The first is exposure

Exposure is that when the PCB manufacturer is processed, under ultraviolet light, the light -induced agent absorbs the optical can be decomposed into free base, and the free base will cause the optical aggregate single to converge the cross -linking response. Body -shaped macromolecular structure. The exposure is generally performed in the automatic double -sided exposure machine. Now the exposure machine can be separated by the cooling source, which can be separated and water -cooled.

Factors affecting exposure imaging quality

Factors affecting the quality of exposure imaging, in addition to the performance of the optical resistance of the dry membrane, the control of the selection of light sources, the control of the exposure time (exposure), and the quality of the photographic version are important factors that affect the quality of exposure imaging.

1) Selection of light sources

Any kind of dry film has its own unique spectral absorption curve, and any kind of light source also has its own emission spectrum curve. If the spectrum of a dry membrane absorbs the main peak can overlap the main peak with the spectrum of a certain light source or most of the overlap, the two are well matched and the exposure effect.

The spectrum absorption curve of domestic dry membranes shows that the spectral absorption area is 310-440Nm (millilitermate). From the distribution of the spectral energy of several light sources, it can be seen that the wavelength of pickups, high -pressure mercury lamps, and iodine lamps has a large relative radiation strength in the wavelength range of 310-440nm, which is an ideal light source for dry membrane exposure. The lamp is not suitable for the exposure of the dry membrane.

After the type of light source is selected, the large power of light source should be considered. Because the light intensity, high resolution, short exposure time, the degree of heating deformation of the photographic version is also small. In addition, the design of the lamps is also very important. It is necessary to try to make the inlet light uniformity and high parallelism to avoid or reduce the effect after exposure.

2) Control of exposure time (exposure volume)

During the exposure process, the optical polymerization reaction of the dry membrane is not "attractive" or "one exposure is completed", but through three stages.

Due to the obstacles of oxygen or other harmful impurities in the dry membrane, it is necessary to pass through a induced process. During the process, the degradation of the luminous group was consumed by oxygen and impurities. However, when the induction period is over, the optical polymerization reaction of the monomer is quickly carried out, and the viscosity of the glue membrane increases rapidly, which is close to the degree of mutation. This is the stage of rapid consumption of light -sensitive monomers. At this stage, the time occupied during the exposure process The ratio is very small. When most of the optical monomer is consumed, it enters the depletion of the monomer. At this time, the optical aggregation reaction has been completed.

Correctly controlling the exposure time is a very important factor in obtaining excellent dry membrane resistance images. When the exposure is insufficient, due to the insufficient polymerization of the monomer, in the process of seeking, the glue membrane is softened, the lines are unclear, the color is dull, and even off -gum. And even fall off. When exposed too much, it will cause difficulties such as showing development, brittle glue film, and leftover. What's more serious is that the incorrect exposure will generate the width of the image lines. Excessive exposure will make the lines of the graphic electroplating thinner, making the lines of etching thicker. On the contrary Tripped the lines of etching.