The relationship between the design of screen printing nail

2018-12-04 14:56Writer: qyadminReading:
       Along the way of PCB soldermask production, the create of PCB constant double-side printing water soldermask by silkscreen printing nail-bed has been massively applied. Since relatively big variations happen between PCBs in conditions of areas of design including thickness, design distribution, via diameter and via distribution, the production of silkscreen printing nail-bed is incredibly difficult. If the distribution of copper fingernails on nail is definately not being affordable, soldermask thickness uniformity is easily triggered. The bad result is either the colour aberration of soldermask appearance, bad soldermask imaging or solder bridge with damaged resistance, resulting in rework or scrap. Therefore, comprehensive instructions need to be founded to pertain to toenail welding along the way of soldermask silkscreen printing to be able to guarantee the quality of nail.

  Theory Analysis

  Soldermask with double-side silkscreen printing identifies the process where water soldermask is imprinted on one part of PCB prior to water soldermask printing on the other hand using silkscreen printing nail. Therefore, constant printing of soldermask for both edges of PCB can be applied so that dwell time and heating system time can be reduced to boost circuit board production efficiency.

  To produce silkscreen printing nail, supporting fingernails should be deployed at where the bottom table of nail works with with PCB panel advantage or via positions. The difficulty of production process leads to relatively high dependence on technology, so that it needs to be completed by experienced employees who still possibly have problems with errors in conditions of insufficient fingernails welding, low toe nail distribution density, and position deviation of toenail distribution when they may be working with highly-complicated planks or planks with new type model.

  Therefore, it's essential to analyze the impact on PCB soldermask printing triggered by silkscreen nail with different toe nail distribution density so that sensible toenail distribution of soldermask silkscreen printing nail regulations can be acquired to increase nail production efficiency and the double-side silkscreen printing quality of soldermask.


  Test Design

  • Test factors and horizontal design

  For three types of toe nail distribution density (spacing 5.0cm, 8.0cm, 10.0cm) and PCB thickness (0.8mm, 1.5mm, 2.0mm).

  • Nail manufacturing

  A bare copper plank with the dimension of 457mmx610mm is applied as the nail base plate which copper fingernails are evenly positioned in the setting of array with green clear tapes set. Spacing between copper fingernails is respectively 5.0cm, 8.0cm and 10.0cm. Around the nail with different toenail distribution spacing, the length between external fingernails and the advantage of bottom table should be symmetrical vertically and horizontally to ensure that thickness distinctions won't happen because of the incorrect positions of copper fingernails along the way of silkscreen printing.

  Take the spacing of 5cm for example. The space of shorter aspect of copper panel is 45.7cm with 9 fingernails positioned on each row and 2.8cm horizontal clearance while 11 fingernails are positioned on each row along the longer part of the copper plank. Last but not least, 99 fingernails are required.

  • Test table manufacturing

  Bare copper panel with how big is 17''by23'' is applied with the thickness of plank 0.8mm, 1.5mm and 2.0mm. Each kind of planks with different thickness should discover 6 items and the thickness of copper is 1oz with filet. Take the most commonly-used green water soldermask ink for example.

  • Data accumulation method

  Damp film thickness tester is requested the dimension of thickness of soldermask. Because the test position is along the diagonal type of copper fingernails, the difference in conditions of spacing between copper fingernails leads to the variations on test array and test point. Take the nail with spacing of 5cm for example.

  To be able to have the data of dried out ink thickness, one nail of 5.0cm and one table for every type are ready. The dried out ink thickness data is read in the group of film thickness dimension test.

  Test Result Analysis

  • Ink uniformity for different toe nail distribution spacing

  Predicated on the evaluation on thickness of nail printing soldermask for different toenail distribution spacing, the soldermask thickness uniformity can be calculated based on the following method:


The relationship between the design of screen printing nail
  
The relationship between the design of screen printing nail

 

  The effect can be concluded as the comes after:

  a. For planks with the thickness of 0.8mm, the silkscreen ink thickness of nail with spacing of 5.0m between copper fingernails can reach 11%, which is preferable to that of 8.0cm and 10.0cm.

  b. For planks with the thickness of just one 1.5mm and 2.0mm, the silkscreen ink thickness of nail with spacing of 5.0cm, 8.0cm and 10.0cm between copper fingernails is almost the same.

  c. Suitable decrease in conditions of spacing between toe nail mattresses leads to apparent improvement of ink thickness uniformity of slim boards.

  • Moist film thickness change pattern of most test points

  Predicated on the evaluation on ink thickness change guidelines of every test point, the features of decreasing toenail distribution spacing leads to the next lead to enhance the soldermask thickness uniformity:

  a. Damp film thickness fluctuates with the changes of test positions. At the positioning with copper toe nail supporting in the bottom such as 1, 5, 9, 13, 21, 25, 29, damp film thickness is illustrated as the minimal value in the category. At the positioning definately not copper toenail supporter such as 3, 7, 11 (12), 15, 19 (20), moist film thickness is illustrated as the utmost value in the category.

  b. At the area with copper fingernails supporting, damp film thickness is relatively low with panel surface having no evident decrease while at the area definately not copper nail followers, moist film thickness is relatively high.

  c. Relatively great deformation requires place to slim boards along the way of silkscreen printing while relatively small deformation requires place to solid boards. Therefore, thicker planks with thickness of just one 1.5mm and 2.0mm are relatively smooth on the top.

  • Romantic relationship between damp film thickness and dimension position and assisting point

  The partnership between moist film thickness and dimension position and helping point can be summarized the following:

  a. For different spacing between toe nail distributions, the ink thickness of planks with different thickness raises with the improvement of the length between test factors and copper fingernails.

  b. The thicker planks are, small the change becomes with the improvement in conditions of the length between test factors and copper fingernails. Therefore, the rigidity of plank is relatively large and the distribution spacing can be relatively large.

  • Dried out ink thickness change on the top of board

  Dried out ink thickness change on the top of table can be concluded as the comes after - the change tendency of dried out ink thickness and damp film thickness is actually the same, indicating that under the same test conditions, it's suitable to replace dried out ink thickness with moist film thickness. However, because the test consequence of damp film thickness is greatly affected by the viscosity of ink, the thickness of moist film should be assessed within quarter-hour after silkscreen printing.

 Conclusion

  With bare copper planks with the thickness of 0.8mm, 1.5mm and 2.0mm and toenail bedrooms with copper toe nail spacing of 5.0cm, 8.0cm and 10.0cm, thickness of damp film and dried out ink is tested through mix matching with the next conclusion:

  a. Ink thickness uniformity can be evidently improved when spacing between toenail beds on slim planks (0.8mm heavy or thinner).

  b. Moist film thickness and dried out ink thickness maintain steady, indicating the acceptability of on-line dimension using moist film thickness tester and ink film thickness monitoring.


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