. deinking

3% ~ 6% NaOH solution, swelling, swelling and stripping of the film at 50 ~ 60 ℃

g. etching

acid resistance or alkaline etching solution, but the temperature of the etching solution is required not to be too high