1. Production requirements
The requirements for sheet material, sheet thickness, copper thickness, process, solder mask/character color, etc. are clear. The above requirements are the basis for making a board, so R&D engineers must write clearly. According to the customers I have contacted, Gree has done a relatively good job. The technical requirements of each document are clearly written, even if it is usually us I think that the most normal use of green solder resist ink and white characters are written in the technical requirements, and some customers can avoid it if they can. If they don’t write anything, they will send it to the manufacturer for proofing production, especially some manufacturers have some special requirements. It was not written out, causing the manufacturer to consult the requirements in this regard first after receiving the email, or some manufacturers did not meet the requirements in the end.
2. Drilling design
The most direct and biggest problem is the design of the minimum aperture. Generally, the minimum aperture in the board is the aperture of the via hole. This is directly reflected in the cost. The via hole of some boards can obviously be designed as a 0.50MM hole, that is, Only put 0.30MM, so the cost will directly rise sharply, and the manufacturer will increase the quotation if the cost is high. In addition, there are too many vias. Some DVDs and digital photo frames are filled with vias on the entire board. 1000 holes. I have done too many boards in this area. I think it should be 500-600 holes. Of course, some people will say that more holes are good for the signal conduction and heat dissipation of the board. I think this is a balance. , while controlling these aspects, it will not lead to an increase in costs.
I can give an example here: Our company has a client who is a DVD manufacturer in Shenzhen, and the volume is very large. It was the same situation at the beginning of the cooperation. Later, the cost was really a big problem for both parties. After cooperation with R&D Communication, increase the diameter of the via hole as much as possible, delete some via holes on the large copper skin, replace the heat dissipation hole in the middle of the main IC with four 3.00MM holes, so that the cost of drilling is reduced. The drilling fee can be reduced by tens of dollars per square meter, which is a win-win situation for both parties; in addition, some slots, such as 1.00MM X 1.20MM ultra-short slots, are really very important for manufacturers. Difficult to make, firstly it is difficult to control the tolerance, secondly, the slots that drilled are not straight, some are curved, we have made some boards like this before, but the boards with a few cents of RMB, because the slot holes are unqualified, buckle 1 USD/piece, we also communicated with customers about this issue, and then directly switched to 1.20MM round holes.
3. Line design
For line width and line spacing, and open circuit and short circuit, etc., are the most common ones for manufacturers. Apart from special ones, for some more conventional boards, I think the larger the line width and line spacing, the better. I have seen some documents. There are several bends in the middle of the straight line. There are several lines in the same row with the same width and different spacing. For example, the spacing in some places is only 0.10MM, and in some places it is 0.20MM. When wiring, you must pay attention to these details; there are also some line pads or traces that are only 0.127MM away from the large copper skin, which increases the difficulty for manufacturers to handle the film. It is best to have a distance between the pad trace and the large copper skin Above 0.25MM.
Some traces have a very small safe distance from the periphery or V-CUT, so it’s okay if the manufacturer can move them, while others must be designed by R&D. It is the same network, but it is not connected. In the end, the manufacturer communicated with R&D and found that it was a short circuit, and then re-edited the data. This situation is not uncommon. Experienced engineers may be able to see that the inexperienced If you just follow the design file, the result is that you either modify the file and re-proof it or scrape it with a blade or fly the lead. For the board with impedance requirements, some R&D does not write, and finally it does not meet the requirements. In addition, the via holes of some boards are designed on the SMD PAD, and the tin will leak down during soldering.
4. Design of solder mask
The problem that is more likely to occur in terms of solder resistance is that some copper skins or traces need to expose copper. For example, solder resist windows should be added on the copper skin to facilitate heat dissipation, or copper should be exposed on some high-current traces. Generally, these additional solder resists are placed on the Soldermask layer, but some R&D will create another layer. , placed on the mechanical layer, placed on the forbidden wiring layer, all kinds, everything, not to mention, not to specify, it is difficult for people to understand. I think it is best to put it on the TOP Soldermask or BOTTOMSoldermasK layer, which is the easiest to understand. In addition, it is necessary to explain whether the green oil bridge in the middle of the IC should be retained, and it is best to give an explanation.
5. Character design
The most important thing about characters is the design requirements of character width and character height. Some boards are not very good in this aspect. The same component even has several character sizes. As a manufacturer, I think it is not beautiful. I think we must learn from those motherboard manufacturers. , row after row of component characters, the same size, makes people look pleasing to the eye. In fact, it is best to design the characters to be above 0.80*0.15MM, and the silk screen printing process of the manufacturer is also better for printing; in addition, some large white oil blocks, such as those on the crystal oscillator, or some row plugs, some manufacturers need to use white oil to cover Some of them have to expose the pads, and these must be explained; I have also encountered some wrong positions of the silk screen, such as the characters of resistors and capacitors are swapped, but these errors are still rare; there is also a need to Added marks, such as UL mark, ROHS words, PB mark, manufacturer's LOGO and serial number.
6. Shape design
Today's boards are rarely rectangular and irregular, but there are mainly several line drawing frames, which make people unable to choose. In addition, in order to improve the utilization rate of equipment (such as SMT), They all have to make V-CUT impositions, but the resulting boards have different spacing, some have spacing and some have no spacing. It is okay to make samples for the first factory, but it will be more troublesome if you need to change suppliers later. If the second factory If you don't fight according to the first factory, the steel mesh will not fit. Therefore, in the absence of special circumstances, it is best not to join together with spacing; in addition, some file designs may draw a small rectangular hole for the slot to be drilled and place it on the shape layer. This situation is more common in files designed by PROTEL software. Relatively speaking, PADS is better. If it is placed on the shape layer, it is easy for the manufacturer to misunderstand that the hole should be punched out or made into an NPTH attribute. For some that require the PTH attribute, it is easy to cause problems.
There is no need to talk about other blue glue process or carbon oil process boards here.
English
Chinese