Semiconductor package with individually molded leadframe and die coupled at solder balls
10204814 ยท 2019-02-12
Assignee
Inventors
Cpc classification
H01L2224/73204
ELECTRICITY
H01L2224/05571
ELECTRICITY
H01L2924/00014
ELECTRICITY
H01L2224/81193
ELECTRICITY
H01L2224/131
ELECTRICITY
H01L2224/13025
ELECTRICITY
H01L2224/97
ELECTRICITY
H01L2224/73204
ELECTRICITY
H01L24/97
ELECTRICITY
H01L2224/16225
ELECTRICITY
H01L2924/00014
ELECTRICITY
H01L2224/056
ELECTRICITY
H01L2224/16258
ELECTRICITY
H01L2224/32225
ELECTRICITY
H01L23/49861
ELECTRICITY
H01L2224/16225
ELECTRICITY
H01L21/563
ELECTRICITY
H01L23/49816
ELECTRICITY
H01L2224/81986
ELECTRICITY
H01L2224/131
ELECTRICITY
H01L2224/32225
ELECTRICITY
H01L2924/00
ELECTRICITY
H01L2224/97
ELECTRICITY
H01L2224/16257
ELECTRICITY
H01L2224/16227
ELECTRICITY
H01L24/73
ELECTRICITY
H01L2224/92125
ELECTRICITY
H01L2224/81986
ELECTRICITY
H01L2924/00
ELECTRICITY
H01L2221/68377
ELECTRICITY
International classification
H01L21/00
ELECTRICITY
H01L23/498
ELECTRICITY
Abstract
According to principles as taught herein, a leadframe array for a semiconductor die is prepared having locations to receive solder balls. Solder balls are then applied to the leadframe array, after which the leadframe array and solder ball combination is placed in a first mold and encased in a first molding compound. After the molding compound is cured, a layer of molding compound is removed to expose the solder balls. After this, a semiconductor die is electrically connected to the exposed solder balls. The combined semiconductor die and leadframe are placed in a second mold, and a second molding compound injected. The second molding compound flows around the semiconductor die and leadframe combination, fully enclosing the electrical connections between the leadframe and the semiconductor die, making the final package a twice-molded configuration. After this, the twice-molded semiconductor package array is cut at the appropriate locations to singulate the packages into individual products.
Claims
1. A method for making a semiconductor die package, comprising: forming recesses in a first surface of a leadframe array; placing solder in the recesses of the leadframe array to form solder balls; placing the combined leadframe array and solder balls into a mold; injecting a molding compound into the mold sufficient to fully encapsulate the solder and the first surface of the leadframe array to create a once-molded leadframe array; removing an upper portion of the molding compound and the solder balls sufficient to expose an interior surface area of the solder; attaching a semiconductor die to the exposed solder; placing the combined semiconductor die and once-molded molded leadframe array into a second mold; injecting a second molding compound into the second mold to encapsulate the semiconductor die and the upper surface of the exposed first molding compound; and singulating individual semiconductor die packages from the twice-molded semiconductor package array.
2. The method of claim 1, further including: attaching a solder ball to the semiconductor die prior to connecting the die to the once-molded leadframe array.
3. The method according to claim 2 wherein the connection of the semiconductor die to the once-molded leadframe array includes the step comprising: bringing the solder connected to the semiconductor die into physical contact with the solder of the once-molded leadframe array.
4. The method according to claim 1 wherein the second molding compound fully encapsulates the semiconductor die and the exposed portions of the once-molded leadframe array.
5. The method according to claim 1 wherein the second molding compound fully encapsulates the electrical connection between semiconductor die and the once-molded leadframe array without encapsulating one full surface of the semiconductor die.
6. The method according to claim 1 wherein the second molding compound fully encapsulates the electrical connection between the semiconductor die and the once-molded leadframe array, but does not encapsulate side walls or an exposed surface of the semiconductor die.
7. A method for making a semiconductor die package, comprising: forming recesses in a first surface of a leadframe array; placing solder in the recesses of the leadframe array to form solder balls; placing the combined leadframe array and solder balls into a mold; injecting a molding compound into the mold sufficient to fully encapsulate the solder and the first surface of the leadframe array to create a once-molded leadframe array; removing an upper portion of the molding compound and the solder balls sufficient to expose an interior surface area of the solder; attaching a solder ball to a semiconductor die; attaching the semiconductor die to the exposed solder after connecting the die to the once-molded leadframe array by bringing the solder connected to the semiconductor die into physical contact with the solder of the once-molded leadframe array; placing the combined semiconductor die and molded leadframe array into a second mold; injecting a second molding compound into the second mold to encapsulate the semiconductor die and the upper surface of the exposed first molding compound to create a twice-molded semiconductor die package array; heating the twice-molded semiconductor die array to a sufficient temperature to reflow the solder to merge the solder ball coupled to the die to the solder ball of the once-molded leadframe array to obtain an integral solder coupling between the semiconductor die and the leadframe; and singulating individual semiconductor die packages from the twice-molded semiconductor die package array.
8. The method according to claim 7 wherein the heating step is carried out prior to the semiconductor die being placed in the second mold and second molding compound injected therein.
9. The method according to claim 7 wherein the heating step is carried out after the semiconductor die has been removed from second the mold and second molding compound encapsulating it has been cured.
10. The method according to claim 8, further comprising: subjecting the solder coupled to the semiconductor die to a first temperature in the heating step to mechanically and electrically affix the solder of the die to the solder of the once-molded leadframe array; and subsequently carrying out the step of placing the semiconductor die and leadframe in the second mold and injecting the second molding compound, after which a second reflow temperature is carried out by subjecting the twice-molded semiconductor package array to a second temperature higher than the first temperature to carry out a second reflow to more completely combine the solder ball of the semiconductor die with the solder ball of the leadframe array.
11. The method according to claim 7 wherein the heating step is carried out concurrently with the step of injecting a second molding compound into the second mold to encapsulate the semiconductor die and the upper surface of the exposed first molding compound to create a twice-molded semiconductor die package array.
12. A semiconductor package comprising: a leadframe having a first side and a second side, the lead frame including a lead; a first solder member connected to the first side of the lead; a first molding compound extending from the first side of the lead, the first molding compound encapsulating the first solder member and the first side of the lead; a semiconductor die having an electrical pad on a first surface thereon; a second solder member connected to the electrical pad of the semiconductor die and to the first solder member that provides an electrical connection from the semiconductor die to the lead of the leadframe; and a second molding compound that encapsulates the semiconductor die, the second solder member and is in direct physical contact with both the second solder member and the first molding compound.
13. The semiconductor package of claim 12 wherein the first solder member is a solder ball.
14. The semiconductor package of claim 12 wherein the first molding compound and the second molding compound are comprised of different materials.
15. The semiconductor package of claim 12 wherein the second molding compound encapsulates the sidewalls and the first surface of the semiconductor die but not a second surface of the semiconductor die that is opposite the first surface.
16. The semiconductor package of claim 12 wherein the second molding compound encapsulates the first surface of the semiconductor die but not the sidewall or a second surface of the semiconductor die that is opposite the first surface.
17. A The semiconductor package comprising a leadframe having a first side and a second side, the leadframe including a lead; a first solder member connected to the first side of the lead; a first molding compound extending from the first side of the lead, the first molding compound encapsulating the first solder member and the first side of the lead; a semiconductor die having an electrical pad on a first surface thereon; a second solder member connected to the electrical pad of the semiconductor die and to the first solder member that provides an electrical connection from the semiconductor die to the lead of the leadframe; and a second molding compound that encapsulates the semiconductor die, the second solder member and is in direct physical contact with the first molding compound wherein first solder member and the second solder member have been bonded to each other in a heat treatment to form a single, contiguous solder member.
18. A semiconductor package comprising: a leadframe having a first side and a second side, the lead-frame including a plurality of leads; a plurality of solder balls, one solder ball of the plurality being connected to the first side of each of the respective leads of the plurality of leads; a first molding compound connected to the first side of the lead, the first molding compound encapsulating each of the solder balls and the first side of each lead; a semiconductor die having a plurality of electrical pads thereon; a plurality of solder members connected to each respective electrical pad of the semiconductor die and also to respective solder balls, the solder members and solder balls forming single, contiguous metal connection between the semiconductor die and the leadframe; and a second molding compound that encapsulates the semiconductor die, the second solder member and is in direct physical contact with both the solder members and the first molding compound.
19. The semiconductor package of claim 18 wherein the first molding compound and the second molding compound form a unitary, contiguous molding compound.
20. The semiconductor package of claim 18 wherein the solder balls and the solder members are comprised of the same metal alloy.
21. The semiconductor package of claim 18 wherein at least two of the solder balls are connected to the same lead to electrically connect the two solder balls and two of the electrical pads on the semiconductor to each other.
Description
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
(1)
(2)
(3)
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(5)
(6)
DETAILED DESCRIPTION
(7)
(8) As can be seen in
(9) In the embodiment of
(10)
(11) The package 11, as shown in
(12) The low-profile package 11, as shown in
(13) Alternatively, if an ultrathin, extremely low-profile package 11 is desired, then the removal of the package can continue significantly past when the semiconductor die 12 is exposed, to remove substantial portions of the semiconductor die 12, together with the molding compound 27. Namely, the blanket removal of the top side of the package can continue to remove a significant height of the semiconductor die 12 along with the molding compound 27 to substantially reduce the profile of the overall package. In this embodiment, an ultrathin package can be obtained, in which the semiconductor die 12 has approximately half or even one-third of its standard height, and the molding compound 27 is flush with the top of the semiconductor die 12 in the final ultrathin package 11, as shown in
(14)
(15) The embodiment of
(16)
(17)
(18) Layer 20 is applied as a blanket layer to the exposed surface of the leadframe 18 and patterned and etched to a desired pattern as shown in
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(21) The removal of the molding compound 24 and the top portion of each solder ball 22 can be achieved by any acceptable technique, milling being a preferred technique. It can also be removed using sawing, polishing, etching (either wet etching or dry etching), grinding, or other acceptable technique in order to remove the upper portion of molding compound 24 along with a portion of each solder ball 22.
(22)
(23) The combined semiconductor die 12 and once molded leadframe 18 are placed in a second mold. After being placed in the second mold, a second molding compound 16 is injected into the second mold to fully encase the semiconductor die 12 and also to bond with the first molding compound 24. The second molding compound 16 is selected which will strongly adhere to and firmly mold to the first molding compound 24. In some embodiments, the second molding compound 16 may become a unitary, contiguous molding compound with the first molding compound 24 at their junction such that the line between them is virtually invisible and indistinguishable. The twice-molded assembly is provided by taking the first-molded leadframe 18 having the first molding compound 24 thereon and placing it into a second mold and then subjecting it to a second molding step, with the semiconductor die 12 attached in order to encapsulate a second time the leadframe 18 and for a first time the semiconductor die 12.
(24) After the second molding step as shown in
(25)
(26) In one alternative embodiment, the reflow step is carried out when the assembly is in the condition as shown in
(27) In one preferred embodiment, the reflow occurs in two separate steps. In a first step, a first, minimal reflow is carried out when solder bump 14 is first brought into contact with solder ball 22 in order to adhere the two solder balls to each other and provide a strong mechanical and electrical connection. A first, minimum temperature reflow occurs by slight heating of the leadframe 18 with the solder ball 22 attached so that upon the solder bumps 14 touching the heated solder balls 22 there is a slight merge between the solder balls bringing them into strong mechanical and electrical connection. Preferably, this initial connection is carried out just as the semiconductor die 12 is first placed on the leadframe array 18 as shown in
(28) The heating is performed by heating the leadframe 18 and solder balls 22, which, being made of metal, will easily transfer heat. Subsequently, the assembly is placed in the second mold and the second molding compound 16 injected. After the second molding compound has been injected, then a second, more complete and higher temperature reflow is carried out. The higher temperature reflow will be at a significantly high temperature so that the solders completely merge with each other as a single contiguous piece of metal. The second reflow will be a relatively high temperature compared to the first one, and often sufficiently high that the two solder materials 14, 22 become substantially liquid.
(29) If the high temperature reflow were carried out when the assembly is partially completed as shown in
(30) In the stages shown in
(31) After the second reflow is carried out, the leadframe 18 is etched on the back side with an etching fluid that is selective to remove the leadframe material 18, but not remove the metal layer 20. Preferably, the leadframe 18 is made of copper, or in one embodiment aluminum. A wet etch which selectively removes copper, but does not remove nickel or a nickel, palladium, gold layer combination is used. This wet etch will remove the exposed copper portions of leadframe 18 so that some of the molding compound 24 protrudes through the bottom of the package, as can be seen in
(32)
(33) In step 46, solder 22 is attached to the leadframe array 18, usually as solder balls, but could be in another form as well. In step 48, the leadframe array 18 is placed into a first mold. Molding compound is injected to completely surround the solder balls 22, so they are fully encased and also to cover the top surface of the leadframe array 18. Subsequently, in step 52, the top of the completed molded leadframe is removed so as to expose portions of the encapsulated solder ball. After the top layer is removed, the semiconductor die 12 is electrically connected at the appropriate locations to the respective solder balls of the leadframe array 18, as seen in step 54. At this step, a slight heating of the leadframe array 18 can take place in order to increase the adhesion or, alternatively, some adhesive material may be used that will conductively couple the die 12 to the leadframe array 18. After the appropriate number of semiconductor die are connected to the respective proper locations in the leadframe array 18, the combination is placed into a second mold in step 56. Subsequently, in step 58, the combination is encapsulated to affix the package which includes the leadframe array 18 and the semiconductor die 12 in a second molding compound. After this, the twice-molded packages are singulated into individual packages in step 60.
(34) Multiple embodiments have been shown for creating a twice-molded semiconductor package 10. The various embodiments may be combined with each other to achieve a wide variety of different packages according to the various alternative embodiments as taught herein.
(35) The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.
(36) These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.