Liquid Encapsulants

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Encapsulant Adhesives
Product	Application	Viscosity at 25°C (mPa.s)	Filler Type (Content)	Max Filler Size, um	Hardener type	Tg by TMA (°C)	CTE α1(ppm/°C)	CTE α2(ppm/°C)	Cure time (min)	Cure Temp °C	Available	Key attributes
Dam
Loctite ECCOBOND FP4451TD	BGA and memory	300,000	Silica (73%)	200	Anhydride	150	21	65	30 + 90	125+165	Yes	- Ionically clean - Tall dam - High thixotropic index
Loctite ECCOBOND FP4451	BGA and memory	300,000	Silica (72%)	-	Anhydride	155	22	-	30 + 90	125+165	Superseded by FP4451TD	- Designed for use with fill encapsulant LOCTITE ECCOBOND FP4450
Fill
Loctite ECCOBOND FP0087	Stress-sensitive devices and severe automotive environments	20,000 at 20 rpm	Silica (76%)	-	-	175	18	-	60 + 60	125 + 180	No	- Low stress and high flow with reduced warpage and cracking - Low CTE - Cavity & potting ring - Halogen-free
Loctite ECCOBOND FP4450	Automotive, BGA, memory, COB, SIP and SmartCard	44,000	Silica (73%)	120	Anhydride	155	22	72	30 + 90	125+165	Superseded by X	- Low stress and relatively high flow - Good moisture resistance and excellent chemical resistance - Excellent pressure pot performance on live devices up 500 hr. - Oven cure
Loctite ECCOBOND FP4450HF	Automotive, BGA, memory, COB, SIP and SmartCard	32,000 at 20 rpm	Silica (73%)	25	Anhydride	164	19	71	30 + 90	125+165	Yes	- Excellent chemical, corrosion and moisture resistance - High thermal stability - Very high flow and fine filler
Loctite ECCOBOND FP4470	BGA, CSP, and full array on low temperature co-fired ceramic (LTCC)	48,000	Silica (75%)	50	Anhydride	148	18	65	30 + 90	125+165	Yes	- MSL3 260°C capable - Excellent flow good for fine pitch wires and deep cavities - 260°C reflow capability for Pb-free applications
Loctite ECCOBOND FP4651	Automotive, BGA, memory, COB, SIP, SmartCard and chip array ceramic packages	130,000 at 20 rpm	Silica (82%)	50	-	150	11	50	60 + 90	125+165	Replaces FP4651	- Low stress - Low CTE - Easy to dispense - Excellent chemical resistance and thermal stability - Oven cure
Loctite ECCOBOND FP4654	MEMS and chip array ceramic packages	32,000 at 20 rpm	Silica (80%)	50	Anhydride	146	13	53	30 + 90	125+165	Yes	- Low stress and low CTE - Excellent chemical resistance and thermal stability - Jettable
Loctite ECCOBOND FP4802	BGA, CSP and full array on low temperature co-fired ceramic (LTCC)	80,000 at 10 rpm	Silica (72%)	50	Phenolic	50	20	100	30 + 90	125+165	Yes	- MSL2 260°C capable - Low warpage - Excellent flow good for fine pitch wires and deep cavities
Glob Top
Loctite ECCOBOND FP4323	COB and plastic PGA	220,000 at 2 rpm	Silica (65%)	-	-	174	28	-	240 or 60	150 or 170	No	- Low CTE for improved thermal cycling - Thixotropic - Excellent moisture and chemical resistance - Oven cure
Loctite ECCOBOND FP4460	Automotive, BGA, memory, COB, SIP and SmartCard	300,000 at 10 rpm	Silica (75%)	120	Anhydride	173	20	70	180	150	-	- Low stress and high flow - Improved work life - Good pressure pot performance with low shrinkage - Excellent moisture and chemical resistance - Oven cure
Loctite ABLESTIK 8387BM	High throughput encapsulation applications	14,000	PTFE, Silica	10	Hybrid Epoxy	122	88	168	5 or 60	150 or 100		- Non conductive - Black pigmentation for blocking stray light
Loctite ECCOBOND FP4660	CSP and low stress applications	120,000 at 5 rpm	Silica (80%)	-	-	135	13	56	30 + 90	125+165	-	- Low stress - Excellent chemical resistance and thermal stability - Jettable - Oven cure
Loctite ECCOBOND UV8800M	CSP, BGA and SmartCard	2,500 - 4,000 at 5 rpm	Silica (54%)	21	-	29	41	135	2 seconds	315 - 400 nm (UV)	Yes	- Good pressure pot performance with low shrinkage - Excellent surface cure with adhesion to a wide range of substrates - Accurate dispensing with excellent shape control - UV cure
Loctite EO7021	CSP, BGA and SmartCard	17,000 at 5 rpm	-	-	-	125	67	187	60 or 5	120 or 150	Yes	- One component - Fast oven cure at moderate temperatures

Liquid resins are used in two main ways in encapsulations processes: glob top and dam & fill alternatively known as frame & fill

Epoxy Mold Compound vs Liquid Encapsulation

There are two main ways to encapsulate a semiconductor device: transfer molding a thermosetting Epoxy Mold Compound (EMC) or using liquid encapsulation directly on the Printed Circuit Board (PCB). Encapsulation in EMC is better than liquid encapsulation for applications that require higher filler content, and for the same reason, volume for volume, EMC is usually cheaper than liquid.

Liquid encapsulation, on the other hand, has a high flexibility and low through put

Liquid casting is however much more flexible. EMC requires are large significant investment in molding machines and mold plates for specific devices which must produce large quantities before there is a return on that investment. Liquid encapsulation on the other hand has a high flexibility and low through put: meaning that it is best suited for a multiple diverse low quantity orders.

In general liquid encapsulation is used for LEDs and potting or encapsulating electronics in bare die mounting on printed circuit boards (PCB), otherwise known as chip on board (COB).

Another advantage of potting and encapsulating devices in liquids is that in general, the result is flatter and thinner than devices encapsulated by a transfer molding process around a lead-frame with EMC. The space requirements for devices will continue getting more and more stringent as the component density of devices increases. This trend makes encapsulation and potting in liquids a sure bet for the future.

Transfer molding EMC may also cause wire sweep: where the pressure of the flowing molten compound shifts the fine-pitched bonding wires connecting a die. Wire sweep can cause shorts and mutual inductance. Liquid encapsulation is applied from above and does not disturb bonding wires. That’s why it is the industry standard for larger or extra sensitive dies and chips.

Liquid resin encapsulation via the glob top process is a single step application process but is less precise than dam & fill

Liquid Epoxy: Viscosity and Thixotropy

Bare die may be mounted to the PCB with die attach but that’s not enough to protect them or their connecting wires from moisture, mechanical stress, temperature, and chemical corrosion. That’s why it makes sense to insulate and encapsulate them with a protective potting layer of liquid encapsulant.

The low viscosity of liquid encapsulants is good for flat smooth finishes.

In non-Newtonian thixotropic encapsulants thixotropy refers to the temporarily lower viscosity of an epoxy gel when shear, pressure, or temperature is applied. This means that they can be gel-like when at rest, but flow like a liquid when agitated.

Being able to control the viscosity of liquid encapsulants means you can dial in how far they will spread over a surface area, and also how high they will build up to. This is important in Glob Top encapsulation where devices are literally encapsulated by a “Glob” from above.

Dam & Fill or Frame & Fill is a two step encapsulation process that is a little like 3d printing

Glob Top vs Dam & Fill

Glob Top is a process of encapsulation by using a fluid encapsulant gel with higher viscosity so that it fully encapsulates a device without flowing beyond the necessary area. As mentioned, by controlling the temperature, shear, and pressure, the viscosity and flow of liquid can be adjusted so that the final surface area and height of the “Glob” can be controlled quite effectively.

Dam & Fill on the other hand refers to a two-step process of encapsulation, where a ring or frame of higher viscosity liquid encapsulant is applied as a “Dam” around a device, and then a lower viscosity liquid “fill” is used to then fully encapsulate a device. The liquid used to build the frame or dam usually has more abrasive filler and a higher viscosity at rest than the liquid used for the fill.

Dam & Fill is a more selective protective coating and can be framed to cover areas in specific shapes, and is for example also used for optical bonding. In optical bonding the frame or dam is used to create a space between the glass and the display or touch screen. Then an optically clear fill is used as an adhesive and fixative.

Liquid Encapsulation for LEDs and Optoelectronic devices:

Optically clear liquid encapsulation is also used for LED devices, and encapsulate optical or optoelectronic devices that require both a high level of light transmittance as well as a good level of mechanical protection. In a similar process to Glob Top encapsulation, a literal glob of clear encapsulant is dropped directly into place on top of the LED. In another production process, optically clear liquid encapsulant is used to cast LED’s final body. Phosphor, colored dyes, and diffusant concentrates can be added to the liquid encapsulant to alter its optical properties.