Microwave Tech - 14 precautions for high-frequency circuit board processing?

Regardless of the internal quality of high-frequency circuit boards, they are almost the same on the surface. We have to look through the surface to see the differences, and these differences are critical to the durability and functionality of the PCB high-frequency board throughout its life. Whether it is in the manufacturing assembly process or in actual use, it is essential that high-frequency circuit boards have reliable performance. In addition to related costs, defects in the assembly process may be brought into the final product by the high-frequency circuit board, and failures may occur during actual use, leading to claims. Therefore, from this point of view, it is no exaggeration to say that the cost of a high-quality high-frequency circuit board is negligible. These aspects should be kept in mind when comparing the processing prices of high-frequency circuit boards. So, do you need to know these 14 precautions for high-frequency circuit board processing?

1. Copper thickness of 25 micron hole wall of high frequency circuit board

Benefits: Enhance reliability, including improving the expansion resistance of the z-axis.

Risks of not doing this: blow holes or outgassing, electrical connectivity problems during assembly (inner layer separation, hole wall breakage), or failure under load conditions during actual use. IPCClass2 (the standard adopted by most factories) requires 20% less copper plating.

2. Exceed the cleanliness requirements of IPC specifications

Benefits: Improving the cleanliness of high-frequency circuit boards can increase reliability.

Risk of not doing so: Residues and solder accumulation on high-frequency circuit boards bring risks to the solder mask. Ionic residues can cause corrosion and contamination risks on the soldering surface, which may lead to reliability problems (bad solder joints/electrical failures), And ultimately increase the probability of actual failure.

3. The tolerance of the copper clad laminate meets the requirements of IPC4101ClassB/L

Benefits: Strictly controlling the thickness of the dielectric layer can reduce the deviation of expected electrical performance.

The risk of not doing this: the electrical performance may not meet the specified requirements, and there will be large differences in output/performance of the same batch of components.

4. Defining the tolerances of shapes, holes and other mechanical features

Benefits: Strict control of tolerances can improve the dimensional quality of products-improve fit, shape and function

The risk of not doing this: problems in the assembly process, such as alignment/fitting (only when the assembly is completed will the press-fit needle problem be found). In addition, due to the increased size deviation, there will be problems when installing into the base.

5. Use internationally renowned substrates-do not use "local" or unknown brands

Benefits: Improve reliability and known performance.

The risk of not doing so: Poor mechanical performance means that the circuit board cannot perform the expected performance under assembly conditions, for example: high expansion performance will cause delamination, disconnection and warpage problems. Weakened electrical characteristics can lead to poor impedance performance.

6. Repair without welding or open circuit repair

Benefits: perfect circuit can ensure reliability and safety, no maintenance, no risk

The risk of not doing so: If the repair is not done properly, it will cause the high-frequency circuit board to open. Even if the repair is ‘proper’, there is a risk of failure under load conditions (vibration, etc.), which may cause failure in actual use.

7. Define solder mask materials to ensure compliance with IPC-SM-840ClassT requirements

Benefits: Excellent ink can achieve ink safety and ensure that the solder mask ink meets UL standards.

The risk of not doing so: Inferior ink can cause adhesion, flux resistance and hardness problems. All these problems will cause the solder mask to separate from the circuit board and eventually lead to corrosion of the copper circuit. Poor insulation properties can cause short circuits due to accidental electrical continuity/arc.

8. Strictly control the service life of each surface treatment

Benefits: solderability, reliability, and reduce the risk of moisture intrusion.

The risk of not doing this: due to the metallographic changes in the surface treatment of the old circuit boards, soldering problems may occur, and moisture intrusion may cause delamination, inner layers and hole walls during the assembly process and/or actual use Separation (open circuit) and other issues.

9. Requirements for the thickness of the solder mask, although IPC does not have relevant regulations

Benefits: Improve the electrical insulation properties, reduce the risk of peeling or loss of adhesion, and strengthen the ability to resist mechanical impact-no matter where the mechanical impact occurs!

The risk of not doing this: thin solder mask can cause adhesion, flux resistance and hardness problems. All these problems will cause the solder mask to separate from the circuit board and eventually lead to corrosion of the copper circuit. Poor insulation properties due to the thin solder mask can cause short circuits due to accidental conduction/arc.

10. Defined appearance requirements and repair requirements, although IPC did not define

Benefits: Careful care and carefulness in the manufacturing process create safety.

The risk of not doing this: a variety of scratches, minor damage, repair and repair of high-frequency circuit boards can be used but not good-looking. In addition to the problems that can be seen on the surface, what are the invisible risks, the impact on assembly, and the risks in actual use?

11. Implement specific approval and order procedures for each purchase order

Benefits: The implementation of this program can ensure that all specifications have been confirmed.

The risk of not doing this: If the product specifications of the high-frequency circuit board are not carefully confirmed, the resulting deviation may not be discovered until the assembly or the final product, and it will be too late at this time.

12. Specify the brand and model of peelable blue glue

Benefits: The designation of peelable blue glue can avoid the use of "local" or cheap brands.

Risk of not doing so: Inferior or cheap peelable glue may blisters, melt, crack or solidify like concrete during the assembly process, making the peelable glue unable to peel off/not working.

13. Requirements for the depth of the plug hole

Benefits: High-quality plug holes for high-frequency circuit boards will reduce the risk of failure in the assembly process.

The risk of not doing so: The chemical residue in the gold deposit process can remain in the hole that is not full of the plug hole, which will cause problems such as solderability. In addition, there may be tin beads hidden in the holes. During assembly or actual use, the tin beads may splash out and cause a short circuit.

14. Do not accept boards with scrapped units

Benefits: Not using partial assembly can help customers improve efficiency.

The risk of not doing this: all defective boards require special assembly procedures. If it is not clear to mark the scrap unit board (x-out), or if it is not isolated from the board, it is possible to assemble the board. Known bad board, thus wasting parts and time.

iPCB® is mainly engaged in high-frequency microwave radio frequency circuit board and double-sided multilayer circuit board proofing and small and medium batch processing services. The main products are PCB circuit boards, Rogers circuit boards, high frequency circuit boards, high frequency microwave circuit boards, microwave radar antenna boards, microwave radio frequency high frequency boards, microstrip circuit boards, antenna circuit boards, heat dissipation circuit boards, high-speed circuit boards, Rogers/Rogers high-frequency board, ARLON high-frequency circuit board, mixed dielectric laminate, special circuit board, F4B antenna board, antenna ceramic board, radar sensor circuit board, etc. The company's products are widely used in communications, power supplies, medical equipment, industrial control, automotive electronics, intelligent equipment, and security electronics.