A kind of preparation method of weighing instrument film key switch and its antistatic backing
Technical field
The present invention relates to a kind of weighing instrument film key switch and its preparation method of antistatic backing.
Background technology
Intelligent weighing instrument is very high due to the requirement of outward appearance, and conduct is switched through frequently with the film key with form in design
Operation carrier, while bringing easy to operate and elegant in appearance, also encounters antistatic problem, particularly weighing instrument
Table is high to display degree and exhibit stabilization requirement.When conventional films key switch is as guidance panel, because film key is opened
Close and there are some defects, one leaves substantial amounts of space in itself, and the shielding of this electron product and antistatic bring very big difficulty
Topic, secondly the circuit and component of switch sections are easily disturbed by radio frequency and electrostatic, causes the misoperation of button operation.Thirdly
Shielding processing cannot be carried out in the transparent window portion of display.If such thin film switch is applied directly in weighing instrument to be made
With antistatic interference is a problem.
The content of the invention
First purpose of the invention is to provide a kind of weighing instrument film key switch.
The technical scheme for realizing first purpose of the invention is a kind of weighing instrument film key switch, by printed circuit board (PCB)
Constituted with covering thin-film key panel on a printed circuit;
The printed circuit board (PCB) is followed successively by ground plane, bus plane and some signals layers from the bottom to top;If the ground plane with
ESD electrostatic impedors are connected between dry signals layer;
The thin-film key panel is from top to bottom followed successively by:First protective layer, antistatic backing, pet substrate, patterned layer,
Two protective layers, conductive adhesive layer and button bed course;In first protective layer, antistatic backing, pet substrate, patterned layer, the second protection
One transparent window is set on layer and conductive adhesive layer;The antistatic backing, pet substrate, patterned layer, the second protective layer and conducting resinl
At least one technique via is set on layer, antistatic backing and conductive adhesive layer are connected;
The ground plane of the printed circuit board (PCB) is connected with the antistatic backing of thin-film key panel.
The antistatic backing is electrically conducting transparent ink;First protective layer and the second protective layer are UV ink.
Each layer of the conductive adhesive layer area more than portion disposed thereon.
Second object of the present invention is to provide a kind of preparation method of thin-film key panel.
The technical scheme for realizing second purpose of the invention is a kind of preparation method of thin-film key panel, including following step
Suddenly:
Step one:Prepare PET base material, and the printing pattern layer in PET base material;
Step 2:Antistatic backing is made using silk-screen printing in the another side of PET base material;
A, the half tone equipped with antistatic backing pattern is changed on screen process press, the spacing of half tone and printing machine platform for 4~
5mm;
B, from scraper shore hardness be 70 degree of perpendicular type frictioning, be installed on screen process press doctor blade holder and half tone
Into 70 degree of angles;From 15~60dPas of viscosity, the electrically conducting transparent ink of sheet resistance value≤700ohm, in centrifuge with 1500 turns/
Minute stirring is used after 30 minutes, then operates the uniform electrically conductive ink that is bulldozed on half tone of the returning blade on screen process press to starch;
C, half tone take the PET sheet material that step one is obtained after rising, and diaphragm is placed in silk-screen printing machine table top down, using platform
Wind inlet on face holds PET, and is removed the dust of material surface with dedusting roller clean;
E, operation screen process press put down half tone, and mobile scraper, electrically conducting transparent ink slurry passes through the area of the pattern on half tone,
The pattern of antistatic backing is left on PET base material surface;
F, stopping air draught moving on to PET sheet material on 98 DEG C of conveyer belts of ± 2 DEG C of hot drying tunnels from printing table, pre- by 2min
It is placed into after drying and processing on net car;
G, the panel that will be molded send into 130 DEG C ± 3 DEG C of oven heat baking, wait 30min curing process;After heat cure
The surface of PET sheet material is the anti-quiet layer to be formed;PET base material front is that the thickness of full paving is 4um transparent conductive materials after heat cure
Antistatic backing.
The specific method of the step one is:Printing color ink obtains patterned layer in the thick PET base materials of 0.2mm, passes through
98 DEG C of ± 2 DEG C of hot drying tunnel 2.5min preliminary drying dry-cure are crossed, then the colored ink face cladding thickness in patterned layer is 0.06mm indigo plants
Color LK-820B diaphragms.
After employing above-mentioned technical proposal, present invention offers following beneficial effect:(1) present invention is using in bus plane
Between ground plane and connect TV power protections device come reduce moment generation electromagnetic interference, it is ensured that circuit element below from
The impact of transient state high-energy and damage, protect protection button thin film switch in itself.
(2) with conductive adhesive layer be connected antistatic backing by being arranged on multiple technique vias of button frame surrounding by the present invention,
It is connected with metal chassis by conductive adhesive layer again so that and equipment monolithic case forms a tight antistatic chamber, can reach
Maximum antistatic efficiency.
(3) present invention sets one layer of button bed course between printed circuit board (PCB) and thin-film key panel, can isolate conduction
Copper Foil signals layer on glue-line and circuit board.
(4) antistatic backing of the invention employs transparent conductive coating silk-screen in transparent window area, both meets viewfinder area
Display effect, while the efficiency of antistatic can also be reached.
(6) technique of the invention significantly reduces the manufacturing cost of film key switch, is suitable to produce in enormous quantities, can answer
For the EMI shieldings of Aero-Space, mine ocean and fine measuring instrument equipment operation key panel.
Brief description of the drawings
In order that present disclosure is easier to be clearly understood, it is right below according to specific embodiment and with reference to accompanying drawing
The present invention is described in further detail, wherein
Fig. 1 is the front view of film key switch of the invention.
Fig. 2 is the left view of Fig. 1.
Fig. 3 is circuit diagram of the invention.
In accompanying drawing marked as:
Printed circuit board (PCB) 1, ground plane 11, bus plane 12, some signals layers 13, thin-film key panel 2, the first protective layer
21st, antistatic backing 22, pet substrate 23, patterned layer 24, the second protective layer 25, conductive adhesive layer 26, button bed course 27, transparent window
28th, technique via 29, button 210.
Specific embodiment
(embodiment 1)
See Fig. 1 and Fig. 2, a kind of weighing instrument film key switch of the present embodiment by printed circuit board (PCB) 1 and is covered in print
Thin-film key panel 2 on printed circuit board 1 is constituted;If printed circuit board (PCB) 1 be followed successively by from the bottom to top ground plane 11, bus plane 12 and
Dry signals layer 13.Thin-film key panel 2 is from top to bottom followed successively by:First protective layer 21, antistatic backing 22, pet substrate 23, pattern
The 24, second protective layer 25 of layer, conductive adhesive layer 26 and button bed course 27;The first protective layer 21, antistatic backing 22, pet substrate 23,
One transparent window 28 is set on patterned layer 24, the second protective layer 25 and conductive adhesive layer 26;Antistatic backing 22, pet substrate 23, figure
At least one technique via 29 is set on pattern layer 24, the second protective layer 25 and conductive adhesive layer 26, by antistatic backing 22 and conducting resinl
Layer 26 is connected;Antistatic backing 22 is electrically conducting transparent ink;First protective layer 21 and the second protective layer 25 are UV ink.Conductive adhesive layer
26 areas more than portion disposed thereon each layer, for chassis contact.
See Fig. 3, ESD electrostatic impedors are connected between ground plane 11 and some signals layers 13;The ground plane of printed circuit board (PCB) 1
11 are connected with the antistatic backing 22 of thin-film key panel 2.The ground plane 11 of printed circuit board (PCB) 1, bus plane 12 and some signals layers
13 is all conductive, faces many interference, for signal line layer, using between holding wire and ground wire and connecing ESD static impedances
Device, on the surface of film key switch, due to touch effect, will produce electrostatic phenomenon;Due to electricity can be produced on button wire
Potential difference, can cause the device breakdown being connected on the lead to be damaged.Key switch panel is eliminated using ESD electrostatic impedors
Electrostatic effect, effect is fine.To be tried one's best in cloth holding wire and separate low-and high-frequency signal, modulus signal is separate, it is all kinds of to avoid
Signal is interfered.
Antistatic backing preparation method on thin-film key panel, is also the key of the present embodiment.Comprise the following steps:
Step one:Prepare PET base material 23, and the printing pattern layer 24 in PET base material 23;Specific method is:It is thick in 0.2mm
PET base material 23 on printing color ink obtain patterned layer 24, by 98 DEG C of ± 2 DEG C of hot drying tunnel 2.5min preliminary drying dry-cure, so
The colored ink face cladding thickness in patterned layer 24 is 0.06mm blueness LK-820B diaphragms afterwards;
Step 2:Antistatic backing 22 is made using silk-screen printing in the another side of PET base material 23;
A, the half tone equipped with antistatic backing pattern is changed on screen process press, the spacing of half tone and printing machine platform for 4~
5mm;
B, from scraper shore hardness be 70 degree of perpendicular type frictioning, be installed on screen process press doctor blade holder and half tone
Into 70 degree of angles;From 15~60dPas of viscosity, the electrically conducting transparent ink of sheet resistance value≤700ohm, in centrifuge with 1500 turns/
Minute stirring is used after 30 minutes, then operates the uniform electrically conductive ink that is bulldozed on half tone of the returning blade on screen process press to starch;
C, half tone take the PET sheet material that step one is obtained after rising, and screen layer 25 is placed in silk-screen printing machine table top down, utilize
Wind inlet on table top holds PET, and is removed the dust of material surface with dedusting roller clean;
E, operation screen process press put down half tone, and mobile scraper, electrically conducting transparent ink slurry passes through the area of the pattern on half tone,
The pattern of antistatic backing is left on the surface of PET base material 23;
F, stopping air draught moving on to PET sheet material on 98 DEG C of conveyer belts of ± 2 DEG C of hot drying tunnels from printing table, pre- by 2min
It is placed into after drying and processing on net car;
G, the panel that will be molded send into 130 DEG C ± 3 DEG C of oven heat baking, wait 30min curing process;After heat cure
The surface front of PET sheet material is that the thickness of full paving is the antistatic backing 22 of 4um transparent conductive materials.
Then antistatic backing 22 and conductive adhesive layer 26 are passed through into multiple technique vias 29 to be connected, then be bonded conductive adhesive layer 26,
Button bed course 27, you can form thin-film key panel, then carry out hot-forming treatment, forms button cavity space, thus lifts hand
Sense pressing effect, finally connects with printed circuit board (PCB) 1 and just obtained film key switch again.
Particular embodiments described above, has been carried out further in detail to the purpose of the present invention, technical scheme and beneficial effect
Describe in detail bright, should be understood that and the foregoing is only specific embodiment of the invention, be not intended to limit the invention, it is all
Within the spirit and principles in the present invention, any modification, equivalent substitution and improvements done etc., should be included in guarantor of the invention
Within the scope of shield.