Description of the problem: 

The lamination process of the soft and hard bonding board is highly demanding. Any minor alignment deviation may lead to circuit breakage or short circuit. Particularly in the design of multilayer boards, the alignment accuracy between layers directly affects the circuit's connectivity. Sub-standard alignment accuracy will not only reduce the product's reliability but also might cause serious quality issues, resulting in batch scrapping.

Description of details: 

During the lamination process, due to the dissimilar coefficients of thermal expansion of the materials, different degrees of expansion may occur in each layer of materials during the heating process, causing alignment deviation. For instance, in one production run, as a result of improper setting of the lamination temperature, a layer of the soft and hard bonding board material expanded by 0.1mm. This minuscule expansion is magnified in the multilayer board design, ultimately causing a short circuit. Specifically, during the circuit test after lamination, it was discovered that a key signal line was blocked, and after microscopic examination, it was found that a certain section of the line overlapped with the wire of the adjacent layer due to the alignment deviation, forming a short circuit.

Refined Solutions:
1. Optimization of material selection and matching:

• Detailed implementation: When choosing materials, attempt to select PI and FR4 materials with similar thermal expansion coefficients to minimize the difference in expansion during heating. For example, through experimental comparison, a material combination with a thermal expansion coefficient within 50 ppm/℃ is selected to ensure that the expansion degree of each layer of material is similar during the lamination process.

2. Precise temperature control:

• Detailed implementation: Employ high-precision temperature control equipment to ensure uniform and stable temperature during lamination. For example, utilize a laminator equipped with a multi-point temperature sensor, monitor the temperature in different areas in real time, and precisely adjust it through a PID control system to ensure that temperature fluctuations are controlled within ±2 ° C.

3. Pre-alignment and compensation technology:

• Detailed implementation: Conduct pre-alignment before lamination and utilize a high-precision optical alignment system to ensure that the alignment accuracy of each layer material before lamination reaches ±0.01mm. Simultaneously, based on the thermal expansion characteristics of the material, design a certain amount of compensation in advance to offset the expansion effect during the heating process.

4. Optimization of laminating process parameters:

• Detailed implementation: Determine the optimal laminating temperature, pressure, and time parameters through experiments. For example, through multiple tests, determine the combination of process parameters with a laminating temperature of 180 ° C, a pressure of 50 kg/cm², and a time of 60 minutes, which not only ensures the full combination of materials but also minimizes the alignment deviation caused by thermal expansion.

5. Online monitoring and real-time adjustment:

• Detailed implementation: Implement online monitoring during the lamination process, collect key process parameters such as temperature and pressure in real time, and conduct real-time analysis through the data analysis system. Once the parameters are found to deviate from the set range, adjust them immediately. For example, install a real-time monitoring system to monitor the temperature during the lamination process in real time, and once the temperature is found to exceed the set range, automatically adjust the heating power immediately to ensure temperature stability.

6. Post-processing inspection and correction:

• Detailed implementation: After the lamination is completed, carry out strict X-ray inspection and microscopic inspection to ensure that the alignment accuracy of each layer of materials meets the requirements. For the alignment deviation identified, employ laser correction technology for local correction to ensure the connectivity and reliability of the circuit.

Case sharing: In a production instance, through the aforementioned refined solutions, the issue of alignment accuracy in the laminating process was successfully addressed. Specific operations are as follows:
• Material selection: Select PI and FR4 materials with similar thermal expansion coefficients to ensure a minimal expansion difference.
• Temperature control: Utilize high-precision temperature control equipment to ensure uniform and stable lamination temperature.
• Pre-alignment and compensation: Conduct pre-alignment before lamination and design a compensation amount of 0.05mm.
• Optimization of process parameters: Determine the optimal laminating parameters through experiments.
• Online monitoring: Real-time monitoring of temperature, pressure, and other parameters to ensure process stability.
• Post-processing inspection: Conduct X-ray inspection and microscopic inspection after lamination, and perform laser correction when alignment deviation is found.
Through these refinement measures, the alignment accuracy in the lamination process was significantly enhanced, the circuit short circuit problem was effectively resolved, and the product pass rate was increased by 15%.

Conclusion: Although the issue of alignment accuracy in the laminating process is complex, product quality and production efficiency can be effectively improved through meticulous management and technological innovation. It is hoped that the sharing of this article can provide some useful references for industry colleagues to jointly promote the advancement of soft and hard board manufacturing technology.