Premise summary: when designing SMT steel mesh, some customers will think that the opening size of the steel mesh is all the same as the design drawing of the source document. In fact, this understanding is wrong. For the opening, we are more concerned with the tin lowering effect of the hole location, so we will make appropriate modifications to some components, (for example, the SD card seat button. It is a position that requires a large amount of tin, so the hole position at this position will be increased to open when designing the steel mesh. Although the tin amount will be brushed on the green oil, it will shrink and flow back to the welding pad after passing the furnace, showing a full state, which will not lead to false welding. Another example is

Some components (QFN, BGA type) are easy to cause tin connection or tin stacking when opening holes according to 1:1, and the opening will be reduced).

1、 The document has a steel mesh layer, commonly known as the paste layer, so jialichuang is made according to the paste layer, with the following exceptions:

1) Obvious standard gold finger 2) obvious pot name patch button 3) obvious RF antenna above three points does not open, and all others are made according to paste (steel mesh layer). (defined by jialichuang): paste layer, which is generally designed for files in the format of “PCB suffix”, such as (top paste, bottom paste). Another kind of “paste layer” is a Gerber type file converted from PCB format files. Generally, PCB manufacturers also use Gerber for PCB production

Type of file. The specific resolution is also the suffix name, such as (TP, GTP or GBP, BP. They are the front patch layer and the back patch layer respectively).

Note: because our company first approved that if there is a paste layer, it should be made according to this layer. Then when placing an order, please check whether the pastes in the document are suitable for your use, and whether there are pastes that do not need to be tinned, but the pastes layer is designed, or need to be tinned

The position of the pad is not designed. At this time, you need to make notes, otherwise our company will not be responsible for the consequences.

2、 Anti tin bead process.

The function of anti tin bead process is to reduce the amount of tin and avoid the top material caused by excessive amount of tin on the pad. The common design method is to reduce the size of the original proportion of the pad. Usually, the pads that will make solder beads are large, and the size of a single pad is about 4mm or above

The situation will be divided into multiple pads. In another case, the anti tin bead process is mainly made of chip material facing the resistance and capacitance, which is designed into a “concave” shape according to the original proportion (for example, led, diode is not made, mainly because the two components require a large amount of tin for mounting)

Note: it is not absolute whether we need anti tin bead technology. Our definition of the scope of anti tin bead technology is mainly based on popular considerations. There may also be individual customers who may have less tin and false soldering due to this anti tin bead technology. Because we cannot know the production situation of each customer, we need customers to confirm whether they need it. The simplest way is to directly ask the chip processing factory. The main reasons are different printing machines and different debugging.

3、 Precautions for test points, solder joints and wiring arrangement.

TP type test points (including individual dots without characters) are not perforated by default, and solder joints and flat wires are perforated by default. Please note if there are special requirements

Note: TP type test points, that is, the silk screen tag number of PCB design drawings must be t or TP before they can be used as test points. Designing other pads with different tag numbers is not treated as a test point

Some customers may think that this definition is very narrow, but our company is not only facing local customers. When facing various design methods and habits, it is possible that the test point is solder joint and solder joint is test point. Therefore, our company can only define it in the most conventional way. May be large

Home thinks why our company doesn’t confirm with customers, because almost every model will have test points and solder joints in the design. This will delay our production time, that is, the time of customers, so we can only define the basic specifications first, and then make improvements later.

Warm tip: most customers who place orders will be unfamiliar with the products and unable to open the documents. In fact, new and old customers can consult the steel network customer service. In addition, they can also choose to submit the design drawings to the project to check whether there is a problem. In fact, a more direct method is to consult the chip OEM, because they know the production situation of the machine and have also used the experience of laser steel mesh. They are very familiar with the selection of steel mesh and steel sheet thickness and even the details of opening. Through such an ordered steel mesh, the qualification rate of steel mesh can be greatly improved.