Analysis of plate deformation in PCB process

- Sep 22, 2018-

1. Causes and solutions of film deformation:

The reason:

(1) temperature and humidity control failure

(2) the temperature rise of the exposure machine is too high


(1) usually the temperature control in 22 + 2 ℃, humidity in 55% + / - 5% RH.

(2) use a cold light source or an aerator with cooling device and constantly replace the backup film

Ii. Process method of film deformation correction:

1, in the mastery of digital programming instrument operation technology, the first film and drilling test board, two deformation measure its length, width, on the digital programming device according to the deformation on a long or shortening, the size of the hole, it with long or shorten the hole after drilling test plate to be close the deformation of the film, splicing of film from all the work, to ensure the integrity of the graphics and accuracy.This method is called "change hole location method".

2. According to the physical phenomenon that the negative changes with the change of environment temperature and humidity, the negative in the sealing bag is taken out before copying the negative. Under the working environment, the negative is hung for 4-8 hours to make it deform before copying.

3. For the graphs with simple lines, large line width and spacing and irregular deformation, the deformation part of the plate can be cut and compared to the hole position of the drilling test plate, which can be re-inserted before being copied. This method is called "splicing".

4. The hole on the test plate is used to enlarge the line sheet of the welding plate to deform and deform, so as to ensure the minimum ring width technical requirements. This method is called "welding plate overlapping method".

5. After enlarging the images on the deformed film in proportion, re-texturing is made. This method is called "mapping method".

6. Use a camera to enlarge or reduce the distorted figure, and call this method "photographic method".

Notes to relevant methods:

1. Splicing method:

Application: the line is not too dense, each layer of film deformation inconsistent film;It is especially suitable for the deformation of resistance welding film and multilayer power supply layer film.

Not applicable: film with high density, wire width and spacing less than 0.2mm;

Note: during splicing, wire should be cut as little as possible, and welding pad should not be damaged.When rework after splicing copy, attention should be paid to the correctness of the connection relationship.

2. Hole location changing method:

Application: the deformation of each layer of film is consistent.The same applies to line - intensive film;

Not applicable: film deformation is not uniform, local deformation is particularly serious.

Note: after the hole position is lengthened or shortened by using the programming device, the hole position of out-of-tolerance should be reset.

3. Hanging method:

Apply;A negative that has not yet deformed and prevents deforming after copying;

Not applicable: distorted film.

Cautions: hang the film in a ventilated and dark environment (safe or not) to avoid contamination.Make sure that the drying place is consistent with the temperature and humidity of the work place.

4. Overlapping pads:

Application: the graph line is not too dense, the line width and the spacing are larger than 0.30mm;

Not applicable: in particular, users have strict requirements on the appearance of printed circuit boards;

Note: due to overlapping copies, the pad is oval.After overlapping and copying, line, disk edge halo and deformation.

5. Photography:

Suitable for: the film has the same deformation proportion in the direction of length and width.

Not applicable: film length and width are out of shape.

Note: the focus should be accurate when photographing to prevent line deformation.The negative has a lot of wastage. In general, it is necessary to have a lot of debugging before obtaining satisfactory circuit graphics.