A FCCGA package device assembly process method

Abstract

The present invention discloses a method for assembling an FCCGA packaged device, comprising the following steps: applying solder paste to pads on a printed circuit board; mounting the packaged device; and soldering the packaged device. The mounted packaged device is subjected to vacuum vapor phase soldering, and the substrate temperature of the packaged device is controlled to be lower than the temperature of the printed circuit board to form a soldering temperature gradient between the substrate and the printed circuit board. The present invention reduces the risk of deformation of the packaged device during soldering, which could lead to solder column offset and shorting. This ensures that the FCCGA packaged device can be successfully assembled in one go, and that the soldering quality of the packaged device meets aerospace standards.

Description

Technical Field

[0001] The present invention relates to the field of aerospace technology, and in particular to an FCCGA packaging device assembly process method. Background Art

[0002] The FCCGA packaged device is a new type of packaging device for spacecraft payloads. FCCGA stands for Flip Chip-Colum Grid Array (FCCGA). The chip carrier of this new FCCGA packaged device uses an organic substrate, a metal heat sink is added to the chip, and short high-lead columns are planted on the organic substrate. The substrate and solder columns of this FCCGA device are connected with Sn63Pb37 solder. The device is assembled according to the soldering parameters in the manufacturer's product manual. The solder is Sn63Pb37 and the solder paste volume is 0.0437mm. 3 The entire board is welded using vacuum vapor phase reflow soldering, with single-step vacuuming during the welding phase and a peak welding temperature of 223.9°C.

[0003] During the soldering process of FCCGA packaged devices, a large number of device solder column short-circuit problems occur, resulting in low device assembly quality. The applicant has found through research that during the soldering process, as the soldering temperature continues to rise, the edge of the device packaging substrate warps and deforms, and the deformation gradually increases with the increase in temperature; at the same time, since the solder at the upper end of the device solder column is Sn63Pb37, Sn63Pb37 solder is also used when the device is soldered to the printed circuit board. When the temperature reaches 183°C, the solder at the upper and lower ends of the solder column melts at the same time, the deformation of the device body causes the solder column to be subjected to external force, resulting in the solder column being offset or short-circuited. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide an FCCGA packaging device assembly process method, which can avoid the short circuit of solder columns due to thermal deformation of the organic substrate, that is, to provide a simple, efficient and stable and reliable assembly process method.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] An FCCGA package device assembly process method comprises the following steps:

[0007] Apply solder paste to the pads of the printed circuit board;

[0008] Mounting the packaged device;

[0009] The packaged device is welded, and the mounted packaged device is subjected to vacuum vapor phase welding, and the substrate temperature of the packaged device is controlled to be lower than the temperature of the printed circuit board, so as to form a welding temperature gradient between the substrate and the printed circuit board.

[0010] In one embodiment, controlling the substrate temperature of the packaged device to be lower than the temperature of the printed circuit board includes:

[0011] A non-contact heat dissipation tooling is arranged outside the packaging device, and the top plate of the heat dissipation tooling is arranged above the packaging device. The lower half of the side wall of the heat dissipation tooling is hollowed out and the upper half is folded outward to form an opening for welding airflow to enter the heat dissipation tooling.

[0012] In one embodiment, the invention further includes: a heat dissipation structure composed of a plurality of overlapping heat dissipation fins is provided on the top plate.

[0013] In one embodiment, it also includes: hollowing out the lower half of the side wall of the heat dissipation tooling, folding the upper half outward at the same angle, and when a non-contact heat dissipation tooling is arranged outside the packaging device, making the distance between each side wall of the heat dissipation tooling and the packaging device consistent.

[0014] In one embodiment, the method further includes: coating solder paste on the pads of the printed circuit board, including: uniformly coating the solder paste on the pads, and the solder paste covers 85% of the entire area of ​​the pads.

[0015] In one embodiment, coating solder paste on the pad of the printed circuit board also includes: using a fully automatic screen printer and a steel mesh to print solder paste on the pad, the screen printing parameters are: scraper speed 25mm / s, scraper pressure 6KG, demolding speed 0.8mm / s, and steel mesh thickness 0.12mm.

[0016] In one embodiment, welding the packaged device includes:

[0017] After the printed circuit board is placed in the welding equipment, vacuuming is performed for the first time;

[0018] Then entering the soldering stage, the peak temperature on the printed circuit board is 205°C to 208°C;

[0019] Finally, vacuum the chamber a second time.

[0020] In one embodiment, the parameters of the first vacuuming are: vacuum degree 600 mbar, vacuum valve opening 50%, and vacuuming time 3 s; the parameters of the second vacuuming are: vacuum degree 700 mbar, vacuum valve opening 30%, and vacuuming time 2 s.

[0021] In one embodiment, before applying solder paste on the pads of the printed circuit board, the method further includes:

[0022] The printed circuit board and the packaged device are baked, and the printed circuit board is cleaned.

[0023] In one embodiment, after applying solder paste on the pads of the printed circuit board, the method further includes:

[0024] Check solder paste coating quality;

[0025] If the coating quality does not meet the preset conditions, the printed circuit board is cleaned and solder paste is re-coated on the pads of the printed circuit board;

[0026] If the coating quality meets the preset conditions, the packaged device is mounted.

[0027] The beneficial effects of the present invention are:

[0028] (1) A temperature gradient is formed between the packaged device and the printed circuit board, which reduces the deformation of the FCCGA packaged device body and ensures the first-time welding pass rate of the device.

[0029] (2) The number and thickness of the heat sinks in the heat dissipation structure can be adjusted as needed to facilitate the control of the temperature of the package body. At the same time, for different package bodies, the required welding temperature is different, which can also be adjusted by adjusting the number and thickness of the heat sinks, which has good scalability.

[0030] (3) By designing the solder paste amount, vacuum extraction timing, and welding process parameters, the temperature difference between the solder columns outside the package device and the solder columns inside is reduced, ensuring good wetting of the solder joints of the package device as a whole, reducing voids, and avoiding short circuits of solder columns. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings, wherein:

[0032] Figure 1 A schematic diagram showing a flow chart of an embodiment of the present invention is shown;

[0033] Figure 2 A schematic diagram showing a flow chart of another embodiment of the present invention is shown;

[0034] Figure 3 A schematic diagram showing the soldering of the packaged device of the present invention is shown;

[0035] Figure 4 A schematic structural diagram of a heat dissipation tooling according to an embodiment of the present invention is shown;

[0036] In the drawings, like reference numerals are used for like parts, but the drawings are not necessarily true to scale.

[0037] Reference numerals:

[0038] 1-Packaging device, 2-Solder column, 3-Solder paste, 4-Pad, 5-Printed circuit board, 10-Heat sink, 20-Heat dissipation tooling, 30-Substrate. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings.

[0040] Example 1

[0041] The present invention provides a FCCGA package device assembly process method, such as Figure 1 As shown, the following steps are included:

[0042] Step S10, applying solder paste on the pads of the printed circuit board;

[0043] Step S20, mounting the packaged device;

[0044] Step S30: performing vacuum vapor phase welding, controlling the temperature of the substrate of the packaged device to be lower than the temperature of the printed circuit board, so as to form a welding temperature gradient between the substrate and the printed circuit board.

[0045] It should be noted that if Figure 3 As shown, it shows the schematic diagram of FCCGA package device welding, where: Figure 3 Figure a shows solder paste 3 coated on pad 4 of printed circuit board 5, one end of solder column 2 contacts pad 4, the other end contacts device body 1, and solder column 2 is in a vertical state, that is, the current state meets the welding quality requirements. However, since the chip carrier of FCCGA packaged device uses an organic substrate, during the welding process, as the welding temperature continues to rise, the edge of the device package substrate warps and deforms, and the deformation gradually increases with the temperature rise; at the same time, since the solder at the upper end of the device solder column is Sn63Pb37, Sn63Pb37 solder is also used when the device is soldered to the printed circuit board. When the temperature reaches 183°C, the solder at the upper and lower ends of the solder column melts at the same time, the deformation of the device body causes the solder column to be subjected to external force, resulting in the solder column offset or short circuit, as shown in Figure 1. Figure 3 b. Figure 3 c and Figure 3 As shown in Figure d, the current state of the package body does not meet the welding quality requirements; during vacuum vapor phase welding, by controlling the substrate temperature of the packaged device to be lower than the temperature of the printed circuit board, a welding temperature gradient is formed between the substrate and the printed circuit board, so that both ends of the solder column can be soldered with the solder at a suitable temperature, and the substrate temperature above the solder column is lower than the temperature of the printed circuit board, making it less likely to deform and cause the solder column to shift and short-circuit, ensuring that the FCCGA package device is assembled successfully once and that the welding quality meets the aerospace standard requirements.

[0046] Example 2

[0047] The present invention provides a FCCGA package device assembly process method, such as Figure 1 As shown, the following steps are included:

[0048] Step S10, applying solder paste on the pads of the printed circuit board;

[0049] Step S20, mounting the packaged device;

[0050] Step S30: performing vacuum vapor phase welding, controlling the temperature of the substrate of the packaged device to be lower than the temperature of the printed circuit board, so as to form a welding temperature gradient between the substrate and the printed circuit board.

[0051] Specifically, in step S30, it includes:

[0052] Step S301: Install a non-contact heat sink outside the packaged device. Place the top plate of the heat sink above the packaged device. Hollow out the lower half of the heat sink's sidewalls, and fold the upper half outward at the same angle to form an opening for welding airflow to enter the heat sink.

[0053] Step S302: a heat dissipation structure composed of a plurality of overlapping heat dissipation fins is provided on the top plate.

[0054] Specifically, in step S301, the lower half of the side wall of the heat dissipation tooling is hollowed out, and the upper half is folded outward at the same angle. When a non-contact heat dissipation tooling is arranged outside the packaged device, the distance between each side wall of the heat dissipation tooling and the packaged device is made consistent, so that the substrate inside the heat dissipation tooling can be heated evenly, further preventing deformation during the welding process.

[0055] like Figure 4 As shown, a heat dissipation tool is shown, where both ends of the solder column are in contact with the substrate 30 and the printed circuit board 5 respectively, and the heat dissipation tool 20 is covered on the substrate 30, with its top plate located above the substrate 30 but not in contact with the substrate 30;

[0056] It should be noted that the lower half of the side walls around the heat dissipation tooling is hollowed out, and the upper half is folded outward to form an opening for the welding airflow to enter the heat dissipation tooling, that is, Figure 4 As shown, the welding airflow can directly contact the exposed solder column to ensure normal welding at both ends of the solder column. Since the substrate above the solder column is concealed by the heat dissipation tooling, the heat dissipation tooling absorbs part of the heat, so that the temperature of the substrate is lower than the temperature of the printed circuit board. Under the premise of ensuring the welding temperature, the substrate is prevented from being deformed by heat. At the same time, a heat dissipation structure composed of a plurality of overlapping heat sinks is provided on the top plate of the heat dissipation tooling. The number and thickness of the heat sinks can be adjusted as needed to facilitate the control of the temperature of the package body. At the same time, for different package bodies, the required welding temperature is different, which can also be adjusted by adjusting the number and thickness of the heat sinks, which has good generalizability.

[0057] Example 3

[0058] The present invention provides a FCCGA package device assembly process method, such as Figure 3 As shown, the following steps are included:

[0059] Step S10: put all the materials needed for assembling the FCCGA packaged devices into storage;

[0060] Step S20, baking the FCCGA packaged device and the printed circuit board;

[0061] Step S30, cleaning the pads on the printed circuit board;

[0062] Step S40: Use a fully automatic screen printer and a steel mesh to print solder paste on the pad. The screen printing parameters are: scraper speed 25 mm / s, scraper pressure 6 kg, demoulding speed 0.8 mm / s, overall steel mesh thickness 0.12 mm, local thickness of the FCCGA packaged device area is 0.15 mm, and opening diameter 0.7 mm.

[0063] Step S50: Check the solder paste coating quality by using a 20-40x microscope to inspect the solder paste to determine whether it meets the preset conditions;

[0064] If the solder paste coating quality does not meet the preset conditions, the pad is processed again according to step S30 and step S40;

[0065] If the coating quality meets the preset conditions, proceed to the next step;

[0066] The preset conditions are: the solder paste is evenly coated on the pad and covers 85% of the entire pad area;

[0067] Step S60: Mounting the packaged device, i.e., using the equipment to mount the FCCGA packaged device. During the mounting process, use a magnifying glass to check whether the substrate and the solder pillars correspond one to one and whether there is any misalignment.

[0068] Step S70, performing vacuum vapor phase welding, including:

[0069] Step S701: soldering the FCCGA packaged device using a vacuum vapor phase reflow soldering device. After the printed circuit board is fed into the soldering device, the first vacuum pumping is performed with a vacuum degree of 600 mbar, a vacuum valve opening of 50%, and a vacuum pumping time of 3 seconds.

[0070] Step S702, entering the welding stage again, the peak temperature on the printed circuit board is 205°C to 208°C;

[0071] Step S703: Finally, perform a second vacuuming operation with a vacuum degree of 700 mbar, a vacuum valve opening of 30%, and a vacuuming time of 2 seconds;

[0072] Step S80: inspect the packaged device after welding.

[0073] It should be noted that the FCCGA packaged device has a relatively large substrate size of 45mm*45mm, and is an organic substrate with a relatively small thermal capacity. The pin count is 1924, which is relatively dense. Therefore, during the soldering process, the applicant discovered that there was a temperature difference of more than 5°C between the peripheral pins and the inner pins. In this embodiment, the solder paste was evenly applied to the pads, and the solder paste was controlled to cover 85% of the pad surface area. The vacuuming and welding parameter settings before and after soldering reduced the temperature difference between the peripheral pins and the inner pins, thereby improving the quality of the packaged device.

[0074] Specifically, the welding process parameters are as follows:

[0075] Vapor phase liquid volume Injection 1 Injection 2 Injection 3 500ml 450ml 550ml Keep time Holding 1 Holding 2 Holding 3 115S 79S 47S Vacuum degree Opening Keep time Pre-vacuum 1 600mbar 50％ 2S Final vacuum extraction 1 700mbar 30％ 2S frequency Recycling time Final recycling 60Hz 35s

[0076] It should be noted that the peak temperature on the printed circuit board is controlled between 205°C and 208°C, rather than 210°C to 235°C as specified in conventional solder materials. That is, in this embodiment, the applicant has found that the use of the welding temperature, amount of solder paste, vacuum extraction timing, and welding process parameters described above to solder the FCCGA packaged device can significantly reduce the temperature difference between the outer solder columns and the inner solder columns of the substrate, thereby ensuring good wetting of the overall solder joints of the packaged device, reducing voids, and avoiding short circuits of the solder columns.

[0077] In the description of the present invention, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "back", "inside", "outside", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention.

[0078] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A FCCGA package device assembly process method, characterized in that: The following steps are involved: Apply solder paste to the pads of the printed circuit board; Mounting the packaged device; Welding the packaged device, performing vacuum vapor phase welding on the mounted packaged device, controlling the substrate temperature of the packaged device to be lower than the temperature of the printed circuit board, so as to form a welding temperature gradient between the substrate and the printed circuit board; Wherein, controlling the substrate temperature of the packaged device to be lower than the temperature of the printed circuit board includes: A non-contact heat dissipation tooling is provided outside the packaging device, and the top plate of the heat dissipation tooling is provided above the packaging device. The lower half of the side wall of the heat dissipation tooling is hollowed out, and the upper half is folded outward at the same angle to form an opening for the welding airflow to enter the heat dissipation tooling. When the non-contact heat dissipation tooling is provided outside the packaging device, the distance between each side wall of the heat dissipation tooling and the packaging device is consistent; a heat dissipation structure composed of a plurality of overlapping heat sinks is provided on the top plate.

2. The FCCGA package device assembly process according to claim 1, characterized in that: The method comprises coating solder paste on a pad of a printed circuit board, comprising: uniformly coating the solder paste on the pad, and the solder paste covers 85% of the entire area of ​​the pad.

3. The FCCGA package device assembly process according to claim 2, characterized in that: Coating solder paste on the pads of the printed circuit board also includes: using a fully automatic screen printing machine and a steel mesh to print solder paste on the pads, the screen printing parameters are: scraper speed 25mm / s, scraper pressure 6KG, demolding speed 0.8mm / s, overall steel mesh thickness 0.12mm, and the steel mesh thickness at the packaging device is 0.15mm.

4. The FCCGA package device assembly process according to claim 3, characterized in that: After applying solder paste on the pads of the printed circuit board, it also includes: Check solder paste coating quality; If the coating quality does not meet the preset conditions, the printed circuit board is cleaned and solder paste is re-coated on the pads of the printed circuit board; If the coating quality meets the preset conditions, the packaged device is mounted.

5. The FCCGA package device assembly process according to claim 1, characterized in that: Soldering the packaged device, comprising: After the printed circuit board is placed in the welding equipment, vacuuming is performed for the first time; Entering the soldering stage, the peak temperature on the printed circuit board is 205°C 208℃; Finally, vacuum the chamber a second time.

6. The FCCGA package device assembly process according to claim 5, characterized in that: The parameters of the first vacuuming are: vacuum degree 600 mbar, vacuum valve opening 50%, and vacuuming time 3 s; the parameters of the second vacuuming are: vacuum degree 700 mbar, vacuum valve opening 30%, and vacuuming time 2 s.

7. The FCCGA package device assembly process according to any one of claims 1 to 6, characterized in that: Before applying solder paste on the pads of the printed circuit board, it also includes: The printed circuit board and the packaged device are baked, and the printed circuit board is cleaned.

Images