For the electronics assembly industry, SMT assembly is a fairly mature process technology, but maturity does not mean that there are no defects. Conversely, with the further miniaturization of electronic component packaging, process issues become more difficult to control. According to authoritative statistics, the most important and critical process in the SMT process should be the solder paste printing process. Almost 70% of the solder defects are caused by poor solder paste printing.

The solder paste printing process is related to the success or failure of SMT assembly quality. The design and manufacture of steel mesh is a key factor in the quality of solder paste printing. The design can be used to obtain good solder paste printing results, otherwise the process quality will be unstable. The defect problem is difficult to control. The following is to show you the design of Linchuan Precision's common electronic components:

1, CHIP material components

The package is a rounded corner of the 0201 component that is 10% in the long direction and has an R=0.03mm. Gap guarantee must not be less than 9 MIL greater than 11 MIL

The package is 0402 component opening as shown in the figure (when the gap is less than 0.4mm, it needs to be moved to 0.4mm, and when the gap is larger than 0.4mm, it needs to be expanded to 0.4mm)

The package is 0603 component opening as shown in the figure (when the gap is less than 0.6mm, it needs to be moved to 0.6mm, when the gap is greater than 0.72mm, it needs to be expanded to 0.72mm)

                            

The package opening of the package 0805 or higher (including 0805) is as follows:
             　　      


FUSE.MELE opening is as follows:
                        　　    
 

The large CHIP material cannot be classified by 90% of the area of the pad, and the amount of tin in the component is adjusted slightly.

The diode is open at 100% of the pad area. If it is cylindrical, increase the length to ensure a sufficient amount of tin.

Generally, the PITH value of the component is combined with the standard pad size. For the standard, please refer to the following figure:                                                                                                                                                                         

2, small form factor crystal

SOT23: The pad size is small, to ensure solder quality, the hole is pressed to the pad.1:1.

SOT89: Use the hole opening method as shown below.

           　　
    
3, SOT252, SOT223 and other power transistor opening methods are as follows:
       

4, SOPSOJ socket connector and other components of the stencil opening design

PITCH=0.8-1.27mm, W.L is 1:1, and rounded at both ends (the width is generally between 45% and 60%)

PITCH=0.635-0.65mm, W=0.32mm, L is 1:1 and rounded at both ends.

PITCH=0.5mm, W=0.24mm, L is 1:1 and rounded at both ends.

PITCH=0.4mm, W=0.19mm, L is moved outward by 0.1mm, then lengthened outward by 0.05mm and rounded at both ends.

PITCH=0.3mm, W=0.16mm, L is 0.1mm outward, and rounded at both ends (if the length is <0.8mm, the length is 0.15mm long).

0.5PITCH QFP, 0.23mm in the width direction, 0.1mm in the length direction, and 0.1mm in the outer direction;

0.5PITCH QFN, 0.23mm in the width direction and 0.1mm in the length direction;

The silk screen frame is QFN from the pin, as shown in the following figure;

If L < 1 mm above, the L needs to be outwardly expanded by 0.1 mm. If the original size of W is smaller than the value of the value, it should be increased when opening.

5. If the IC is grounded, it needs to be opened:

The grounding pad in the middle is opened by 60% of the area, and if necessary, the bridge is rounded and rounded with R=0.05mm;

6, exclusion, discharge capacity (such as for the same customer, in the production: W should be unified):

The width is 48-50% of PITCH, L is 1:1 according to file and rounded at both ends.

If the pin is <0.8mm, the length is 0.15mm outward. If the gap between the two rows of pins is <0.4mm, the outward movement of each side ensures that the inner gap is 0.4mm.

7, BGA opening:

 BGA openings can be made with the following references:

A, in principle, the CIR of the opening is 55% of the PITCH, and if it is SQ, it takes 45% of the PITCH and the R=0.02mm round (except PITCH=0.5mm);

 B, PITCH=0.5mm, CIR=0.30mm or SQ=0.29mm, inverted R=0.02mm fillet;

 C, large BGA opening is divided into three circles, inner ring, inner ring and central part (large BGA distinguishing conditions: Pitch ≥ 1.27mm, number of feet ≥ 256): outer three circles CIR = 0.55 × Pitch, center part 1:1 Opening

8. When one side of the pad is ≥ 4mm and the other side is ≥ 3mm, the pad should be bridged with a bridge width of 0.4mm.

9. Avoid the through hole when the document has a shield:

Be sure to bridge at the corner, a straight bridge with a width of 0.5mm, and the rest of the length should not exceed 4mm bridge, the bridge width is 0.5mm. The width is extended outward by 0.2mm, and a safety distance of 0.3mm must be ensured with the peripheral pads.

10, electrolytic capacitor:

The length is plus 0.2mm (this type is not used for bridging if there is no special requirement during production)

11, the way of opening the cable is the same as the modification of the IC.

12, SIM card and TF deck smt steel mesh opening design:

          　　  
The outer three sides are outwardly lengthened by 0.25 mm, and the length of the pin on the right side is expanded by 0.25 mm in the direction of the arrow. If the width is small, the length can be appropriately increased.

Printing through rate

Independently developed on-line electrolytic polishing technology, not only safe and environmental protection, but also make SMT printing high through rate: 99%-99.7%.

Non-electropolishing or traditional polishing not only pollutes the environment, but also makes the printing pass-through rate low: the pass-through rate is less than 97%.

Shift qualitative

The technical team has rich experience and complete testing equipment. Each steel mesh undergoes six testing procedures.

Team instability, no other testing equipment except magnifiers, product shipment sampling or "exemption from inspection"

Electropolishing

Independent research and development of online electrolytic polishing technology, safety and environmental protection

No electropolishing or traditional polishing, polluting the environment, does not meet the requirements of environmental protection.

Technical service

Relying on the company's technology, optimizing the design scheme of customer opening to avoid design risks for customers

Only according to customer documentation production, can not provide any technical services for customers

Cost performance

Purchasing steel mesh is to create value for the company: SMT steel mesh value = steel mesh price - cost saved without repairs - order value increased with customer satisfaction

Purchasing steel mesh adds a lot of intangible costs to the company: SMT steel mesh value = steel mesh price + increased cost of repairs + customer dissatisfaction with the value of canceling orders

R&D capability

Research and development of next generation products, when customers have orders, can quickly help customers create value, enhance customer market competitiveness.

Unable to adapt to the times to update products, so that both their own and customers lose market competitiveness, to bring immeasurable losses to customers.