soldermask process is an important process in printed circuit board (pcb) industry. the main purpo of this process is to apply a non-conductive coating on the surface of the pcb, which is ud to protect the circuitry on the board from damage in later stages of processing. usually, it is responsible for the board green appearance.
normally, the soldermask process includes the following process stages:
stage remarks
surface clean i/s,jet-scrubber英文昵称>四级预测
hysol plug-f* thermal cure ink
hysol ink cure*
surface clean i/s, jet-scrubber
lpi ink plug-f*
lpi plug-f cure*
lpi pre-coat*
lpi pre-coat cure*
二级建造师注册s/m coating
exposure diazo, silver halide film
developer
carbon ink print*
carbon ink pre-cure*
legend print*
alarmedplug-f cure, final cure*shrek
peelable *
peelable cure*
hal,gold,silver
stamp,route
e.t.
peelable*
peelable cure*
visual
packing
* skip stages when they are not required.
s/m process definition
1. surface clean
cleaning of copper surface by means of micro-etch and roughening by abrasion of brushing with aluminum oxide powder or high-pressure jet spraying.
panel is then d.i. rind and heated air dried for s/m plugging or coating on surface.
drain是什么意思this is the most important foundation for s/m adhesion. anything less done on this operation will result in s/m peeling after thermal shock at metal deposition process of hal, or even gold plating.
2. hysol plug-f
plugging of via hole using hysol ink as per customer requirement using horizontal mesh printing table with doted screen.
key control of this stage is to have maximum 2 print with 80-100% wet volume fill.
this is to minimize solder ball entrapment in via-f at hal process.
3. hysol ink cure
a 2 stage curing process is ud to fully cure hysol ink being plugged in via hole.
1st stage of lower temperature (210f, 90min) is to allow air entrapped in via hole and solvent in ink system to escape before a 2-stage hardening on surface has taken place.
without a 1st stage cure, ink in hole will flow out at the 2nd stage cure and cover any pad around via hole.
在线英文翻译
4. lpi ink plug-f
plugging of via hole using lpi (liquid photo imagable) ink when thermal hysol ink is not possible (via to pad < 40 mils)
key control is maximum 2 print to have 90-100% till depend on customer requirement of either solder ball is allowed to have in via hole.
panel is loaded directly to s/m coating m/c without any pre-cure.
5. lpi ink plug-f cure
this process is to tack dry the lpi plug hole ink to avoid the ink adhere to any contacting surface, especially when the sub lpi pre-coat process is needed, otherwi, the plugged panels will be nt to the coating machine for coating directly, and then this process is combined with the final cure and located at the s/m last stage. but it must be emphasized that the curing time will change from 10mins to 90mins to achieve fully hardened plugging ink in the via holes.
6. lpi pre-coat
printing s/m lpi ink on definite panel surface is lpi pre-coat. depending on the different targets, the printing area can be copper traces or copper edges or some definite laminate area or the whole panel area.
it has the same process, as lpi printing only the aim is different.
usually, if the naked panels have very high copper traces or if the designer wants to reduce the impendence value, pre-coat on copper traces will be applied, this process can avoid the skip problem during the coating process and the impendence failure problem before the boards are shipped to customers.
if the ink coverage on copper edge is required, pre-coat on copper edge can be ud. like the high ba copper panels.
if the lpi ink is ud to cover any press or inner layer defects, pre-coat on some definite areas is applied. and if the whole panel needs a more thicker s/m layer, do the pre-coat on the whole panel surface. at this point, it also can be regarded as lpi printing.
7. lpi pre-coat cure
the object of this process is to achieve a dried lpi pre-coat ink surface to avoid the ink to be sticked to the any contacting surface. 160f, 10mins are the most ud parameters. this process only will be applied if the two sides pre-coats are needed, otherwi the single side lpi pre-coated panels can be coated directly without any more tack drying.
8. s/m coating
coating/covering the entire panels surface with lpi ink, this can be done either one side at a time at manual printing table or 2 side at a time using dp system with vertical dual side screen, accumask electrostatic spray and dsa compress air atomizing spray.
lection of m/c mostly is dependent on ink thickness required and tending or covering of via hole is a customer consideration.
for s/m thickness control < 1.0 mil maximum on copper ground, us dp system.
for s/m thickness control <1.5 mil maximum on copper ground and not via should be tended, u dsa or accumask spray.
for s/m thickness cover on traces to be above 0.5-1.0 mil, u dsa spray system only.
panels after coated are then put in basket or rack to be dry either on its own system oven or stand alone tack dry oven of fuji or tc120 conveyor oven.
key control at this stage is wet thickness deposited and tack dry condition controlled to have a tacking free surface for s/m exposure,
9. s/m exposure
u.v. (ultra violet ray) light is ud to temporary harden ink surface through a photo tool in such that tho area needed to be clear of s/m is being tended by a/w pad and other area being expod by u.v. ray is harden for developing.
key control is u.v. energy level and life span of photo tool at optimum.
photo tool to keep below 225 exposure per t.
a/w stability and alignment different must keep within ±1 to 1.5 mils maximum.
10. s/m developing
developing of unexpod s/m away to “free up” copper pad for metal deposition at hal, silvers, gold and end tech.
介词有哪些media u is 1% na2co3 solution with dwell time of 90-120 c.
key control is to have a fully clean copper pad and at the same time not to over develop s/m fire dam to form dam lifting and big under cut that will hinder gold plating operation (enlarge gold plating on laminate due to entrapment at s/m under cut.
11. CARBON PRINTING
Printing of carbon paste on key contact finger per customer designated location.
Key control is to have a thick enough layer to have lower resistance on carbon paste at the same time not to smear “short” carbon finger to finger by optimizing printing pressure .
Alignment of mesh to panel must be good before any printing can be commenced.为什么要囤货
12.CARBON PRE-CURE
The object of this process is to achieve a dried carbon ink surface to avoid the ink to be adhered to the any contacting surface. This process only will be applied if the legend is needed or the other side carbon is needed, otherwi the single side carbon printed panels can be cured directly without any more tack drying, and can u the final cure programme .
13.LEGEND PRINT初中生物知识点
Printing of character, symbol, notation on panels surface .
Key control is to have a clear, readable character print out without smearing or blow of legend character by optimizing printing pressure with 1 printing only.
14. PLUG-F CURE, FINAL CURE
Stage curing for less ground area and multi step curing for panels that have massive ground plane.
Key is to slowly dry out moisture, solvent and air being entrapped during via hole pluggin
g before a final high temperature cure to fully harden surface s/m.
Lower temperature cure also allow air not to have sudden expansion that will push ink out from via holes and formation of “volcano” that will affect customer solder paste printing process.
15. PEELABLE S/M
A temporary “Peelable”S/M layer printed on special location for temporary protection against soldering or gold sliver deposition on this location.
Most of the time is gold pad plated before S/M operation that required a different gold thickness paled at other location or metal deposition of HAL, sliver and END TECH.
This layer is removable after metal deposition is completed.
16.PEELABLE CURE
Final curing of peelable s/m in box oven fully harden to protect area of interest and at the same time removable after metal deposition or asmbly purpo.
