Introduction to 9 common problems in PCB production

1. Whether the quality and thickness of PCB will affect the cooling effect?

The heat dissipation effect is mainly influenced by the circuit design, which determines the heat dissipation.

2. What kind of specifications are there in general? What kind of copper is recommended by PCB manufacturer?How to calculate the thickness after completion?

Copper thickness has HOZ, 1OZ, 2OZ, 3OZ, general products with HOZ, like automotive board, aerospace, military, communications generally use 1OZ copper thickness, to ensure its reliability, copper is electrolytic copper, purity of 99.9% or more, after the completion of the thickness section to read its thickness, the base material to the thickness of copper table.

3. Influence of copper wall thickness on PCB reliability? If the copper thickness at least how thick, in order to withstand reflow soldering, wave soldering, use in the process of hot and cold shock?How to evaluate a PCB as the recipient?

Evaluate its reliability according to IPC6010 standard.

4. How much is the minimum spacing between the perforated PAD and the window PAD? What is the minimum spacing required for a green oil bridge between SMT pads?What does the oil stop point mean?

A. The minimum spacing between the perforated PAD and the windowed PAD is greater than or equal to 4MIL;

B. In order to make green oil bridge between SMT pads, the minimum spacing of window pads needs 7.5mil;

C. The oil stop point is an oil free zone in the center of the hole.

5. What is the normal thickness of goldfinger? Is there a goldfinger PCB board, the entire PCB surface is treated as gold (including the finger), that is, the finger does not need additional gold plating?

A. the conventional thickness of goldfinger nickel is 2.54um and 0.5-0.75um respectively.

B. Yes, the whole board for nickel gold, if it is used in the words of more frequent, it is best to plated thick hard gold on the basis of gold, to meet the effect of wear resistance.

6. About the content of fire rating identification?

Flammability class UL94 is the most widely used standard for the flammability of plastic materials.It is used to evaluate the ability of a material to go out after it has been ignited.

HB: lowest flame retardant rating in UL94.A combustion rate of less than 40 mm/min is required for samples 3 to 13 mm thick;For samples less than 3 mm thick, the combustion rate is less than 70 mm/min;Or go out in front of the 100mm mark.

V-2: after two 10-second combustion tests on the sample, the flame is extinguished within 60 seconds.You can have something burning down.

V-1: after two 10-second combustion tests on the sample, the flame is extinguished within 60 seconds.No combustor can fall off.

V-0: after two 10-second combustion tests on the sample, the flame is extinguished within 30 seconds.No combustor can fall off.

7. About the spray tin plate, the window will be blocked phenomenon?

A. Opening the window on one side of the plug plate will block the tin

B. Tin can be bet for single side window opening with non-plug hole plate aperture less than or equal to 0.3mm

8. Why do the processed PCB and GERBER files sometimes not match?

This is mainly designed to the practical problems in the process, one is the problem of equipment, one is the impact of the environment, we want to make the product can meet the requirements, in the production process, to set compensation to reduce the impact of equipment and environment.

9. How to avoid the difference between the theoretical value and the measured value of characteristic impedance between microstrip line and differential line?

Microstrip line is related to line width, copper thickness, dielectric layer thickness and dielectric constant of sheet metal.As the copper thickness decreases, the impedance also increases.When the dielectric layer decreases, the impedance also decreases.When the dielectric constant decreases, the impedance increases.Which of these four factors affects the impedance more, then depends on their rate of change.

Common microstrip line design

Microstrip line (usually between 25 ohms and 70 ohms)

Line thick impedance requirement

5 mil ohms 60 + / – 10%

7 mil 50 ohms + / – 10%

18 ohms mil 28 + / – 10%

Characteristic impedance of difference line

• in addition to the same factors affecting the differential impedance as the single-line impedance, another very important factor is the very large influence of the line gap, which may sometimes be the largest influence.Generally speaking, the line bottom width decreases and the line gap increases, so the PE design impedance line is usually based on the line bottom, but the line side erosion is too large, there will be some impact, its principle is the same as the line width.

Differential line impedance design

Common double line impedance design

Line gap impedance requirements

5 mil 8 ohms mil 100 + / – 10%

4 ohms 14 mil mil 120 + / – 10%

All right, the above are the 9 common problems in PCB production, hope to help you ~ we are a PCB manufacturer in China, our products include: hard gold PCB, heavy copper PCB, etc., welcome to consult and purchase ~