SMT solder paste printing standards and common defects include: less tin, tin connection, sharpening, displacement, missing printing, excessive tin, collapse, dirty PCB, etc. The thickness of solder paste printing is -0.02mm～+0.04 of the thickness of the steel mesh mm;

 

 

 

SMT solder paste printing standard

 

1. CHIP component printing standard

1. No offset of solder paste;

2. The amount and thickness of solder paste meet the requirements;

3. Solder paste molding is good. No collapse and fracture;

4. Solder paste covers more than 90% of the pad.

 

2, CHIP component printing allows

1. There are shrinkage cavities in the opening of the stencil, but 85% of the solder paste still covers the pad;

2. The amount of solder paste is uniform;

3. The thickness of the solder paste is within the required specification

4. Printing offset is less than 15%

 

3. Rejection of CHIP component printing

1. Insufficient amount of solder paste.

2. The amount of solder paste at two points is uneven.

3. Solder paste printing offset exceeds 15% of the pad

 

4. SOT component solder paste printing standard

1. No offset of solder paste;

2. The solder paste completely covers the pad;

3. The three points of solder paste are uniform;

4. The thickness of the solder paste meets the test requirements.

 

5. Solder paste printing for SOT components is allowed

1. The amount of solder paste is uniform and the shape is good;

2. More than 85% of the solder paste covers the pad;

3. The printing offset is less than 15%;

4. The thickness of the solder paste meets the specification requirements

 

6. SOT component solder paste printing rejection

1. More than 85% of the solder paste does not cover the pad;

2. Severe tin deficiency

 

7. Diode and capacitor solder paste printing standards

1. Solder paste printing is good;

2. Solder paste printing without offset;

3. Solder paste thickness test meets the requirements;

 

8. Solder paste printing for diodes and capacitors is allowed

1. The amount of solder paste is sufficient;

2. Solder paste covers more than 85% of the pad;

3. Good solder paste forming;

4. The printing offset is less than 15%.

 

9. Rejection of diode and capacitor solder paste printing

1. More than 15% of the pad is not completely covered by solder paste;

2. Solder paste offset exceeds 15% of the pad

 

10 Pad pitch=1.25-

0.7MM solder paste printing standard 1. Each solder paste covers 100% of each pad;

2. The amount of solder paste is uniform and the thickness is within the test range;

3. The solder paste is well formed, without tin deficiency or collapse;

4. No offset phenomenon.

 

11 Pad pitch=1.25-0.7MM Solder paste printing is allowed

1. The solder paste is well formed, the component solder feet are full, no collapse, no bridging;

2. There is an offset, but not more than 15% of the pad;

3. The thickness test of solder paste meets the requirements;

4. There is no defect in welding after furnace.

 

12. Pad spacing=1.25-0.7MM Solder paste printing rejection

1. More than 15% of the solder paste does not cover the pad;

2. The deviation exceeds 15%;

3. The solder paste almost covers two pads, which is easy to cause a short circuit after the furnace;

4. Solder paste printing forms bridges.

 

13. Pad spacing = 0.65MM solder paste printing standard

1. The solder paste printing of each pad covers 100% of the pad;

2. Solder paste is well formed, no collapse, no offset, no bridging phenomenon;

3. The thickness of the solder paste meets the requirements.

 

14. Pad spacing = 0.65MM solder paste printing is acceptable

1. The solder paste is well formed, without bridging or collapse;

2. The solder paste thickness test is within the specifications;

3. The offset of solder paste at each point is less than 10% of the pad.

4. There is no defect in welding after furnace.

 

15, Pad spacing = 0.65MM Solder paste printing rejection

1. More than 10% of the solder paste does not cover the pad;

2. The deviation exceeds 10%;

3. The solder paste almost covers two pads, which is easy to cause a short circuit after the furnace;

 

16. Pad spacing ≤ 0.5MM solder paste printing standard

1. The solder paste printing of each pad covers 100% of the pad;

2. The solder paste is well formed without collapse;

3. The thickness of the solder paste meets the requirements

 

17, Pad pitch ≤ 0.5MM Solder paste printing is acceptable

1. Although the solder paste forming is slightly poor, the solder paste thickness test is within the specification;

2. There is no offset, no bridging, and no collapse of the solder paste at each point;

3. There is no less tin and false soldering phenomenon after the furnace.

 

18. Pad spacing ≤ 0.5MM Solder paste printing rejection

1. The solder paste is poorly formed and broken;

2. Solder paste collapse and bridging;

3. Solder paste coverage is obviously insufficient.