Method for assembling patch type crystal oscillator

Abstract

The invention discloses a method for assembling an SMD (Surface Mount Device) type crystal oscillator, which solves the problem of filling layering, improves the product reliability and reduces the quality risk. The method is characterized in that a crystal oscillator is arranged on the outer side of a chip, the surface, provided with a crystal oscillator PAD, of the crystal oscillator faces upwards, the surface, not provided with a crystal oscillator PAD, of the crystal oscillator faces downwards and is supported on the surface of a substrate through an insulating glue layer, then the crystal oscillator PAD on the surface of the crystal oscillator and a corresponding chip PAD at the exposed position of the chip are connected through a bonding wire, the crystal oscillator PAD is communicated with the chip PAD, and the chip PAD is connected with the chip PAD. And finally, carrying out plastic packaging on the exposed surface of the crystal oscillator, the bonding wire and the exposed surface of the chip.

Description

Technical Field

[0001] The invention relates to the technical field of chip packaging, and in particular to a method for assembling a patch type crystal oscillator. Background Art

[0002] Crystal oscillators are increasingly used in circuits. Traditional crystal oscillator mounting is done through SMD mounting, which results in problems such as crystal tilt and solder voids. The bottom of the crystal oscillator is filled using UF technology. Due to the crystal tilt problem, there is insufficient filling in some areas during crystal filling, and the bonding strength between the filling material and the back of the crystal oscillator is not strong enough, resulting in filling stratification and reliability problems in the later use of the product.

[0003] The specific analysis is as follows: the existing ordinary crystal oscillator mounting method is SMD mounting, that is, a corresponding number of mounting PADs are set on the surface of the substrate, and then the crystal oscillator pins are mounted downward and outward after SMT printing solder paste. After the mounting is completed, it is soldered in a reflow furnace, and then chemical cleaning is used to remove the flux residue volatilized in the solder paste at the bottom of the device. After this mounting method is completed, the bottom of the device is suspended, and generally the bottom of the crystal oscillator needs to be filled with glue through the capillary action of UF glue. Due to the problems of warping and incomplete cleaning in the SMT mounting process, the bottom fill glue is not fully combined with the bonding surface of the crystal oscillator or the substrate during the UF glue bottom filling, which can easily cause the product to be delaminated during the thermal process, resulting in product failure.

[0004] Therefore, it is urgent to study a method to solve the filling and stratification of SMD crystal oscillators, so as to improve the filling and stratification problem of SMD crystal oscillators. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for assembling a surface-mount crystal oscillator, which improves its filling delamination problem, enhances product reliability, and reduces quality risks.

[0006] A method for assembling a surface mount crystal oscillator, characterized in that:

[0007] The crystal oscillator is set at the outer side of the chip, with the surface of the crystal oscillator provided with the crystal oscillator PAD facing upward, and the surface of the crystal oscillator without the crystal oscillator PAD facing downward and supported on the surface of the substrate through an insulating adhesive layer, and then the crystal oscillator PAD on the crystal oscillator surface and the corresponding chip PAD at the exposed position of the chip are connected through welding wires to connect the crystal oscillator PAD and the chip PAD, and finally the exposed surface of the crystal oscillator, the welding wires and the exposed surface of the chip are plastic-sealed.

[0008] It is further characterized by:

[0009] The specific steps are as follows:

[0010] S1. Place the surface of the crystal oscillator with the crystal oscillator PAD facing upwards;

[0011] S2, setting the surface of the crystal oscillator without the crystal oscillator PAD as the back side, with the back side of the crystal oscillator facing downward, and evenly coating the back side of the crystal oscillator with insulating glue to form an insulating glue layer, and the bottom of the insulating glue layer is adhered to the corresponding surface area of ​​the substrate;

[0012] S3, perform pressure welding on each crystal oscillator PAD to weld one end of the independent welding wire to the crystal oscillator PAD;

[0013] S4, welding the other end of the independent welding wire to the chip PAD corresponding to the crystal oscillator PAD;

[0014] S5. Perform plastic encapsulation mold flow filling on the crystal oscillator, chip, bonding wire and the surface of the substrate in the corresponding area, and fill and protect the exposed surface of the crystal oscillator, the bonding wire and the exposed surface of the chip.

[0015] It is further characterized by:

[0016] The crystal oscillator has two crystal oscillator PADs on both sides of the exposed surface, and the two crystal oscillator PADs correspond to the corresponding chip PADs at adjacent positions on the upper surface of the chip;

[0017] Preferably, the two groups of bonding wires in steps S3 and S4 are point-to-point connections between the crystal oscillator PAD and the chip PAD, except for the transition part in the height direction, to ensure that the bonding wires are relatively short, thereby ensuring a stable and reliable connection arrangement;

[0018] Preferably, the back of the crystal oscillator is completely coated with insulating glue, and the insulating glue layer formed by the insulating glue includes a partial outer expansion edge, and the outer expansion edge can reliably cover the back of the crystal oscillator. The crystal oscillator is reliably attached to the corresponding surface of the substrate through the insulating glue by the attachment pressure device, and the attachment pressure device ensures that the entire back of the crystal oscillator receives a uniform and reliable pressure, and ensures the consistency of the thickness of the insulating glue layer in the back area of ​​the crystal oscillator;

[0019] Preferably, the thickness of the insulating adhesive layer in the back area of ​​the crystal oscillator in a wet adhesive state is 25 μm to 50 μm.

[0020] After adopting the above technical solution, the surface of the crystal oscillator facing the substrate has been completely covered and evenly filled with insulating glue during mounting. After the crystal oscillator PAD and the corresponding chip PAD are connected and interconnected by welding wires, there is no need to fill the bottom of the crystal oscillator again. Only plastic encapsulation mold flow filling is required to fill and protect the crystal oscillator surface, welding wires and chip surface, so that the outer surfaces of the crystal oscillator, welding wires and chip are all covered with plastic encapsulation material. This improves the filling stratification problem, improves product reliability and reduces quality risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1It is a schematic diagram of the top view structure of the crystal oscillator assembly corresponding to the present invention (in the un-plasticized state);

[0022] Figure 2 The figure is a schematic diagram of the cross-sectional structure of the crystal oscillator assembly corresponding to the present invention (in the plastic-sealed state); the names corresponding to the serial numbers in the figure are as follows:

[0023] Crystal oscillator 10 , crystal oscillator PAD 11 , chip 20 , chip PAD 21 , insulating adhesive layer 30 , outer expansion edge 31 , substrate 40 , bonding wire 50 , transition portion in height direction 51 , and plastic packaging material 60 . DETAILED DESCRIPTION

[0024] A crystal oscillator uses a crystal that can convert electrical energy and mechanical energy into each other and works in a resonant state to provide stable and accurate single-frequency oscillation. The function of a crystal oscillator is to provide a basic clock signal for the system. Usually a system shares a crystal oscillator to facilitate synchronization of various parts. Some communication systems use different crystal oscillators for baseband and radio frequency, and synchronize them by electronically adjusting the frequency. There are two types of crystal oscillators: SMD and DIP, that is, patch and pin types. The SMD type crystal oscillator is mounted with the crystal oscillator solder point facing down, combined with the PAD on the surface of the substrate through SMD soldering, and the bottom of the crystal oscillator is filled with UF or mold flow. Due to the problems of contamination and crystal tilting in the SMD soldering process, the combination of the filler and the crystal oscillator is prone to insufficient strength and delamination.

[0025] The present invention provides a method for assembling a surface-mount crystal oscillator, wherein a crystal oscillator 10 is arranged at an outer position of a chip 20, a surface of the crystal oscillator 10 provided with a crystal oscillator PAD11 is arranged upward, a surface of the crystal oscillator 10 not provided with the crystal oscillator PAD11 is arranged downward, and is supported on the surface of a substrate 40 through an insulating adhesive layer 30, then the crystal oscillator PAD11 on the surface of the crystal oscillator 10 and a corresponding chip PAD21 at an exposed position of the chip 20 are connected through a welding wire 50, so that the crystal oscillator PAD11 and the chip PAD21 are connected, and finally the exposed surface of the crystal oscillator 10, the welding wire 50 and the exposed surface of the chip 20 are plastic-sealed.

[0026] In a specific embodiment, the crystal oscillator 10 has two crystal oscillator PAD11 on both sides of the exposed surface, and the two crystal oscillator PAD11 correspond to the corresponding chip PAD21 at adjacent positions on the upper surface of the chip 20.

[0027] The specific steps are as follows:

[0028] S1, facing the surface of the crystal oscillator 10 with the crystal oscillator PAD11 upwards;

[0029] S2, with the surface of the crystal oscillator 10 not provided with the crystal oscillator PAD11 facing downward, evenly apply insulating glue on the surface to form an insulating glue layer 30, the bottom of the insulating glue layer 30 is adhered to the corresponding surface area of ​​the substrate 40; the back of the crystal oscillator 10 is completely coated with insulating glue, and the insulating glue layer 30 formed by the insulating glue includes a partial outer expansion edge 31, and the outer expansion edge 31 can reliably cover the back of the crystal oscillator 10, and the crystal oscillator 10 is reliably attached to the corresponding surface of the substrate 40 through the insulating glue by the attaching pressure device, and the attaching pressure device ensures that the entire back of the crystal oscillator 10 is subjected to a uniform and reliable pressing force, and ensures the consistency of the thickness of the insulating glue layer 30 in the back area of ​​the crystal oscillator 10. The thickness of the insulating glue layer 30 in the back area of ​​the crystal oscillator 10 in the wet glue state after being pressed into place is 25μm to 50μm;

[0030] S3, performing pressure welding on each crystal oscillator PAD11 to weld one end of the independent bonding wire 50 to the crystal oscillator PAD11;

[0031] S4, welding the other end of the independent welding wire 50 to the chip PAD21 corresponding to the crystal oscillator PAD11. After welding, the two welding wires are independently connected to a group of crystal oscillator PAD11 and chip PAD21;

[0032] S5. Perform plastic molding mold flow filling on the crystal oscillator 10, the chip 20, the bonding wire 50 and the surface of the substrate 40 in the corresponding area, and fill and protect the exposed surface of the crystal oscillator 10, the bonding wire 50 and the exposed surface of the chip 20, so that the plastic molding compound 60 wraps the crystal oscillator 10, the chip 20 and the bonding wire 50.

[0033] The two groups of bonding wires 50 in steps S3 and S4 are point-to-point connections between the crystal oscillator PAD and the chip PAD, except for the transition portion 51 in the height direction, to ensure that the bonding wires 50 are relatively short, thereby ensuring a stable and reliable connection arrangement.

[0034] The principle is as follows: the surface of the crystal oscillator facing the substrate has been completely covered and evenly filled with insulating glue during mounting. After the crystal oscillator PAD and the corresponding chip PAD are connected and interconnected by welding wires, there is no need to fill the bottom of the crystal oscillator again. Only plastic molding mold flow filling is required to fill and protect the crystal oscillator surface, welding wires and chip surface, so that the outer surfaces of the crystal oscillator, welding wires and chip are all covered with plastic molding compound. This improves the filling stratification problem, improves product reliability and reduces quality risks.

[0035] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0036] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for assembling a surface mount crystal oscillator, characterized in that: The crystal oscillator is set at the outer side of the chip, with the surface of the crystal oscillator provided with the crystal oscillator PAD facing upward, and the surface of the crystal oscillator without the crystal oscillator PAD facing downward and supported on the surface of the substrate through an insulating adhesive layer, and then the crystal oscillator PAD on the crystal oscillator surface and the corresponding chip PAD at the exposed position of the chip are connected through welding wires to connect the crystal oscillator PAD and the chip PAD, and finally the exposed surface of the crystal oscillator, the welding wires and the exposed surface of the chip are plastic-sealed.

2. A method for assembling a surface mount crystal oscillator according to claim 1, characterized in that: The specific steps are as follows: S1. Place the surface of the crystal oscillator with the crystal oscillator PAD facing upwards; S2, setting the surface of the crystal oscillator without the crystal oscillator PAD as the back side, with the back side of the crystal oscillator facing downward, and evenly coating the back side of the crystal oscillator with insulating glue to form an insulating glue layer, and the bottom of the insulating glue layer is adhered to the corresponding surface area of ​​the substrate; S3, perform pressure welding on each crystal oscillator PAD to weld one end of the independent welding wire to the crystal oscillator PAD; S4, welding the other end of the independent welding wire to the chip PAD corresponding to the crystal oscillator PAD; S5. Perform plastic encapsulation mold flow filling on the crystal oscillator, chip, bonding wire and the surface of the substrate in the corresponding area, and fill and protect the exposed surface of the crystal oscillator, the bonding wire and the exposed surface of the chip.

3. A method for assembling a surface mount crystal oscillator according to claim 2, characterized in that: The crystal oscillator is provided with two crystal oscillator PADs on both sides of the exposed surface, and the two crystal oscillator PADs correspond to the corresponding chip PADs at adjacent positions on the upper surface of the chip.

4. A method for assembling a surface mount crystal oscillator according to claim 3, characterized in that: The two groups of bonding wires in steps S3 and S4 are point-to-point connections between the crystal oscillator PAD and the chip PAD, except for the transition portion in the height direction.

5. A method for assembling a surface mount crystal oscillator according to claim 2, characterized in that: The back of the crystal oscillator is completely coated with insulating glue, and the insulating glue layer formed by the insulating glue includes a partial outward expansion edge, which can reliably cover the back of the crystal oscillator. The crystal oscillator is reliably attached to the corresponding surface of the substrate through the insulating glue by a pasting pressure device. The pasting pressure device ensures that the entire back of the crystal oscillator receives a uniform and reliable pressing force.

6. A method for assembling a surface mount crystal oscillator according to claim 5, characterized in that: The thickness of the insulating adhesive layer in the back area of ​​the crystal oscillator in a wet adhesive state is 25 μm to 50 μm.

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