Silver Paste

For front and back side silver conductors for (c-Si) crystalline solar cells

Better yields and higher outputs for solar cell manufacturers

In partnership with Heraeus, Targray offers the HeraSol Ag Paste compositions. The HeraSol compositions are a series of screen printable front and back side silver conductors for crystalline solar cells. Our compositions are all cadmium-free and tailored solutions for either SiNx or TiOx anti-reflective coatings. Lead free formulations are also available. All HeraSol Silver Pastes are co-fireable with commercial back side Ag/Al Pastes.

The HeraSol front side Ag Pastes are ideal for lightly-doped emitter designs and optimized for high throughput processing to deliver excellent aspect ratios and fine line resolution. For back side Silver Paste applications, the new lead-free Ag Paste significantly lowers material consumption due to high coverage and excellent initial and soldered age adhesion.

These Silver Metallization Pastes are customizable to your process, thus increasing efficiency and fill factor while providing wider processing windows.

Front Side Ag Paste Properties:

• Capture higher efficiencies and wider processing window
• Achieve a higher aspect ratio
• Excellent fine line resolution
• Low contact resistance on lightly doped emitter
• Cd free
• Pb free available
• Applicable to a wide range of sheet emitter wafers

Back Side Ag Paste Properties:

• Increased adhesion
• Co-firable with back Aluminum and front Silver pastes
• Greater peak adhesion strength
• Increased paste coverage with superior results provides a high quality, cost effective solution

Customized Ag Paste Solutions

Heraeus has been producing Silver Pastes for over 40 years and is well known for product customization. They can take advantage of the latest technologies and develop products that incorporate your unique wafer design and processes. Contact Targray and we will have our experienced technical product manager work closely with Heraeus' research and development engineers to customize an Ag Paste that will help you meet your goals in production and new product introduction.

Metallization Pastes for Conventional c-Si Solar Cells
Pastes	SOL952	SOL953	SOL9235H(L)	SOL9273M	SOL9318	SOL230(x)***
Description	Front-side Ag conductive paste	Front-side Ag conductive paste for high sheet resistance emitter	Front-side Ag conductive paste	Front-side Ag conductive paste	Pb-Free front side Ag conductive paste	Back-side Ag paste for solderable busbar application
Sheet resistance applicable	≤ 70 ohms/sq	≤ 80 ohms/sq, shallow emitter	≤ 70 ohms/sq	≤ 80 ohms/sq, shallow emitter	< 70 ohms/sq
Glass frits	Cd free	Cd free	Cd free	Cd free	Cd free, Pb free	Cd free, Pb free
Viscosity*	180 – 240 kcps	180 – 240 kcps	320 – 360 kcps (280 – 320 kcps)	330 – 370 kcps	300 – 350 kcps	100 – 160 kcps
Solids content	84.0 ± 1%	84.5 ± 1%	89.5 ± 1%	89.5 ± 1%	89.0 ± 1%	71.5 ± 1%
Solderability	Sn62 / Pb36 / Ag2 or Sn96.5 / Ag3.0 / Cu0.5
Wafer types	monocrystalline and multicrystalline silicon
Wafer surface treatment	Textured	Textured	Textured	Textured	Textured	Textured/planar
Anti-reflection coating	SiNx:H	SiNx:H	SiNx:H	SiNx:H	SiNx:H
Print screen	280 – 325 mesh S/S screen
Screen emulsion thickness	15 – 25 µm	20 – 25 µm	20 – 25 µm	20 – 25 µm	20 – 25 µm	10 – 15 µm
Drying	150 °C for 10 minutes in circulated air oven or 250 - 300 °C for 20 seconds in belt dryer
Firing	IR belt furnace, Spike Fire
Peak firing temperature** (not setpoint temperature)	740 – 800 °C	740 – 800 °C	740 – 800 °C	740 – 800 °C	740 – 800 °C	725 – 825 °C
Printed thickness (after fired)	15 – 20 µm	15 – 25 µm	20 – 30 µm	20 – 30 µm	15 – 25 µm	5 – 12 µm
Thinner	RV – 354					RV – 507
Shelf lifetime	6 months
Storage	5 – 25 °C  - Do not refrigerate
Usage	Allow paste to come to room temperature prior to opening - Spatulate well before using
*Brookfield HBT, SC4-14 Spindle in 6R Utility Cup @ 10 rpm **Peak firing temperature measured with type-K, 20 gauge thermocouple on surface of wafer. Omega #KMQXL-020G-18 ***SOL230(x): (M)-North America, (H)-Europe, (S)-Asia, (T)-Pb containing