Analysis of copper - free hole in PCB shallow
PCB manufacturing process is prone to shallow copper-free problem, some customers of this type
of hole without copper misjudged as follows:
1, tin light agent deep plating (to take place) poor ability to cause tin bad;
2, PTH abnormalities, the hole did not sink copper;
3, copper plating deep plating capacity is poor.
In the actual production, the thinner hole copper is not uncommon. The reason is nothing less
than the conductive substrate (plate a copper or thick copper layer) there is a hinder the plati-
ng of copper plating plating. The production and prevention of such a resist plating is analyzed
below.
In the process of developing a copper underneath a copper or a thick copper process, the
uncrosslinked polymer of the PCB is dissolved in the developer, and the developer containing the
ink polymer is sprayed again onto the PCB surface and the hole , At this time if the follow-up
pressure washing (including water quality) is not enough to PCB board and hole containing ink
residue residue washed, PCB proofing so that the residual ink polymer compounds will be in the
hole wall anti-sticky to form A thin layer of resistance plating, the more the central hole, the
worse the cleaning effect, the greater the probability of resistance plating layer, especially the
hole. (Multi-stage washing of the developing section is only a process of diluting the residue,
with the aim of diluting the residue as much as possible).
Understand the polymer anti-viscous coating is caused by the hole copper layer gradually bec-
ome the culprit, the focus of the problem to focus on the hole to ensure the cleaning effect to
remove the anti-sticky resistance coating. The right medicine, can cure.
In addition, the premise of dealing with the reality of the problem must be addressed, respect
for the customer's existing production conditions, such as: line and resistance welding, dry film
and wet film sharing machine, water flow by environmental restrictions.
There have been customers hope to increase the amount of micro-eclipse before the map can
remove the hole within the resistance plating, but unfortunately is nothing to do, and consequently
drop the micro-erosion over the hole and lead to copper. The correct solution should be to stren-
gthen the maintenance of the dry process maintenance, while the pre-treatment before the use of oil
removal effect of excellent acid degreasing agent.
EC-51 acid degreasing agent can cooperate with the customer to solve this kind of hole copper
from the hole to the center of the hole gradually thinner hole copper phenomenon, the correct use
of EC-51 acid degreasing agent should pay attention to the following matters:
1, EC-51 slightly less demanding water, requiring adequate washing, because it contains a
wetting agent may not clean copper cylinder and nickel cylinder can have more foam.
2, EC-51 designed for wet film, the use of wet film or black oil plate, if the hole is not
plated with nickel or copper, EC-51 treatment can be resolved. The dry line from the dry film shou-
ld be appropriate to reduce the amount of open cylinder, control EC-51 content of 4%, to prevent
excessive degreasing agent attack dry film line lead to canine tooth coating, in addition, EC-51
dry film gradually thin Hole no copper effect is also good.
3, the winter is the high incidence of such problems (due to low temperature, poor washing),
improve the effect of oil removal is the most effective way to increase the temperature (increase
the concentration of little contribution, but also increase the water pressure), the temperature
generally control 30- 35 degrees, too low temperature is not conducive to ensuring the effect of
degreasing; too high temperature prone to degreasing agent attack ink and lead to plating. PCB
manufacturing in the manual line, but also with the manual swing, install the filter to ensure
that the hole through the liquid. If the customer production conditions are poor, EC-51 cylinder
cycle should be shortened to 15-20 square feet / liter.
