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PCB Assembly For Fingerprint Identification System

PCB Assembly For Fingerprint Identification System
Issue Time:2018-07-17

Fingerprint Identification System is made up by two PCB board with the same size, and are assembled in same cast to work together. This project is from a France customer, and now we are making prototype,we should firstly pass the test, then start mass production.


Currently, there are three types of fingerprint acquisition devices commonly used in the market: optical, silicon chip, and ultrasonic.This project is optical one.The optical fingerprint collector is the earliest fingerprint collector and is currently the most commonly used. It has the following advantages:

1 The longest time to use, subject to the actual use of the test

2 good adaptability to environmental factors such as temperature

3 The price is relatively low, and the resolution is higher, reaching more than 500 dpi.


At present, collectors that replace prisms and lens systems with grating lenses have also appeared, and photoelectrically converted CCD devices have also been replaced with CMOS imaging devices, thereby omitting the image acquisition card and directly obtaining digital images.


The PCB boards are TG140, 1.0mm thickness,1oz copper thickness,surface finishing HASL,2 layers,solder mask green, silk print white,size is 100mm*150mm.We produce the PCB by panel in order we do assembly work, the panel with V-CUT. After assembling, we will send the PCB by pieces, grind the PCB board edge, then package them ship out.


There are more than one hundred kinds of components,and it has been the newest one, the BOM provided with many corrections and notes, we must be very carefully to check each components, the package,value,part No.,accuracy...All the LEDs must 5mm higher than PCB board,the resistor accuracy must be 1% rather than 5%.The PCB are two side solder with both SMD and DIP components.Some components at the edge of the board are easily bad welded,as the pads are a little small and the components are so big,Subtle deviation of silk screens or pads can lead to poor soldering easily. So our engineer make the pads 1-2mm bigger, after this change, the components 100% well soldered. As this system is made up by two PCB board, with same size, so we must pay attention of height of each components, too high will let these 2 board can not fixed to each other, then assembled in housing case.

PCBA Board

The most important step is test. At this step, we may face many problems and solve them.This is a key and core link to future mass production,this can ensure that future mass production can be carried out smoothly.


The test material all provided by customer.We have a list of test material.

1:Laboratory power supply or mains unit (12VDC / 500mA min) with jack.

2:Digital voltmeter + red and black banana plug cords (Ø = 4 mm)

3:Carpet + antistatic wrist strap

4:ES board test bench

INSTALLATION OF THE TEST BENCH

1 Test bench switch on OFF (orange jumper removed) 

2 Set the power supply on + 12V and connect it to a board "Plug terminal block" (via jack) 3 Turn on digital voltmeter and connect to lugs + 5V (red) and 0V (black) of test bench. 

TEST PROCEDURE

1 Switch on OFF (orange jumper removed) 

2 Insert ES board to test on test bench 

3 Connect cable to RJ9 (J2) 

4 Insert the 2 “plugs terminal" on the ES board terminals bloks. 

5 Check voltage reading on voltmeter: + 5V (+/- 0.1V) 

6 Switch ON (orange jumper set) 

7 Press the TSW micro-switch and check the test sanction (see below)

 8 Position the SW485 switch on the other side then redo previous step.

9 Switch on OFF (orange jumper removed) 

10 Remove the 2 « terminal plugs » 

11 Remove RJ9 cable (J2) 

12 Remove the ES board and put in the OK or KO tray according to the sanction.

ANCTION OF THE TEST

Board OK: The LED is green on the UC card and on the plug terminal block board.

Board Ko: The led is red on the UC board and/or on the plug terminal board.

PCBA



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