Soldermask question???

[backdrill]

I saw a PCB fabrication capability on soldermask:

Solder Mask

.LPI - Green, Yellow, Black, Red, Blue etc.
.Peelable Mask

Can someone help me understand the difference between an LPI soldermask and a Peelable Mask?
In what applications they are used?
What is the advantage/disadvantage between them?
Which is more costly and why?
What are the process involved in each type?

 

[babar_ali]

I understood the following after having a discussion with my friend who woks in a fabrication house.

Liquid Photoimagable Solder mask (LPI) soldermask is used for tight dimmensinal and tolerence control. LPI can be sprayed and curtain coated on to the PCB. It is then disclosed to a desired pattern (Term Photoimagable comes in to play) and developed to expose the opening to the desired pattern for parts to be soldered to the pads. The process goes to a thermal protection (cure) after the pattern is defined.

The peelalemask is screened to the already soldermask PCB to protect circuit from assembly or soldering operation. When these processes are over and the mask is no more needed it is mechanically (hands) removed and the area it used to protect is exposed for the final assembly process. peelable mask usually withstand chemical process (to some extent) and construction of all layers in HASL and ENIG finishes.

 

[backdrill]

What do you mean "The peelalemask is screened to the already soldermask PCB to protect circuit from assembly or soldering operation."
Does it mean that the pealable mask can be added to an existing soldermask?
Which of these method of adding soldermask of lower cost?
How are the performance/quality compared to each other?
How is the cycle time compared between LPI and peelable mask?

 

[marce]

Pealable mask protects parts of the PCb from solder during wave soldering, it is not a replacement for standard solder resist, so they cannot be compared as they perform different fuctions.
It is peeled of the PCB after wave/selective soldering to expose the protected part of the PCB. Used when components can gothrough wave soldering etc etc.

 

[backdrill]

Pealable mask protects parts of the PCb from solder during wave soldering, it is not a replacement for standard solder resist, so they cannot be compared as they perform different fuctions.
It is peeled of the PCB after wave/selective soldering to expose the protected part of the PCB. Used when components can gothrough wave soldering etc etc.

Do you know of any pcb fab shops capable of peelable masking?
In what applications are they used?
Can I assume that this peelable mask would be less applicable to manual soldering?

 

[D.A.(Tony)Stewart]

Dry masks are cheaper, Liquid masks are more precise and cost a bit more. Depends on layout DRC and cost goals for high volume.

LPI is better and there are 6 or more variations including gloss or matte finish.

 

[elle]

Hi! I have tried an online company that offers peelable mask. I needed it for my design. I assume that the peelable can also be applicable to manual soldering, but it can't be necessarily good at all instances.

 

[georgeg]

Peelable solder mask (PSM) is a temporary solder mask which is applied to a PCB prior to the Hot Air Solder Leveling (HASL) process. Its purpose is to protect gold plated surfaces from being coated with solder. PSM is manually removed after HASL. LPISM is permanent solder mask.

 

[marce]

PEALABLE MASK for customer boards is to mask holes and areas from solder during wave soldering, that is all, for manual soldering it is not required as you just dont solder the holes. If you dont use wave soldering you dont realy require it. It is generaly a blue colouredresist tht is quite thick in application and can be pealed off after use. Kapton tape can also be used.

 

[D.A.(Tony)Stewart]

You can also specify "filled" PTH with LPI , if specified on drawing for better vacuum pressure pin contacts for ATE large boards.