Common Quality Problems of Soldering Process and Improvement Measures
First, exposed copper
Clean room cleanliness did not meet the requirements
Screen, film or exposure glass or Mylar debris
Clean is not in place
WF screen printing room and exposure room shall reach 10,000, (1 cubic meter of space ≤ 0.5um dust ion to be ≤ 10,000. Weekly application of dust ion test to test.
The two doors of the transfer window can not be opened at the same time to prevent air convection.
Clean room must be a positive pressure state. Wash the screen version must be cleaned by more than three processes.
Net installed before the screen to check, if there is dry ink to be used to wash the net paper net wash wipe clean.
Solder Mask, Exposure Glass, Mylar Clean by SOP specification.
Use needle bed silk screen when the technician to confirm the above level, prevent needle bed scraping flowers.
Second, hole yellow
Plug hole is not full
Or silk screen when the orifice ink is thin
Plug hole ink does not allow the addition of thinner.
Selection of thixotropic better choice of ink plug hole oil.
For plates that do not allow holes yellow, plug holes ≥ 80% of the aperture diameter.
Plug hole ink viscosity control 300dpa.S above.
Green back to the wash board, the hole must vibrate through the ink before returning to the hole.
When installing the net alignment, with scrapped film, silk screen position adjustment accuracy. Plus the appropriate silk screen pressure production.
Earnestly check the first board, and independent inspection. Does not allow the phenomenon of plug hole deviation.
Plug the orifice plate must be within 15min silk screen finished oil. Can not be suspended for too long.
Third, SM but oil
Reason: The main screen printing parameters are not appropriate
Adjust the appropriate silk screen pressure, speed, ink viscosity.
Use a smooth blade without scraping, and adjust the appropriate blade angle of attack.
Adjust the appropriate blade slope, network distance.
Screen installed before the screen for careful and careful inspection.
Screen printing carefully when the first board check, and self-examination.
Use the appropriate network. Suitable squeegee hardness.
For the ink thickness has special requirements and copper thickness ≥ 2 / 2OZ board, according to the actual situation can change the screen printing method.
Fourth, the deviation
Staff not careful operation
Staff skills are not enough
When the first choice of easy to see PAD easy to locate.
Set a good position and then select the smallest 10 times, the most intensive SMT, SMD, BGA accurate alignment. And then use the rules of non-positioning of each U and each SET for careful examination of the more difficult bit board, select the skills of good staff alignment.
Film deformation of not more than 1miL, baking and cooling methods can be used to improve,
If you go beyond this range must cut the film for alignment, can not cut the film to apply for change of film coefficient.
Each pair of 30-50PNL board must be replaced once the single-sided adhesive. Because the outer layer has changed the film coefficient plate, solder mask alignment there is a shift phenomenon, to be matched with peach plate alignment. Be beyond the ability to work to be timely feedback to the boss.
Fifth, single-sided open the window plug hole green oil on the PAD
WF solder mask production process with a white net plug with India, the distance of the hole, and silk screen development caused by poor control.
Use better thixotropic ink plug hole oil.
Plug hole ink is strictly prohibited to add thinner.
Strictly according to the first surface of the first side of the screen to open the first screen, cover the second side of screen printing.
QC strictly do the first board inspection, such as found on the board developed out of oil on the PAD phenomenon immediately feedback process leader above the relevant personnel.
Switch to aluminum plug hole production (PH value control in the 10.8-11.5 between).
In the solder mask plus one-way than the hole 3miL small block point.
Developers must carefully examine the operator, such as found on the oil.
PAD phenomenon, immediately adjust the development speed control. After development, the retarder or UV curing is performed.
Plug hole method:
- Stop point network plug hole
Plug hole requirements are not strict, allowing part of the hole light, allowing the orifice copper color (ie hole yellow)
Hole diameter 0.3-0.35 hole.
- Aluminum plug hole
Strict hole requirements, does not allow the hole light, does not allow the copper hole color (ie, yellow)
HAL’s BGA board.
Inner hole, VIP hole (need to use a special resin ink.) Screen printing process pressure control in the 4-6kg / cm2, Aiguaizha control at 15-20 degrees, the general shovel knife screen printing, Degrees above the hard squeegee glue.
Six, green oil into the hole
The reason is:
Screen printing parameters are not adjusted properly
Normative homework is not in place
Responsibility is not enough
Beyond the scope of the process
Clean room temperature and humidity to be strictly controlled, temperature: 22 ± 2, humidity: 55 ± 5%. If abnormal heart to be timely feedback.
Screen printing before the computer must make clear instructions to clear the board then take the standard.
For ≤05mm aperture, but does not allow ink into the hole and the hole standard. Switch to block network production.
Ink thinner in strict accordance with the rules to add, non-standard operation is strictly prohibited. Normal screen printing, such as stopping halfway silkscreen 3-5min to be cable 2-3 sheets.
With white screen when the shift is not enough, there are stacked holes phenomenon. And silk screen printed 10 boards need to take white 1-2 sheets.
Use a smooth blade without scraping silk screen. Squeegee regularly grind. And to ensure that the plastic scraper thickness ≥ 10mm. If not meet the requirements must be promptly replaced.
Adjust the screen when installing the appropriate network distance: 4-6mm.
Adjust the appropriate screen printing speed, scraper angle, tilt. And do the first board inspection and independent inspection.
If the first board is not OK, redo the first board, the problem board must be reworked and logo, the first board OK before mass production, and conscientiously implement the self-test frequency. If there is an exception to be timely feedback.
For aperture ≤ 0.25mm, does not allow green oil into the hole by single-sided silk screen alignment / exposure production.
Silk screen should be arranged by hand to conduct random checks, and poor green oil into the hole statistics.
For the small batch of green oil on the PAD phenomenon, you can add baking 72 / 8min, and then back to red again, the development speed control 6-7m / min, the pressure: 2.0-3.0kg / cm2, under pressure: 0.8- 2.0kg / cm2.