SNARF for Doc 5842

SEMI International Standards
Standards New Activity Report Form (SNARF)

Date Prepared: 01/21/2015

Revised (if Applicable):

Document Number: 5842
SNARF for: New Standard: Test Method for Metal-Wrap-Through Solar Cell Via Resistance

Originating Global Technical Committee: Photovoltaic

Originating TC Chapter: China

Task Force (TF) in which work is to be carried out: Crystalline Silicon Solar Cell Task Force

Note: If a new task force is needed, also submit a task force organization form (TFOF)

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1. Rationale:
a. Describe the need or problem addressed by this activity.
(Indicate the customer, what benefits they will receive, and if possible, quantify the impact on the return on investment [ROI] if the Document is implemented.)
Metal-Wrap-Through (MWT) technology is one of the most effective solutions for reaching higher cell efficiency and higher module power output (Figure 1). Not only the cell efficiency is improved by reducing front side metallization area (without busbars any more), but also the ohmic losses of the module interconnection can be potentially decreased. Laser drilling of vias is one of the unique processes for MWT solar cells. Via metallization can then be done for electrical conduction.
MWT cells may be designed differently at both front (Figure 2) and back (Figure 3) sides.
Both front and back sides of MWT cells can be designed differently as shown above. However, the metalized vias are common to all MWT cells, which are shown in Figure 1.
The metallization within vias plays an important role for the performance of MWT solar cells because the generated current collected by the front fingers will be transferred through the vias to the rear side of the cells. If vias metallization is not fully optimized, there will be poor contact between the front finger and rear pad. This kind of contacts increases series resistance which results in the decreasing of the fill factor and finally bad cell performance. Methods to reduce series resistance of via metallization have been widely discussed in practice, including via paste modification, screen printing process, additional vacuum step during printing. Figure 4 shows the status of via hole at optimized and non-optimized conditions. When the cell was fabricated at non-optimized condition, fill factor dramatically dropped due to the high series resistance.
For both MWT cell manufacturers and MWT module makers, they need standardized test method to test electrical resistance of metalized vias.

b. Estimate effect on industry.
2: Major effect on an industry sector - identify the relevant sector
Sector or Company Information: MWT solar cell makers, MWT solar module makers

c. Estimate technical difficulty of the activity.
II: Some Difficulty - Disagreements on known requirements exist but developing consensus is possible

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2. Scope:
a: Describe the technical areas to be covered or addressed by this Document development activity. For Subordinate Standards, list common concepts or criteria that the Subordinate Standard inherits from the Primary Standard, as well as differences from the Primary Standard:
A test method based on single-sided 4-point measurement for metalized vias resistance of MWT soar cells.

b: Expected result of activity
New Standard or Safety Guideline (including replacement of an existing Standard or Safety Guideline)

For a new Subordinate Standard, identify the Primary Standard here:

For Standards, identify the Standard Subtype below:
Test Method

Miscellaneous (describe below):

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3. Projected Timetable for Completion:

a: General Milestones

a. Activity Start: 01/01/2015	b. 1st Draft by: 09/01/2015
c. (Optional) Informational Ballot by: 12/01/2015	d. Letter Ballot by: 03/01/2016
e. TC Chapter Approval By:06/01/2016

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4. Liaisons with other Global Technical Committees/TC Chapters/Subcommittees/TFs:
a. List SEMI global technical committees, TC Chapters, subcommittees, or task forces in your or other Regions/Locales that should be kept informed regarding the progress of this activity. (Refer to SEMI Standards organization charts and global technical committee charters and scopes as needed.)

b. List any planned Type I Liaisons with external nonprofit organizations (e.g., SDO) that should receive Draft Documents from Standards staff for feedback during this activity and be notified when the Letter Ballot is issued (refer to Procedure Manual § 7):

c. Intercommittee Ballots:
will not be issued

Identify the recipient global technical committee(s):

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5. Safety Considerations:
The resulting document is expected:

NOT to be a Safety Guideline

NOTE FOR "to be a Safety Guideline": When all safety-related information is removed from the Document, the Document is NOT technically sound and complete - Refer to Section 15.1 of the Regulations for special procedures to be followed.

NOTE FOR "NOT to be a Safety Guideline": When all safety-related information is removed from the Document, the Document is still technically sound and complete.

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6. Intellectual Property Considerations:
Note: Both a: and b: below should be checked for Revision of existing Standard(s) and Safety Guideline(s).

a. For a new Standard or Safety Guideline and for any part to be modified or added in a Revision of published Standards and Safety Guidelines:
the use of patented technology is NOT required.

If "patented technology is intended to be included in the proposed Standard(s) or Safety Guideline(s) " is selected above, then also check one:

b. For Revision, Reapproval, Reinstatement, or Withdrawal of existing Standard(s) and Safety Guideline(s):
there is no known material patented technology necessary to use or implement the Standard(s) and Safety Guideline(s)

c. The body of the Document and any Appendices, Complementary Files, Related Information sections, or Various Materials that may or may not be a part of the Document by reference:

NOTE FOR ‘the use of patented technology or the incorporation of Copyrighted Item(s) is NOT required’: If in the course of developing the Document, it is determined that the use of patented technology or Copyrighted Item(s) is necessary for the Document, the provisions of Regulations § 16 must be followed.

NOTE FOR ’will incorporate Copyrighted Item’: A copyright release letter must be obtained from the copyright owner prior to publication.

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7. Comments, Special Circumstances:
None.

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8. TC Member Review:
took place between (put dates below ) before approval at the TC Chapter Meeting, or

Member Review Start Date; 02/02/2015
Member Review End Date: 02/15/2015

NOTE FOR ‘TC Member Review’ is required by the Regulations for a period of at least two weeks
before approval of a new, or a major revision of an existing, Standard or Safety Guideline. (Refer to Regulations ś 8.2.1)
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9. SNARF Approval Dates:

TC Chapter or GCS	03/17/2015
Recorded in TC Minutes	03/17/2015

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10. SNARF Extension Dates:

TC Chapter Extension Granted on 10/25/2019

Extension Expires on 03/17/2020

TC Chapter Extension Granted on	10/25/2019
Extension Expires on	03/17/2020