EP-4742841-A1 - A METHOD FOR TRANSFERRING A FUNCTIONAL MATERIAL

Abstract

The invention is aimed at providing a transfer method for a functional material (3) onto a receiving substrate (5). The method comprises the steps of: providing a plate (1) including at least one cavity (2), providing a functional material (3) followed by providing at least one coating (4) covering the functional material. Releasing the coated functional material by imparting an energy pulse (6) at the at least one cavity such that the functional material is transferred onto a receiving substrate. (5)

Inventors

• GIESBERS, Merijn Peter
• ARUTINOV, GARI
• Fledderus, Henri
• ROSO CASARES, Sergio
• KARKI, Akchheta

Assignees

• Nederlandse Organisatie voor toegepast- natuurwetenschappelijk onderzoek TNO

Dates

Publication Date

20260513

Application Date

20241112

Claims (17)

1. A method for transferring a functional material onto a receiving substrate by means of providing a transfer device for transferring the functional material onto the receiving substrate, said transfer device comprising: a plate having a cavity surface that includes at least one cavity, the method comprises: a. providing the at least one cavity with the functional material such that the at least one cavity is at least partially filled with the functional material; b. providing at least one coating, suitable for bonding to the functional material, on top of the functional material; c. releasing the coated functional material from the cavity by imparting an energy pulse provided at the at least one cavity, such that the functional material is transferred onto the receiving substrate; wherein the at least one coating provides a durable adhesion, with the receiving substrate, when transferred.
2. The method according to claim 1, wherein the at least one coating forms an interface layer between for the functional material and the receiving substrate.
3. The method according to claim 2, wherein the interface layer provides for additional functionalities comprising of improved wettability to the receiving substrate, improved conductivity, insulation, chemical resistance, vibration dampening, compressibility, stretchability, flexibility, coefficient of thermal expansion, recyclability, protection, degradation resistance, wavelength absorptivity, reflectivity, transmittance or any combination thereof.
4. The method according to any of claims 1-3, wherein the bond between the at least one coating and the receiving substrate is determined by a tack-value, wherein the tack value in due time is at least 70% of the initial tack value, the tack value measured according to ASTM D2979 .
5. The method according to any of claims 1-4, wherein the functional material is transferred after at least 15 min, preferably after 30 min, more preferably after 60 min.
6. The method according to claim any of claims 1-5, wherein the at least one coating does not interfere with the functional material.
7. The method according to any of the claims 1-6, wherein the functional material has a viscosity of at least 1 Pa.s measured according to the Brookfield method at 5rpm and 25 °C.
8. The method according to any of claims 1-7, wherein the transfer means is selected from the groups consisting of a laser, heat, UV or light.
9. The method according to any of claims 1-8, wherein the functional material comprises a solder paste, a conductive adhesive, a tacky flux, a dielectric material, a metallic ink, a conductive ink, a silicone, an underfill material, a solvent, a graphic ink, or any combination thereof.
10. The method according to any of claims 1-9, wherein the functional material is a conductive material, preferably the conductive material is selected from the group consisting from a solder paste, a conductive adhesive, a metallic ink, a conductive ink, or a combination thereof.
11. The method according to any of claims 1 - 10, wherein the at least one coating is selected from an adhesive, diluent, a solder paste, a conductive material such as a conductive adhesive or a conductive ink, a tacky flux, a dielectric material, a metallic ink, a silicone, a underfill material, a solvent, a graphic ink, or any combination thereof.
12. The method according to claim 11, wherein the at least one coating comprises a tacky flux.
13. The method according to any of claim 1 or claim 2, wherein the at least one coating is removed after the functional material is transferred to the receiving substrate..
14. The method according to any of claims 1 - 13, wherein the at least one cavity is 1 - 1000 µm deep and has a smallest diameter in a range between 1 and 5000 µm.
15. The method according to any of claims 1 - 14, wherein the thickness of the at least one coating is in the range of 0.1 - 100 µm.
16. A transfer device for transferring a functional material onto a receiving substrate, comprising: a. a plate having a cavity surface that includes at least one cavity; wherein the at least one coating covers the functional material; and wherein the at least one coating, by imparting an energy pulse at the at least one cavity, provides a durable adhesion with the receiving substrate such that the functional material is at least partially released from the at least one cavity onto the receiving substrate.
17. The device according to claim 16, wherein the at least one cavity further comprises a release layer.

Description

TECHNICAL FIELD OF THE INVENTION The invention relates to a transfer method of a functional material on a receiving substrate. BACKGROUND OF THE INVENTION In order to transfer functional materials such as a viscous material to a receiving substrate from a structured carrier using a laser, a resistive heater, a light source or a heat source, a carrier substrate may be coated or deposited with the functional material wherein the at least one cavity present on the carrier substrate may be filled using for example a squeegee. A typical example to transfer a functional material is when bonding an interconnection of discrete bare chip components of microelectronic components. A proper transfer of the functional material onto a receiving substrate is considered successful when the transfer is sufficiently accurate such that the predominantly miniature electrical or other types of interconnects are adequately bonded to the receiving substrate. In general the functional material is conductive such that electrical connection as well as the fixation may happen concurrently. Another typical process wherein a transfer of a functional material may be critical is when fixating and/or bonding dies in the semiconductor industry. A conductive material acting as a functional material, generally is referred to as a die attach material in the semiconductor industry, may be preferred as this may facilitate the removability of heat or may benefit the electrical conductivity of the bond between a die and a receiving substrate like for example a PCB-board. Functional materials often need to be formulated with other materials to increase the printability or coating properties. Often the functional material is combined with a solvent or a liquid such that an ink or a paste is formed. Ideally, a high solid content of the functional material is obtained or only a pure functional material is deposited on a receiving substrate. The high solid content of the ink or paste may accordingly increase the viscosity of the ink or paste possibly limiting a transfer of the functional material. To attain a sufficient accurate transfer, the tackiness of the functional material is considered a reliable parameter to measure transfer efficiency. Generally, a too low tackiness of the functional material may result in an unacceptable transfer or possibly may result in no transfer of the functional material, hence reducing the efficiency of the transfer process. Additionally, functional materials are regularly encountered with rapid drying due to, for example, the evaporation of a solvent present in the functional material. Consequently, material properties such as tackiness of a dried functional material may be affected and therefore may negatively affect the transfer accuracy and accordingly limit materials that can be used for bonding electrical connections. Further, some processes may require a stack comprising multiple materials to increase or provide a combination of functionalities. To provide a stack of multiple materials generally multiple prints need to be done. Multiple prints increase the processing time and may reduce to overall yield due to possible misprints or alignment inaccuracies between the different steps. Examples of transferring functional materials such as viscous materials can be found in US20170275750 and US20230209722. US20170275750 describes a method for transferring a functional material on a substrate using a pulse of light to heat the light absorbing material. US20230209722 describes a transfer method of a highly viscous material, such as a conductive paste, onto a receiving substrate. The transfer is achieved by heating a gas release layer. Both US20170275750 and US20230209722 describe a method for transferring a functional material but are silent about the yield loss and the lower transfer accuracy generally encountered when time progresses resulting in a gradual decline of material properties like for example tackiness of the functional material. As such, the prior art does not provide an acceptable solution or method to solve the yield loss and/or the decrease in accuracy for transferring a functional material. SUMMARY The present invention is aimed at providing a method for transferring a functional material onto a receiving substrate with an improved yield and/or accuracy. To improve the yield and/or the accuracy, the invention disclosed herein for transferring a functional material onto a receiving substrate is transferred by means of a transfer device comprising: a plate having a cavity surface that includes at least one cavity, the method comprising the steps of: providing the at least one cavity with the functional material such that the at least one cavity is at least partially filled with the functional material. After providing the functional material, at least one coating, suitable for bonding to the functional material, is provided on top of the functional material, forming a coated functional material. The at