DOC

Product Specification - LEKTRACHEM [TECHNIC UK] web site

By Charles Snyder,2014-01-11 12:27
14 views 0
Product Specification - LEKTRACHEM [TECHNIC UK] web site

    LEKTRACHEM LTD Liquid Photoimageable Solder Mask

    REVISION No 10

    ISSUE DATE: Wednesday, 24 March 2004

    ISR 1000 series solder masks are characterized as two component, photo definable coatings capable of being utilized in the manufacture of PWB’s as permanent protective coatings and resists for selective metalization of circuitry. Applied using screen-

    printing, curtain coating, and spray techniques, ISR 1000 series products exhibit the following performance properties:

     Excellent cosmetic appearance with a range of colours and surface finishes.

     Wide process latitude enabling fine image reproduction with clean PTH/Via development.

     Resolution capability below 2 mils for ultra fine pitch solder dams

     Resistant to multiple soldering operations.

     Superior resistance to all plated surface-finishing processes including ENIG, PB and Ag.

     Resistant to downstream processing chemicals including no-clean fluxes, cleaners, solvents, etc…

     Fully compatible with adhesives, under fills, and assembly rework processes.

     UL File #E83246, rated 94 V-0 with soldering limits of 20 seconds @ 288;C.

     Meets or exceeds IPC SM 840C, Bell core TR-NWT-000078, and MIL P55110D specifications.

Ink Preparation

    ISR 1000 series solder masks are supplied as pre-weighed, two component products in a mix ratio of 815:185, ink to catalyst. Briefly premix the individual components prior to addition of the catalyst into the ink. Thoroughly blend until a homogenous mixture is attained. Allow the mix to sit for ~15 minutes in its sealed container prior to use. Briefly remix, prior to use.

The usable pot life of the mixed material is 72 hours provided the material is stored in its original, sealed containers. Keep away

    from heat and strong light sources.

Panel Pre-cleaning

While pumice scrubbing using 3F or 4F grade is preferred, chemical or alternative mechanical scrubbing (e.g. AlO, silicon 23

    carbide brushing) will suffice provided the panels are uniformly clean and dry prior to solder mask application. For heavily stained/contaminated copper circuitry, a micro etch should be used before mechanical cleaning.

Sn/Pb circuitry should be degreased with a detergent based cleaning solution. Mechanical scrubbing, using equipment exclusively

    dedicated to Sn/Pb circuitry, will enhance adhesion by providing a roughened surface, thus enabling a physical bonding between the circuits and solder mask.

Application

Screen Printing

ISR 1000 series solder masks are formulated for use on all hand screening tables, single sided flat bed printers, and double sided

    screen printing apparatus. Follow equipment manufacturers recommendations for the operation of any automated screening equipment.

    Polyester meshes from 43T 62T should be used with a 65 70 shore squeegee. Screen tension should be uniform and a 2minimum of 30 N/cm. Flood /print sequencing should be used to ensure adequate fill between circuitry.

     LEKTRACHEM LTD UNIT 9 LIBERTY WAY, ATTLEBOROUGH FIELDS INDUSTRIAL ESTATE, NUNEATON, WARKICKSHIRE, CV11 6RZ, TEL: 02476 374999, FAX: 02476 374004 email: info@lektrachem.com

Air Spray, Elect6rostatic Spray and Curtain Coating

    Please contact the technical service department for guidance.

Tack-Dry

Exact drying times will depend on application technique and drying equipment utilized. For single sided processing, approximate

    convection oven times and temperatures are as follows:

Side 1 75/80;C (167/176;F) 20-30 minutes

    Side 2 75/80;C (167/176;F) 30 minutes

    Side 1 drying should be sufficiently tack-free to resist fingerprinting. Care should be taken when handling panels to prevent damage to side one during second side coating.

    Double sided coatings should be dried @ 75/80;C (167/176;F), for 35-45 minutes. Allow panels to cool to room temperature prior to imaging.

Weight Gain/Weight Loss

Weight Gain/Weight Loss analysis may be used to set-up and monitor (SPC control) the tack-dry process. This analysis provides a

    study of the weight percent of solvent lost from the solder mask coating during tack-dry. The weight percent of solvent lost from the solder mask during tack-dry should be 25% ? 0.5%.

The procedure for Weight Gain/Weight Loss is as follows:

    1) Weight an uncoated sample panel and record as the Weight Of Panel Uncoated.

    2) Coat the panel with solder mask using the approved LPSM coating method. Immediately reweigh the panel and record as

    the Weight of Panel Wet.

    3) Subtract the Weight of Panel from the Weight of Panel Wet and record as Weight of Solder Mask.

    4) Process the panel through the standard tack-dry process and allow to cool to room temperature. Weigh the panel and

    record at the Weight of Panel Dry.

    5) Subtract the Weight Of Panel Dry from the Weight of Panel Wet and record as the Weight of Solvent Lost.

    6) Divide the Weight of Solvent Lost by the Weight Of Solder Mask to determine the Percent of Solvent Weight Loss.

Calculations

Weight of Panel Wet Weight of Panel = Weight of Solder Mask

    Weight of Panel Wet Weight of Panel Dry = Weight of Solvent Lost

    Weight of Solvent Lost / Weight of Solder Mask x 100 = % Solvent Lost

Imaging

    A 5Kw or greater UV vacuum frame exposure unit should be used to properly polymerize the solder mask image. As the amount of exposure energy required to fully polymerize the solder mask film will vary depending upon mask color, thickness and proprietary formulation, proper exposure is determined through the use of a 21 step Stouffer step tablet. A properly exposed and

    developed solder mask film will exhibit a Stouffer step reading of solid 9-11.

The procedure for Stouffer step analysis is a follows:

    1) Ensure the Developing process is running properly (i.e. temperature, concentration, spray pressure, etc…).

    2) Coat a number of copper clad panel with solder mask and tack dry to completion

    3) Set developer speed to obtain a 20% breakpoint.

    4) Once developer process is set, set the exposure energy to obtain a solid Stouffer step reading of 9-11.

    5) Stouffer step reading may be monitored on a regular basis as part of an SPC program of process control.

     LEKTRACHEM LTD UNIT 9 LIBERTY WAY, ATTLEBOROUGH FIELDS INDUSTRIAL ESTATE, NUNEATON, WARKICKSHIRE, CV11 6RZ, TEL: 02476 374999, FAX: 02476 374004 email: info@lektrachem.com