Patent Application
20090176080
1. Technical Field
The present invention relates to flexible printed circuit boards, particularly to a stiffener and a strengthened flexible printed circuit board having the stiffener.
2. Description of related art
In recent years, electronic products have achieved miniaturization in volume and diversification in function. Flexible printed circuit boards (FPCBs) are widely used for electrical connection because of their flexibility and lightness.
Typically, a mass of electronic components are mounted onto a surface of a flexible printed circuit board to achieve various functions. For mounting and supporting the electronic components, a stiffener made of polyimide (PI) is usually attached onto the rear of the flexible printed circuit board via an adhesive layer to increase mechanical strength of the flexible printed circuit board, thereby obtaining a strengthened flexible printed circuit board. However, the strengthened flexible printed circuit board with the polyimide stiffener still has not enough mechanical strength to mount a mass of electronic components thereon. In addition, high cost of the polyimide stiffener may increase the cost of manufacturing the strengthened flexible printed circuit board.
What is needed, therefore, is a stiffener and a strengthened flexible printed circuit board having the stiffener so as to increase mechanical strength of the flexible printed circuit board and lower cost of manufacturing the flexible printed circuit board with high mechanical strength.
One present embodiment provides a stiffener. The stiffener includes at least one polyethylene naphthalate layer. The at least one polyethylene naphthalate layer is represented by the following general formula:
Another present embodiment provides a strengthened flexible printed circuit board. The strengthened flexible printed circuit board includes a flexible printed circuit board and a stiffener attached onto the flexible printed circuit board. The stiffener includes at least one polyethylene naphthalate layer. The at least one polyethylene naphthalate layer is represented by the following general formula:
Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Embodiments will now be described in detail below with reference to the drawings.
Referring to
The stiffener 20 has a thickness in a range from 25 to 250 microns. Thus, the stiffener 20 has adequate rigidity to increase mechanical strength of a flexible printed circuit board and has adequate flexibility to maintain flexibility of a strengthened flexible printed circuit board with the stiffener 20 for a roll-to-roll process.
The stiffener 20 is comprised of a polyethylene naphthalate (PEN) represented by the following general formula:
The polyethylene naphthalate can be prepared from ethylene glycol and one or more naphthalene dicarboxylic acids by condensation polymerization. The polyethylene naphthalate has a number of naphthalene rings in the molecular structure thereof. The naphthalene rings can increase rigidity of the molecular structure. Thus, the polyethylene naphthalate has good mechanical strength and structure stability. Moreover, coefficient of thermal expansion (CTE) for the polyethylene naphthalate is in a range from 18×10−6 to 20×10−6 K−1. In general, coefficient of thermal expansion for the polyimide is in a range from 18×10−6 to 28×10−6 K−1. Therefore, the polyethylene naphthalate has similar thermal expansion property to the polyimide, and has good thermal resistance and thermal stability. In addition, the polyethylene naphthalate has a lower cost than the polyimide. Cost of manufacturing the flexible printed circuit board with high mechanical strength can be reduced correspondingly.
The stiffener 20 can includes an adhesive layer adhered thereto. Additionally, a stiffener can include a number of polyethylene naphthalate layers and a number of adhesive layers arranged in an alternate fashion, thereby forming a multilayer structure to further increase mechanical strength of the stiffener.
Referring to
The polyethylene naphthalate layers 310 are represented by the following general formula:
The adhesive layer 320 can be comprised of a material selected from a thermoplastic adhesive and an ultraviolet-curable adhesive.
It is noted that the stiffener 30 can includes a number of polyethylene naphthalate layers 310 and a number of adhesive layers 320 arranged in an alternate fashion. The number of layers of the polyethylene naphthalate layers 310 is one greater than that of the adhesive layers 320. Each of the adhesive layers 320 is disposed between the two polyethylene naphthalate layers 310 adjacent thereto and is configured for adhering to the two polyethylene naphthalate layers 310. Thus, the stiffener 30 contains two polyethylene naphthalate layers 310 on two opposite outer sides thereof, respectively. Each of the two polyethylene naphthalate layers 310 on two opposite outer sides of the stiffener 30 is configured for adhering to the flexible printed circuit board. The total thickness of the stiffener 30 is in a range from 75 to 250 microns.
Referring to
Referring to
Referring to
It is noted that the stiffener 30, 40, 50 can be used as a substitute of the stiffener 20 of the strengthened flexible printed circuit board 60 so as to increase mechanical strength of the flexible printed circuit board 610.
Referring to
Referring to
It is noted that one adhesive layer 520 on the outer side of the stiffener 50 can adheres to a flexible printed circuit board, another adhesive layer 520 on the outer sides of the stiffener 50 can adheres to other component such as a rigid printed circuit board, a support and an electronic component.
It is also note that the stiffener 20, 30,40, 50 can be used to adhere to other flexible substrates such as a flexible copper and a copper clad laminate to increase mechanical strength of the flexible substrates. Thus, due to the strength of the flexible substrates is increased, processing of the strengthened flexible substrates become easy.
While certain embodiments have been described and exemplified above, various other embodiments will be apparent to those skilled in the art from the foregoing disclosure. The present invention is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 097100306 | Jan 2008 | TW | national |
