How to solve the problem of PCB board plating clip film?


With the rapid development of PCB industry, PCB is gradually moving towards the direction of high precision fine line, small aperture, high aspect ratio (6:1-10:1). The hole copper requirement is 20-25um, and DF line distance ≤4mil board. Generally, PCB companies have the problem of electroplating film clamping. Film clip will cause a direct short circuit, affecting the ONE-TIME yield of PCB board through AOI inspection, serious film clip or points can not be repaired directly resulting in scrap.


Graphic illustration of graphic electroplating clip film problem:

How to solve the problem of PCB board plating clip film

Analysis of the principle of PCB board clamping film

(1) If the copper thickness of graphic electroplating line is greater than the thickness of dry film, it will cause film clamping. (The dry film thickness of general PCB factory is 1.4mil)

(2) If the thickness of copper and tin on graphic electroplating line exceeds the thickness of dry film, film clip may be caused.

PCB board clamping film analysis

1. Easy to clip film board pictures and photos

How to solve the problem of PCB board plating clip film?

In FIG. 3 and FIG. 4, it can be seen from the pictures of the physical plate that the circuit is relatively dense, and there is a large difference between the ratio of length and width in the engineering design and layout, and the adverse current distribution. The minimum line gap of D/F is 2.8mil (0.070mm), the smallest hole is 0.25mm, the plate thickness is 2.0mm, the aspect ratio is 8:1, and the hole copper is required to be more than 20Um. It belongs to the process difficulty board.

2. Analysis of reasons for film clamping

The current density of graphic electroplating is large and the copper plating is too thick. There is no edge strip at both ends of the fly bar, and thick film is plated in the high current area. The fault current of ox is larger than that of actual production plate. The C/S plane and S/S plane are connected inversely.

Plate clips with too small 2.5-3.5mil spacing.

The current distribution is not uniform, copper plating cylinder for a long time without cleaning the anode. Wrong current (wrong type or wrong plate area) The protection current time of PCB board in copper cylinder is too long.

 The layout design of the project is not reasonable, the effective electroplating area of the project graphics is wrong, etc. PCB board line gap is too small, difficult board line graphics special easy clip film.

Effective improvement scheme for clip film

1. reduce the graph current density, appropriate extension of copper plating time.

2. Increase the plating copper thickness of the plate appropriately, reduce the plating copper density of the graph appropriately, and relatively reduce the plating copper thickness of the graph.

3. The copper thickness of the platen bottom is changed from 0.5OZ to 1/3oz copper platen bottom. The plating copper thickness of the plate is increased by about 10Um to reduce the current density of the graph and the plating copper thickness of the graph.

4. For the board spacing < 4mil procurement 1.8-2.0mil dry film trial production.

5. Other schemes such as modification of typesetting design, modification of compensation, line clearance, cutting ring and PAD can also relatively reduce the production of film clip.

6. Electroplating production control method of film plate with small gap and easy clip

1. FA: First try the edge clamping strips at both ends of a flobar board. After the copper thickness, line width/line distance and impedance are qualified, finish etching the flobar board and pass AOI inspection.

2. Fading film: for the plate with D/F linegap < 4mil, the etching speed of fading film should be adjusted slowly.

3. Skills of FA personnel: pay attention to current density assessment when indicating the output current of the plate with easy clip film. Generally, the minimum line gap of the plate is less than 3.5mil (0.088mm), and the current density of electroplated copper is controlled within ≦12ASF, which is not easy to produce clip film. In addition to the line graphics particularly difficult board as shown below:

How to solve the problem of PCB board plating clip film

The minimum D/F gap of this graphic board is 2.5mil (0.063mm). Under the condition of good uniformity of gantry electroplating line, it is recommended to use ≦10ASF current density test FA.

How to solve the problem of PCB board plating clip film?

The minimum line gap of the graphic board D/F is 2.5mil (0.063mm), with more independent lines and uneven distribution, it can not avoid the fate of film clip under the condition of good uniformity of electroplating line of general manufacturers. The current density of graphic electroplating copper is 14.5ASF*65 minutes to produce film clip, it is recommended that the graph electric current density is ≦11ASF test FA.

Personal experience and summary

I have been engaged in PCB process experience for many years, basically every PCB factory making board with small line gap more or less will have film clamping problem, the difference is that each factory has different proportion of bad film clamping problem, some companies have few film clamping problem, some companies have more film clamping problem. The following factors are analyzed:

1. each company’s PCB board structure type is different, PCB production process difficulty is different.

2. Each company has different management modes and methods.

3. from the perspective of the study of my many years of accumulated experience, to a small plate must pay attention to the first line gap can only use a small current density and appropriate to extend the time of copper plating, the current instructions according to the experience of current density and the copper plating is used to assess a good time, pay attention to plate method and operation method, aimed at the minimum line from 4 mil plate or less, try a fly the FA board must have the AOI inspection without the capsule, At the same time, it also plays a role in quality control and prevention, so that the probability of producing film clip in mass production will be very small.

In my opinion, good PCB quality requires not only experience and skills, but also good methods. It also depends on the execution of the people in the production department.

Graphic electroplating is different from the whole plate electroplating, the main difference lies in the line graphics of various types of plate electroplating, some board line graphics themselves are not evenly distributed, in addition to the fine line width and distance, there are sparse, a few isolated lines, independent holes all kinds of special line graphics. Therefore, THE author is more inclined to use FA (current indicator) skills to solve or prevent the problem of thick film. The improvement action range is small, quick and effective, and the prevention effect is obvious.