One. Frame

The size of the printing press is different, and the size of the frame will be different. Therefore, the size of the specific frame depends on the printing machine. Commonly used frame recommended models: 370 × 470mm, 400 × 500mm, 600 × 550mm, 650 × 550mm, 300 × 400mm and so on.

two. Steel sheet

1. Steel sheet thickness (thickness can be 0.1mm-0.3mm)

(1) In order to ensure sufficient tin/glue quantity and welding quality, the recommended thickness of steel sheet is 0.18mm for printing net and 0.15mm for tin printing net;

(2) If there are important devices (such as qfp, csp, 0402, 0201, cob, etc.), in order to ensure the amount of tin and the quality of the solder, the choice of the thickness of the tinplate is more important.

2. Steel sheet size

In order to ensure sufficient tension and good flatness of the steel mesh, it is generally recommended that the steel sheet be kept 20 to 30 mm from the inner side of the frame.

three. Mark Stippling Method Depending on the customer's printing machine, there are half of the printing surface, half of the non-printing surface, two sides and a half of the engraving, full-sealing black rubber and all-in-one black rubber.

four. The characters are convenient to distinguish the type of steel mesh suitable for production, the use status and communication with customers. It is generally recommended to engrave the following characters on the steel net: customer model (model), factory number (p/c), steel sheet thickness (t), date of manufacture (date).

Fives. Open general rule

1. Test point, separate pad, no opening if the customer has no special instructions.

2. Chinese characters have no special requirements.

six. Opening method

(1) Printing tinplate

Opening design of 1chip material components

(1) The pad opening of package 0402 is 1:1;

(2) Packaged as 0603 and 0603 chip components.

2 small shape crystal opening design

(1) sot23-1: Since the size of the pads and components are relatively small, the probability of producing solder balls and short circuits is small. To ensure the soldering quality, it is generally recommended to press 1:1.

(2) sot89 crystal: Since the pads and components are relatively large, and the pad pitch is small, it is easy to produce soldering quality problems such as solder balls. Therefore, it is generally recommended to use the opening shown in the following figure:

(3) sot143: The pitch of the pad distribution is relatively large, and the probability of occurrence of solder quality problems is small, so it is generally recommended to open in a 1:1 manner.

(4) The sot223 crystal opening is usually recommended in a 1:1 manner.

(5) sot252 crystal opening design: Since the sot252 crystal has a large pad, it is easy to produce tin beads.

3 ic (soj, qfp, sop, plcc, etc.) opening design:

(1) pitch > 0.65mm ic length according to the original pad 1:1 opening, width = 50% pitch, four corners rounded.

(2) ic with pitch ≤ 0.65mm, because of its small pitch, it is easy to cause welding quality problems such as short circuit and bridge, so its opening method: length 1:1, rounded, width (45%~50%) pitch .

4 exclusion opening design:

(1). pitch=0.5, length plus 0.05, width 0.24mm or 48% pitch, pitch increased by 0.05mm.

(2). pitch=0.8, long press 1:1, inner four feet wide open 0.4mm, outer four feet maximum not more than 0.55mm.

(3). Other pitch exclusion openings have a width of 55% pitch.

5 bga opening design: usually in a 1:1 opening. Can increase the diameter by about 25% on the original basis.

6 Common pad opening design: It is recommended to press 1:1 opening.

7 Special pads: 1:1 openings are recommended for pads not described above. If the pads are large, 90% of the open area can be used.

8 Other requirements: If a pad is too large (usually one side is larger than 4mm and the other side is not less than 2.5mm, in order to prevent the generation of tin beads, the mesh opening is usually recommended to use grid line segmentation, grid line width It is 0.4mm and the grid size is about 3mm, which can be equally divided by the pad size.