Below is a list of some of the most frequently asked questions with answers.

Q1. Can the X35-186H-1 (two component) adhesion be improved with adhesion promoter
A1: The X-35-186H-1 has excellent adhesion characteristics to glass, metals and ceramics, and there is no need to add any adhesion promoter to this.

Q2. Can PMC be changed from 150C to 175C to decrease time?
A2:Yes, most probably 1hr would be OK at 175 degree C. We can provide data to support this.

Q3. Is there a significant effect for thickness differences between say 50um and a few milimeters?
A3:Most basic material performances don’t depend on the thickness.

Q4. What is the acceptable mixing ratio error allowed? (ie. 10:0.9 – 10:1.1)
A4: The acceptable error is +/- 2%, so 10 : 0.98 ~ 1.02 is the acceptable range

Q5: What is the pot-life of X35-186H-1?
A5: Shin-Etsu define potlife as being the time at 23°C at which viscosity increases more than 20%. 16 hrs is the specification.

Q6: Can the materials be supplied in pellets form?
A1: No. The compression molding materials are supplied in liquid form.

Q7: What is the required curing time on the molding machine & what is the full curing cycle
A7: The general starting recommendation is 90s @ 180C on the machine followed by 4 hours @ 150C post mold curing.

Q8: Are LPS 5547 & 5538 suitable for Metal Lead Frame molding – transfer or compression molding?
A3: Yes, the LPS-5547 and LPS-5538 are suitable for Metal Leadframes and compression molding. Neither material is suitable or can be used in transfer molding.

Q9: In case it comes only in liquid form – please advise for suitable mass production systems that are build for injection of pre-mixed molding material
A9: We have extensive experience and relationships with both TOWA and ASM for compression molding these silicones for LED devices, but we can support these activities with other suppliers also.

Q10: What about adhesion of LPS-5547 & LPS-5538 to Chips, Ceramics, Glass and other polymers
A10: Both the LPS-5547 and LPS-5538 have excellent adhesion characteristics to glass, metals and ceramics, and there is no need to add any adhesion promoter to this. As far as other polymers are concerned, these need to be tested on a case-by-case basis.

Q11: Are there materials that are suitable for transfer molding?
A11: Yes, Shin-Etsu have developed a line of highly reflective SWC transfer mold silicones for use as the reflector of the LED. These materials are transfer molded, but due to their highly complex and peculiar processing conditions, Shin-Etsu have taken this process in house and have agreed to supply the SWC ONLY as a premolded packages. These packages (known as “Tiger Leadframes” can be either metal leadframe, PCB or ceramic.

This list will be updated as questions are asked and data becomes available.

For more information regarding Shin-Etsu X35-186H-1 or any other Shin-Etsu silicone for LED assembly, please visit us or contact us for more details.

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CAPLINQ is proud to support Shin-Etsu in this highly specilized product line which uses traditional semiconductor industry transfer mold equipment to premold SWC grade silicone onto preplated leadframes (PPF). These premolded, preplated “Tiger” leadframes aim to completely replace the industry’s current PPA premolded package or substrate with a superior, cost-effective solution that can withstand high temperature and long-term UV exposure for LED and solar cell manufacturers.

Starting in 2010, Shin-Etsu plan to fully commercialize and sell these turn-key premolded leadframes that can withstand the much tougher requirements of high power LED applications and solar cell packages. Typically, ceramic packages have been considered as the only viable alternative to the industry standard PPA premolded plastic housings to withstand higher temperature and UV conditions.

For more information regarding Shin-Etsu premolded “Tiger” LF” leadframes, please visit us or contact us for more details.

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LINQTAPE PIT1S has a backing thickness of 1mil (25 micron) and the adhesive layer adds another 1.5 mil (36micron) for an overall thickness of 2.5mil (60 micron). The new PIT0.5S has a backing thickness of 0.5mil (13 micron) + 1mil (25 micron) adhesive layer for an overall thickness of 1.5 mil (38 micron).

This product is only available to registered users (customers can be added manually after registration) but the price is the same as LINQTAPE PIT1S.

To prepare a tape with an overall thickness of 25 micron could be possible, but the minimum order quantity would be one master roll of 20″ (510mm) width or the equivalent of about 20 rolls of 1 inch (25.4mm) tape.

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Q1. What’s the minimum polyimide film thickness?
A1. Our thinnest standard material is 1mil (0.025mm).  We can produce thinner, but there would be minimum order quantities associated.

Q2. Could we provide free samples of PIT1A?
A2. As you can imagine, CAPLINQ receives many, many requests for “free samples”.  The manual entries, paperwork and ultimately costs that resulted from working outside our current workflow system (ensuring correct ship-to addresses, price quotes, samples lists, follow-up, etc.) was not in line with the low-cost model that we try to bring to our customers.  As such, we have done away with minimum order quantities and implemented a way to order single units instead of shipping free samples.

Q3. What is the heat resistance? We require it above 200C for 1-2 hours.
A3. The temperature resistance depends on the application.  The polyimide film itself can withstand temperatures of 450 °F (~230 °C) and for short periods, can withstand temperatures as high as 900 °F (~480 °C).  The weak point is the adhesive system.  The silicone adhesive (PIT1S-Series) can maintain adhesion above 200C, as well as short (2-3 minutes) periods at 260C.  Above this temperature, adhesion drops off quickly.  Acrylic-adhesives (PIT1A-Series) have a lower temperature resistance, but at lower temperatures (Room temperature) have a higher adhesion than silicones.  Depending on the application (namely masking), it is quite reasonable that the PIT1S could withstand 200C for 2 hours.

Q4. Under a certain degree of temperature an pressure, would the glue be coming out from the edge?
A4.  It is imaginable that under pressure at high temperature that the adhesive layer is compressed.  Whether and how far it would come out from under the polyimide backing, we have no data for.

Q5. What is the lowest thickness that can be produced, and will the thickness influence its heat resistance ability?
A5. I need to check with production what the minimum thickness is, but no, heat resistance is independent of the film thickness.

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As can be seen in the photo below, there are also two variations on the Wafer Backside Coating Options also. The first figure on the left, there is the “no flow over wires” option. In this option, using Shin-Etsu SFX-513S the entire backside of the die is not coated and the wirebonding is either not affected during placement of the 2nd die, or the wirebonding is done in a subsequent stage in the process. In the second image on the right, using either Shin-Etsu SFX-524A Shin-Etsu SFX-526Aor the Wafer Backside Coating material does flow over the wires, and therefore needs to be liquid enough to pass over the wires during die placement and not cause any wire damage.

Wafer Backside Coating for Same Size Die Stacking: SFX-513S, SFX-524A and SFX-526A

Advantages of No Flow Over Wire (NFOW) Technique:

• Epoxy Molding Compound (EMC) completely encapsulates the wire with no risk of Coefficient of Thermal Expansion (CTE) mismatch between Die Attach (DA) and EMC
• Die Attach Operation can be done separately from Wirebonding

Disadvantages of No Flow Over Wire (NFOW) Technique:

• A non-uniform wafer backside coating is applied to each die – requiring stencil application

Advantages of Flow Over Wire (FOW) Technique:

• A uniform wafer backside coating is applied to each die, stencil printing or spin-coating is possible
• Entire Wafer can be coated
• In-line process of die-attach, wirebonding, die-attach, wirebonding is preserved

Disadvantages of Flow Over Wire (FOW) Technique:

• Epoxy Molding Compound (EMC) does not completely encapsulates the wire, so there is a risk of Coefficient of Thermal Expansion (CTE) mismatch between Die Attach (DA) and EMC
• Die Attach Operation can be done separately from Wirebonding

The difference between Shin-Etsu SFX-524A and Shin-Etsu SFX-526A is that Shin-Etsu SFX-524A contains no solvent and is therefore better suited for spin-coating, wheareas Shin-Etsu SFX-526A has solvent which helps it hold its shape better after stencil printing.

For more information regarding Shin-Etsu Die Attach SFX-513S, Shin-Etsu SFX-524A or Shin-Etsu SFX-526A please visit us or contact us for more details.

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KJR-4013E is a flexible, moisture-cure silicone most often used as junction-coating resins in the manufacture of diodes. KJR-651E, KJR-655E and KJR-657E are rigid thermoset polyimide-silicones used as junction coating resins in the manufacture of higher power diodes and thyristors. Both are used due to their excellent adhesion to epoxy molding compounds (EMC), high humidity resistance, and excellent volume resistivity and dielectric breakdown properties.

To be able to conduct failure analysis, customers have asked if there is a process to remove the cured silicone / polyimide-silicone from the diodes and/or thyristors (decap).

One recommendation is to use sulphuric acid (H2SO4) which can normally clearly strip organic compounds.  Nitric acid (HNO3) is another option.  If the dissolving rate is slow, adding heat to the process helps very much.  Of course, for either of these processes, a fume hood is necessary all the time.

For more information of copper wire bonding, visit us or contact us for more details.

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Silicone-based adhesives are certainly more standard, but sometimes the customer needs acrylic because they cannot have silicone in their systems, need higher adhesion at mid-range temperatures or other specific reasons.

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Our standard cure schedule recommendation for the Shin-Etsu KJR-651E is as follows:
150°C for 1hr + 200°C for 1hr + 250°C for 4 hrs

This is the minimum cycle required to drive out the solvents and get good cure characteristics.  However, this is only a recommendation; a good starting point.

Some manufacturers use a hotter, longer cure cycle such as :
110°C for 1hr + 200°C for 1hr + 250°C for 8hrs + 300°C for 4hrs + 380°C for 30 mins.

It has been determined by them that this is optimum cure cycle required to maximize performance and minimize current leak.  This has been confirmed by several customers who measure the gate leakage or leakage current at the maximum temperature of the junction test when the reverse voltage is applied.

These two cure conditions likely (but not definitely) represent the two extremes in cure conditions that customer could use to test the performance of their parts – especially to test for gate leakage at high temperatures.  Though the higher temperature may give better gate leakage parameters, the standard may give better adhesion characteristics.  Either way, these parameters ultimately need to be tested by the customer, ultimately testing both the adhesion characteristics and leakage current at the max temperature of the junction test.

For more information, please visit us or contact us for more details.

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Shin-Etsu offer a range of silicone materials suitable for optical fiber coating.

Depending on the equipment and method of polymerization (UV Cure of Heat Cure), different categories of products are available. Refer to the figure below.

Primary Coating Material

For the primary coating, there is one heat-cure product (OF-182), and two UV-cure products (OF-211 and OF-212). These products exhibit specific optical properties as the light (data) travels through this layer. For these applications a refractive index of 1.49 – 1.52 is required and all these products have refractive indices that fall in this range.

Buffer Coating Material

The buffer coating material is used to keep the light (data) within the fiber core and thus requires a material with a much lower refractive index, typically in the 1.41 – 1.44 range. For this application, there are two heat cure products (OF-101 and OF-180) and two UV-cure products (OF-207 and OF-208).

These materials are suitable for normal telecon fibers coated with 400µm – 500µm thicknesses at line speeds of 100 to 500 m/min.

For more information on these or other products, please visit us or contact us for more details.

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