Control Method of FPC Material Expansion and Shrinkage
FPC (Flexible Printed Circuit) refers to flexible circuit boards, also known as flexible printed circuit boards, or flexible boards.
The circuit board has the advantages of high wiring density, light weight and thin thickness. Widely used in mobile phones, laptops, PDA, digital cameras, LCM and many other products. In recent years, with the rapid development of PCB manufacturing technology, the industry has put forward higher requirements for FPC. Precision PITCH is the main breakthrough direction of FPC in the future. The stability and delicacy of size also lead to the rise of FPC cost. How to control the contradiction between the two has become a major breakthrough in the process of production. Next, we will give you a brief description of how to control and control the main points.
I. Design
1. Circuit: Because FPC expands due to temperature and pressure during ACF bonding, the finger expansion rate should be considered in the initial design of the circuit and pre-compensated.
2. Layout: The designed products are evenly and symmetrically distributed throughout the layout. The minimum interval between two PCS products is more than 2MM. The copper-free part and the porous part are separated as far as possible. These two parts are two important aspects which are affected by material expansion and shrinkage in the subsequent manufacturing process.
3. Material selection: the thickness of the covering film should not be too thin than that of the copper foil, so as to avoid the deformation of the product caused by insufficient filling when pressing, and whether the thickness and distribution of the adhesive are uniform or not, which is the main reason for the expansion and shrinkage of FPC materials.
4. Technological design: Cover all the copper foil parts as far as possible, do not recommend sticking the cover film, avoid uneven pressure when pressing, 5 MIL PI reinforcing veneer glue should not be too large, if unavoidable, it is necessary to press the cover film after drying and then PI reinforcing veneer pressing.
II. Material Storage
I don't need to say much about the importance of material storage. It should be stored strictly in accordance with the conditions provided by the material supplier. If it is refrigerated, it should not be sloppy.
III. Manufacturing
1. Drilling: It is better to bake before drilling to reduce the swelling and shrinking of the base plate during subsequent processing due to the high moisture content in the base material.
2. In electroplating, the short-side splint should be made to reduce the deformation caused by the water stress caused by the swing. The swing energy can be reduced to minimize the swing amplitude when electroplating. The number of splints also has a certain relationship. The number of asymmetric splints can be assisted by other edges.
When electroplating, the charged trough can avoid the impact of sudden high current on the plate, so as to avoid adverse effects on the plate electroplating.
3. Compression: The traditional press is more flexible than the fast press, the traditional press is constant temperature curing, the fast press is heat curing, so the change of the control glue of the traditional press should be stabilized, of course, the laminated platen is also a very important part.
4. Baking: For fast-pressing products, baking is a very important part. Baking conditions must be achieved so that the glue can be completely cured, otherwise there will be endless problems in subsequent production or use.
The baking temperature curve is generally gradually warmed up to the melting temperature of the glue, then continued until the glue is completely cured, and then gradually cooled down.
5. Maintain the stability of temperature and humidity in all workstations as far as possible during the production process, transfer between workstations, especially the need for outgoing production, the conditions of product storage need special attention.
IV. PACKAGING
Of course, the completion of the product is not to say that everything is all right, we need to ensure that customers do not have any problems in subsequent use. In packaging, it is best to bake first, dry the moisture absorbed by the base material in the manufacturing process, then use vacuum packaging, and guide customers how to preserve.
Therefore, in order to ensure the quality stability of this kind of products, it is necessary to preserve the materials, control the process, package, and strictly comply with the specific requirements before customers use them.
V. Concluding remarks
In the next few years, smaller, more complex and more expensive flexible circuits will require more innovative methods to assemble, and hybrid flexible circuits will be added. The challenge for the flexible circuit industry is to take advantage of its technological advantages to keep pace with computers, telecommunications, consumer demand and active markets.
